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Dna based question

Dna based question


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We know that dna is an acid which is elaborated by deoxyribo nucleic acid.It has 4 nucleo bases.Now,the question arises, why dna has no uracil base?


First of all, uracil can be in DNA. Cytosine can spontaneously convert to uracil by a process called hydrolytic desamination. This causes guanine, which was originally bound to this cytosine, to be bound to uracil instead (remember: uracil normally binds to adenine). The next time the cell replicates its DNA, the place opposite this uracil would be occupied by adenine instead of guanine, correctly changing the information on this DNA section. This process of cytosine deamination is one of the most common DNA damage, but it is usually effectively corrected.

In DNA, thymine replaces uracil. Uracil can be produced relatively easily from cytosine by deamination and hydrolysis, which then alters (mutates) the base sequence and possibly alters the information genetically encoded in the nucleotide sequence.

Desamination of cytosine to uracil Thymine, on the other hand, differs from uracil in that it has an additional methyl group and thus cannot easily be formed from cytosine. Uracil present in the DNA can thus be recognized as a mutation and exchanged for cytosine by base excision repair.


The Question

A bacterial plasmid is 100kb in length. The plasmid DNA was digested to completion with two restriction enzymes in three separate treatments: EcoRI, HaeIII, and EcoRI + HaeIII (double digest). The fragments were then separated with electrophoresis, as shown.

a) Using the circle provided, construct a labeled diagram of the restriction map of the plasmid. Explain how you developed your map.

  • Recombinant DNA technology could be used to insert a gene of interest into a bacterium
  • Recombinant bacteria could be identified
  • Expression of the gene of interest could be ensured

c) Discuss how a specific genetically modified organism might provide a benefit for humans and at the same time pose a threat to a population or ecosystem.


Science Practice Challenge Questions

Describe structural and functional similarities between mitochondria and chloroplasts that provide evidence of common ancestry.

Explain how the structural and functional differences between mitochondria and chloroplasts provide evidence of adaptations among common ancestral organisms.

Examine the differences and similarities in the structural features of animal and plant cells. Justify the claim that both animals and plants have common ancestors based on your observations.

What conserved core processes are common to both animals and plants? Construct an explanation of the differences based on the selective advantages provided in different environments.

Louis Sullivan described architectural design as “form follows function.” For example, a window is designed to add light to a space without heat transport. A door is designed to allow access to a space. Windows and doors have different functions and so take different forms. Biological systems are not designed, but selected from random trials by interaction with the environment. Apply Sullivan’s principle to explain the relationship of function and form for each pair of cellular structures below.

  1. Plasma membrane and endoplasmic reticulum
  2. Mitochondrion and chloroplast
  3. Rough endoplasmic reticulum and smooth endoplasmic reticulum
  4. Flagella and cilia
  5. Muscle cells and secretory cells

Complex multicellular organisms share nutrients and resources, and their cells communicate with each other. A society may encourage cooperation among individuals while discouraging selfish behavior to increase the overall success of the social system, sometimes at the expense of the individual. Scientific questions are testable and often attempt to reveal a mechanism responsible for a phenomenon. Pose three questions that can be used to examine the ways in which a social system regulates itself. Be prepared to share these in small group discussions with your classmates about the similarities between these regulatory strategies and the analogous roles of plasmodesmata and gap junctions in cell communication.

Plasmodesmata in vascular plants and gap junctions in animals are examples of specialized features of cells. Mechanisms by which transport occurs between cells evolved independently within several eukaryotic clades. Explain, in terms of cellular cooperation, the selective advantages provided by such structures.

Mammalian red blood cells have no nuclei, must originate in other tissue systems, are relatively long-lived, are small with shapes that actively respond to their environment, and are metabolic anaerobes. Other vertebrates have red blood cells that are usually nucleated and are often relatively large, aerobic, self-replicating, and short-lived.

To connect these facts to biology, questions need to be asked. The questions that you pose will depend on the path your class is taking through the curriculum. Begin by summarizing what you know:

  • What are the functions of a eukaryotic cell nucleus?
  • What is the approximate average size of a human red blood cell?
  • What is the range of blood vessel diameters in adult humans?
  • What is the range of red blood cell size in vertebrates?
  • What is the average lifetime of a human red blood cell?
  • How can you show how cell production is stimulated using examples from particular systems?
  • How is cell death controlled?
  • What biochemical cycles are associated with anaerobic and aerobic respiration, and what are the important differences between these?
  • What process is involved in the transport of oxygen and carbon dioxide into and out of red blood cells?
  • What behaviors and dynamic homeostatic processes might be associated with the properties of red blood cells in mammalian and nonmammalian organisms?
  • What do you know about the evolutionary divergences among vertebrates?

Your summary has revealed some similarities and differences among vertebrate erythrocyte and circulatory system structures. Scientific questions are testable. They can be addressed by making observations and measurements and analyzing the resulting data.

  1. Pose three scientific questions that arise from your summaries of what you know about erythrocytes and capillary size.
  2. For each question you pose, predict what you believe would be the answer and provide reasoning for your prediction.
  3. Describe an approach you think can be used to obtain data to test your prediction.
  4. In the production of mammalian red blood cells, erythrocytes that have not yet matured and are still synthesizing heme proteins are surrounded by a macrophage. Predict the role of the macrophage in the maturation of a red blood cell.

Mitochondria have DNA that encode proteins related to the structures and functions of the organelles. The replication appears to occur continuously, however, many questions about control of replication rate and segregation during mitosis are yet unanswered. Many diseases are caused by mitochondrial dysfunction. Mitophagy, as the name suggests, leads to the destruction of mitochondria. Predict whether or not cellular control mechanisms involving the regulation of mitochondrial DNA by the nucleus exist. Make use of what you know about selection and homeostasis as they apply to both the organism and to the organelle.


Genetics Multiple Choice Questions and Answers

MCQ quiz on Genetics multiple choice questions and answers on Genetics MCQ questions quiz on Genetics objectives questions with answer test pdf for interview preparations, freshers jobs and competitive exams. Professionals, Teachers, Students and Kids Trivia Quizzes to test your knowledge on the subject.

Genetics MCQ Questions and Answers Quiz

  1. 22 autosomes and an X chromosome.
  2. 22 autosomes and a Y chromosome.
  3. 23 autosomes.
  4. 46 chromosomes.

2. The cytoplasm of an animal cell is divided by means of:

  1. A cleavage furrow.
  2. A cell plate.
  3. A cell membrane formed within the cytoplasm.
  4. Mitosis.

3. Which of the following is correct?

  1. A forms 2 hydrogen bonds with G T forms 3 hydrogen bonds with C
  2. A forms 3 hydrogen bonds with T G forms 2 hydrogen bonds with C
  3. A forms 2 covalent bonds with T G forms 3 covalent bonds with C
  4. A forms 2 hydrogen bonds with T G forms 3 hydrogen bonds with C

4. Which of the following may contribute to causing cancer?

  1. a mutation in a gene that slows the cell cycle
  2. faulty DNA repair
  3. loss of control over telomere length
  4. all of the above

5. Which of the following is not true of DNA?

  1. A pairs with T and G pairs with C
  2. Nitrogen bases are 0.34 nm apart on a DNA strand
  3. The double helix is 2.0 nm wide
  4. The double helix is 3.4 nm wide

6. Those mutations that occur by environmental damage or mistakes during DNA replications are

7. Why is sickle cell disease so called?

  1. because it makes people sick
  2. its named after a special type of white blood cell
  3. pH changes in the blood cells make them collapse into a sickle shape
  4. because its caused by an infectious microorganism that has sickle shaped cells

8. Those cancers that derived from ectoderm or endoderm of epithelial cell are called

9. During cell division there are three types of check points one of them (M checkpoint) to ensure


The Structure and Importance of Nucleic Acids

DNA and RNA, the nucleic acids, are the molecules responsible for the hereditary information that controls the protein synthesis in living organisms. The name “nucleic” derives from the fact that they were discovered (by the Swiss biochemist Friedrich Miescher, in 1869) within the cell nucleus. At that time, it was not known that those substances contained hereditary information.

Structure of Nucleic Acids

More Bite-Sized Q&As Below

2. What units make up nucleic acids? What are the chemical compounds that make up those units?

Nucleic acids are formed by sequences of nucleotides.

Nucleotides are composed of one molecule of sugar (deoxyribose in DNA and ribose in RNA) bound to one molecule of phosphate and to one nitrogenousꂺse (adenine, uracil, cytosine or guanine, in RNA and adenine, thymine, cytosine and guanine, in DNA).

3. What are pentoses? To what organic group do pentoses belong? Are nucleotides formed of only one type of pentose?

Pentoses are carbohydrates made of five carbons. Deoxyribose is the pentose that composes DNA nucleotides and ribose is the pentose contained in RNA nucleotides.

4. Into which two groups can the nitrogenous bases that form DNA and RNA be classified? What is the criterion used in that classification?

The nitrogenous bases that form DNA and RNA are classified as pyrimidine and purine bases.

Through the analysis of the structural formulae of those nitrogenous bases, it is possible to see that three of them, cytosine, thymine and uracil, have only one nitrogenized carbon ring. The others, adenine and guanine, have two nitrogenized bound carbon rings.

5. What is the difference between DNA and RNA from the point of view of the nitrogenous bases that are present in their nucleotides?

In DNA, nucleotides can be made up of adenine (A), thymine (T), cytosine (C) or guanine (G). In RNA, nucleotides can also contain adenine (A), cytosine (C) or guanine (G) however, instead of thymine (T), they contain uracil (U).

6. What parts of nucleotides bind to form nucleic acids? What is meant by the 5’ and 3’ extremities of nucleic acids?

The phosphate group of one nucleotide binds to the pentose of the other nucleotide and so on to make the polynucleotide chain.

Each extremity of a DNA or RNA chain can be distinguished from the other extremity by its terminal chemical entity. The phosphate-ended extremity is called a 5’-extremity and the pentose-ended extremity is called a 3’-extremity. Therefore, DNA or RNA chains can have a 5’-3’ or 3’-5’ direction. These directions are important for several biological functions of DNA and RNA, since some reactions specifically occur in one direction or the other.

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Where to Find DNA in Cells

7. Bacteria are prokaryotic cells, meaning that they do not have a membrane-enclosed nucleus. Eukaryotes have cells with am enclosed nucleus. Where in these types of cells can DNA be found?

In eukaryotic cells, DNA is found within the cell nucleus. In prokaryotic cells, DNA is found dispersed in the cytosol, the fluid space inside the cell.

Other DNA molecules can also be found within mitochondria and chloroplasts, specialized organelles of eukaryotic cells.

The Watson-Crick Model of DNA

8. Who were James Watson, Francis Crick and Maurice Wilkins?

Watson (American), Crick (British) and Wilkins (New Zealander) were responsible for the discovery of the molecular structure of DNA, the double helix made of two polynucleotide chains paired by their nitrogenous bases. They won the Nobel Prize in medicine in 1962 for the discovery.

9. According to the Watson-Crick model, how many polynucleotide chains does a DNA molecule have?

A DNA molecule is formed by two polynucleotide chains bound in antiparallel mode (5’-3’ to 3’-5’) and which form a helix structure.

10. What is the rule for the pairing of nitrogenous bases within the DNA molecule? What about in RNA molecules? Is this last question relevant?

The rule for the pairing of the nitrogenous bases of the polynucleotide chains that form DNA molecules is that pyrimidine base binds to purine base, under the condition that thymine (T) binds to adenine (A) and cytosine (C) binds to guanine (G).

In RNA, there is no binding between nitrogenous bases. That is because RNA is formed of only one polynucleotide chain, as opposed by DNA, which is formed of two chains. It is therefore not correct to ask questions about base pairing in RNA.

11. What is the numeric relationship between pyrimidine and purine bases in DNA molecules? Is this valid for RNA molecules?

DNA molecules are made of two bound polynucleotide chains that form a helix structure (the double helix). The binding of the two chains occurs between their nitrogenous bases and always obeys the following rules: adenine (A), a purine base, binds with thymine (T), a pyrimidine base and guanine (G), a purine base, binds to cytosine (C), a pyrimidine base. Therefore, in one molecule of DNA, there will be the same number of adenine (A) and thymine (T) bases and same number of cytosine (C) and guanine (G) bases. As a result, the quantities of purine and pyrimidine bases will also be the same, with a 50% proportion for each type. The rule A = T and C = G, or A/T = C/G = 1, is called Chargaff’s Rule, along with the pairing rules described above.

In RNA there is only one nucleotide chain. RNA is a simple chain molecule and, as result,  there is no need for the proportions of the nitrogenous bases that compose it.

12. Which type of chemical bond maintains the pairing of each chain in the DNA molecule?

To form the DNA molecule, purine bases bind to pyrimidine bases via intermolecular bonds called hydrogen bonds. Hydrogen bonds occur when there is a hydrogen atom near one of the following electronegative elements: fluorine, oxygen or nitrogen.

In such conditions, hydrogen appears to have lost electrons to those elements and a very strong polarization is created. The highly positive hydrogen atom attracts pairs of electrons from other molecules, making a hydrogen bond.

13. What is the complementary sequence of nitrogenous bases for an AGCCGTTAAC fragment of a DNA chain?

DNA Replication

14. What is the name of the DNA duplication process? What is the main enzyme that is involved in it?

The process of copying, or duplication, of DNA molecules is called replication. The enzyme involved in the formation of a new DNA chain is DNA polymerase. There are also other important enzymes in the replication process, such as helicase, gyrase and ligase.

15. Why is the statement that DNA self-replicates incorrect?

DNA is not completely autonomous in its replication process because the replication does not occur without enzymatic activity. Therefore, it is not entirely correct to claim that DNA self-replicates.

16. How do the two complementary nucleotide chains of DNA facilitate the replication process of the molecule?

The fact that the DNA molecule is made of two polynucleotide chains whose nitrogenous bases form hydrogen bonds facilitates the replication of the molecule. During DNA replication, the bond between the two chains is broken and each of them serves as a template for the formation of a new nucleotide sequence along it, with the help of the enzyme DNA polymerase and obeying the pairing rule A-T, C-G. At the end of the process, two double helices of DNA are produced, each made of an original template chain and of a new synthesized polynucleotide chain.

17. Which chemical bonds in DNA molecules must be broken for replication to occur?

During the DNA replication process, the hydrogen bonds between the nitrogenous bases of the polynucleotide chains are broken.

18. As a result of DNA replication, two DNA molecules come into existence. Why is it not correct to claim that two “new” DNA molecules are created? What is the name given to this?

During replication, each chain of the DNA molecule acts by pairing new nucleotides and, after the process, two newly formed chains made from the bond between these nucleotides appear. As a result, two DNA molecules are created, each with one chain from the original molecule and one new chain formed by new nucleotides. Therefore, it is not entirely correct to claim that the replication produces two new molecules of DNA. It is better to state that two new half-molecules are created.

Because of this phenomenon, DNA replication is called semiconservative replication.

19. Does DNA replication occur during cell division?

Yes. DNA replication occurs during mitosis as well during meiosis.

The DNA Repairing System

20. One characteristic of DNA molecules is their replication capability. What are the consequences of failures during DNA replication?

Ideally, a DNA molecule should replicate perfectly. However, sometimes failures in the replication occur, causing the alteration (deletion, addition or substitution) of one or more nucleotides in the molecule.

These mistakes, or mutations, also make changes in the protein synthesis process. For example, the production of an important protein for cells or tissues may be suppressed new useful or unusable proteins may be created, etc. Mistakes in DNA replication and the resulting creation of altered genetic material are some of the main creative forces behind biological evolution and the diversity of species.

21. Mistakes can happen during every copying process, and the same is true for DNA replication. Do cells have correction systems to fix those mistakes? When are these mistakes carried only by the individual within which the mistake occurred and when are they passed on to other individuals?

Cells are equipped with an enzymatic system that tries to fix mistakes in the DNA replication process. However, this system is not completely efficient.

DNA replication mistakes remain within the original individual in which the failure occurred when the phenomena affect somatic cells. If a replication mistake occurs in the formation of a germline cell (e.g., in gametes), the DNA alteration may be transmitted to that individual’s offspring .

22. Where can RNA be found within cells?

In the nucleus of eukaryotic cells, RNA can be found in the nuclear fluid along with DNA, and is also the main component of the nucleolus. In the cytosol (in eukaryotes or in bacteria), RNA molecules can be found on their own, as a structural component of ribosomes (organelles specialized in protein synthesis) or even bound to them਍uring the protein-making process. Mitochondria and chloroplasts also have their own DNA and RNA.

23. Do RNA molecules have two polynucleotide chains like DNA?

Only DNA has two polynucleotide chains. RNA contains only one polynucleotide chain.

DNA Transcription

24. What is the production of RNA called and what enzyme catalyzes this process?

The making of RNA from information contained in DNA is called transcription. The enzyme that catalyzes this process is RNA polymerase.

25. What are the similarities and the differences between the transcription process and the replication processes?

A DNA polynucleotide chain serves as a template in replication (DNA duplication) as well as in transcription (RNA formation). In both processes, the pairing of the two polynucleotide chains of the original DNA molecule is broken by the cutting of hydrogen bonds so that chains can be exposed as templates. The reaction is catalyzed by specific enzymes in both transcription and in replication.

In replication, the enzyme DNA polymerase catalyzes the formation of a new polynucleotide chain by using free nucleotides in the solution and inserting them into the new chain depending on the DNA template exposed and following the rule A-T, C-G. In transcription, the enzyme RNA polymerase makes a new polynucleotide chain depending on the DNA template exposed, and obeying the rule A-U, C-G.

In replication, the original template DNA chain is bound to the newly formed DNA chain via hydrogen bonds and a new DNA molecule is then created. In transcription, the bond between the template DNA chain and the newly formed RNA comes undone and RNA composed of only one polynucleotide chain is released.

Types of RNA

26. What are the three main types of RNA? What is heterogeneous RNA?

The three main types of RNA are: messenger RNA, or mRNA transfer RNA, or tRNA and ribosomal RNA, or rRNA.

The newly formed RNA molecule, a precursor to mRNA, is called heterogeneous RNA (hnRNA). Heterogeneous RNA contains areas called introns and exons. hnRNA is processed in many chemical steps, introns are removed and mRNA is created, formed only of exons, the biologically active nucleotide sequences.

The Different Functions of DNA and RNA

27. What is the difference between DNA and RNA with respect to their biological function?

DNA is the source of information for RNA production (transcription) and therefore for protein synthesis. DNA is still the basis of heredity, due to its replication capability.

Messenger RNA is the template for protein synthesis (translation). In this process, tRNA and rRNA are also involved, since the first carries amino acids used in the formation of the polypeptide chain and the second is a structural component of ribosomes (the organelles where proteins are made).

Reverse Transcription

28. Is there any situation in which DNA is made based on an RNA template? Which is the enzyme involved?

The process in which DNA is synthesized by using an RNA chain as a template is called reverse transcription. In cells infected by retroviruses (RNA viruses, like the AIDS or SARS viruses), reverse transcription occurs and DNA is made from information contained in viral RNA.

Viral RNA within the host cell produces DNA with the help of an enzyme called reverse transcriptase. Based on that DNA, the host cell then makes viral proteins, new viruses are assembled and viral replication occurs.

The Heterogeneity of Nucleic Acids

29. Do the phosphate and the pentose groups give homogeneity or heterogeneity to nucleic acid chains? What about the nitrogenous groups? Based on this, which of those groups is likely to directly participate in highly diverse and heterogeneous genetic coding, or rather, which of those groups is the basis of the information for protein production?

The phosphate and pentose groups are the same in every nucleotide that composes a nucleic acid. As result, they are the reason for the homogeneity of the molecule. However, nitrogenous bases can vary between adenine, thymine, cytosine and guanine (in DNA) and uracil (in RNA). These variations are the reason for the heterogeneity of the nucleic acid molecule.

Homogeneous portions of a molecule seldom store any information, for the same reason that a sequence of the same letter of the alphabet cannot make many words with different meanings. The nitrogenous bases, on the other hand, because they are different (four different types for RNA or DNA), can make the different sequences and combinations that allow for the diversity of the genetic code. 

Now that you have finished studying Nucleic Acids, these are your options:


Chemical Biology Lab Creating DNA-based Nanomachines that can Self Assemble

Professor Tao Ye and colleagues have received a $1.18 million grant from the Department of Energy to study how DNA molecules can arrange themselves into nanostructures that could form the basis of nanoelectronic circuits.

All living things are the products of self-assembly, a process in which proteins and other molecules arrange themselves into elaborate structures according to the “blueprint” encoded in DNA. Researchers in the field of DNA nanotechnology have discovered methods that allow DNA molecules to fold themselves into a variety of artificial nanostructures.

The Ye lab group, in the Department of Chemistry and Chemical Biology, is using these DNA nanostructures to develop biosensors with a wide range of applications in medicine. But the self-assembly process can also be used for non-biological applications by building larger structures that can feature prominently in energy harvesting and circuits for computers, among other areas.

Companies such as Intel use a process called lithography to create nanoscale transistors from semiconductors and to connect billions of these tiny transistors to create computer chips and microprocessors. But lithography is slow, takes many repetitions and is difficult to use to build smaller and smaller structures.

“Instead of relying on lithography, wouldn’t it be great if molecules and circuit components assembled themselves into devices? We want to learn from nature’s tricks to create highly complex and functional biological structures and repurpose self-assembly to create materials to convert energy or create complex circuits,” Ye explained.

These self-assembled DNA structures are a promising starting point. But, so far, many of the self-assembled structures are too defective and small for such applications. Ye and his students have used the atomic force microscope and other nanoscience tools to take snapshots of these self-assembling processes on solid supports to better understand how the molecules come together.

“The nanoscale arrangements of biomolecules, such as proteins and DNA, underlie a wide spectrum of biological functions,” Ye said. “But our ability to measure and control them is very limited.”

Over the next three years, working with their partners at Duke and Emory universities, Ye and his students will used advanced microscopy techniques to understand how the DNA nanostructures order themselves, why defects happen and how to overcome them.

They hope the experiments will lead to more predictive models on how these structures form. They also aim to create a way to allow the tiny structures to connect to each other so they can scale themselves up into specifically shaped, larger assemblies.

“We have the molecule to seed them for the larger shapes, we just need to understand the process,” Ye said. “We’re pushing the envelope here.”


3. If a DNA molecule has the message: I will insert a DNA sequence here , what would be the amino acids in the protein? What would happen if the DNA message changed to I will insert a different sequence with a base change? Be specific in your answer.

When DNA is replicated, you wind up with 2 DNA molecules. However, one strand of each of the new DNA molecules is the ORIGINAL DNA, and one strand is newly synthesized. The proof reader enzymes check the new copy against the original strand to make sure the bonding rules are followed.


Out of all the information covering mitosis and meiosis, you may want to consider the following questions to help prepare you for an upcoming mitosis quiz. Choose to break down the information as you see fit and in a language, you can understand. Again, drawing images to help you better conceptualize the process is helpful, as well as using correct terminology.

Which Structure Is Responsible For Moving Chromosomes During Mitosis?

The centromere is a region of DNA that holds together the two chromatids of a duplicated chromosome. Centromeres are responsible for attaching microtubules and direct the movement of chromosomes in both the process of mitosis and meiosis.

First, the chromosomes move toward the center of a cell during metaphase, and then they proceed to opposite directions during anaphase.

Why Do Chromosomes Fail To Separate Within Mitosis?

Nondisjunction is when a pair of homologous chromosomes fail to separate. There are three forms of nondisjunction, and two happen during the process of meiosis I and meiosis II.

When the sister chromatids fail to separate during the process of mitosis, the number of chromosomes is abnormal, resulting in aneuploidy.

If a single chromosome is lost from a diploid genome, it is called monosomy. If a chromosome is gained, it is called a trisomy.

When chromosomes fail to separate correctly, it can lead to a genetic disorder such as Downs Syndrome or Turner Syndrome. In the most extreme cases, aneuploidy can be lethal. The risk of nondisjunction taking place increases exponentially with the rising age of parent cells.

Typically disjunction is found during the process of meiosis.

At Which Phase Do Chromosomes Become Visible And Of What Do Chromosomes Consist?

Before chromosomes become visible during the prophase stage, the chromosomes are long strands called chromatin. The chromatin is tightly wound up into chromosomes.

Chromosomes are made up of DNA which is coiled tightly around histones. Histones are proteins which support the structure of the thread-like structures. Chromosomes are not visible under a microscope if the cell is not dividing, and it is not visible in the nucleus of the cell.

The short arm of a chromosome is the ‘p arm,' and the long arm is known as the ‘q arm.'

What Is Cytokinesis?

Cytokinesis is the process when cells physically divide. The cytoplasm of a parent cell splits into two daughter cells. This process starts during anaphase and doesn't stop until the telophase. Cytokinesis takes places during both mitosis and meiosis.

When and Why Will Cells Divide, How Many Chromosomes Will They Have, And What Triggers This Process?

Cellular division during mitosis may be triggered because of the need to replace or repair dead or lost cells or to grow in size. As part of the cell cycle, a cell will prepare to divide at interphase and begins its division process during mitosis.

A single cell will divide and reproduce copies of its DNA into two identical cells. The number of chromosomes will be the same as in the parent cell.

What Is The Difference Between A Diploid And A Haploid?

Diploid cells have a set of chromosomes from two different parents, with two homologous copies of each chromosome of their parents. Diploid cells reproduce by mitosis, and somatic cells are examples of diploid cells.

Haploid cells are created because of the meiosis process. Gametes or sex cells are a common type of haploid cells. Haploid cells only have one complete set of chromosomes.

Define Polyploidy And Aneuploidy?

When there is a variation in the number of chromosomes, it is described as being either aneuploidy, monoploidy, or euploidy. Depending on whether one part of a chromosome is lost, an entire set of chromosomes is lost, or one or more than one complete set of chromosomes is gained the term changes.

With chromosomes, conditions can either be double monosomic or double tetrasomic.

What Is An Allele And The Law Of Independent Assortment?

A gene is a single unit of information that is hereditary. Except in the case of some viruses, genes are made up of DNA which transmits traits. An allele is a genetic sequence which is a variant of a gene. When there are differences among copies of a gene, they are called alleles. At the locus of a gene, there are only two alleles present.

Gregor Mendel has been credited with our enlightened understanding about genetics, heredity, and what happens when there are variants in genetic transmission. According to Mendel's Law of Independent Assortment, a pair of alleles will separate independently when gametes are forming. Traits are transmitted to offspring independently.

The Law of Independent Assortment was formed on principles uncovered when Gregor Mendel conducted experiments creating dihybrid crosses between plants which had two different traits. As a result of Mendel's experiments, a ratio developed to reinforce this concept.

What Type Of DNA Damage Occurs When Cytokinesis And Mitosis Fail?

If a cell fails to separate during cytokinesis, it may have multiple nuclei.

During the prometaphase and metaphase stage, if a cell fails, it enters the G1 phase of a cell cycle, or it results in cell death. The checkpoints within the cell cycle help to regulate the process of cell division and will signal to different pathways if there is a failure.

Steps are automatically taken to prevent any damaged DNA from being reproduced or transmitted to a new generation of cells, to protect integrity.

When mitosis fails to carry out is process an abnormal number of chromosomes is created. To prevent continuous cell division, abnormal cells may be removed. A failure in mitosis typically activates cell death and consequent DNA damage.


Learn about Genetic Engineering through a Few Questions and Answers

Biotechnology is the application of biological knowledge to obtain new techniques, materials and compounds for pharmaceutical, medical, agricultural, industrial and scientific use, that is, for practical use.

The first fields of biotechnology were agriculture and the food industry. Nowadays, many other practical fields use its techniques.

Genetic Engineering Definition

More Bite-Sized Q&As Below

2. What is genetic engineering?

Genetic engineering is the use of genetic knowledge to artificially manipulate genes. It is one of the fields of biotechnology.

3. At the present level of advancement of biotechnology, what are the main techniques of genetic engineering?

The main genetic engineering techniques used today are: recombinant DNA technology (also called genetic engineering), in which pieces of genes from an organism are inserted into the genetic material of another organism to produce recombinant organisms nucleus transplantation technology, popularly known as “cloning”, in which the nucleus of a cell is grafted into an enucleated egg cell of the same species to create a genetic copy of the donor (of the nucleus) individual and DNA amplification technology, or PCR (polymerase chain reaction), which allows to produce millions of replications of the chosen fragments of a DNA molecule.

Recombinant DNA technology is used to create transgenic organisms, such as mutant insulin-producing bacteria. Nucleus transplantation technology is in its initial development but is the basis, for example, of the creation of “Dolly” the sheep. PCR has numerous practical uses, such as in medical tests to detect microorganisms present in blood and tissues, DNA fingerprinting and the obtainment of DNA samples for research.

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Restriction Enzymes and Recombinant਍NA Technology

4. What are restriction enzymes? How do these enzymes participate in recombinant DNA technology?

Restriction enzymes, or restriction endonucleases, are enzymes specialized in the cutting of DNA fragments, which each have an effect on specific sites of the DNA molecule. Restriction enzymes are used in recombinant DNA technology to obtain with pieces of DNA molecules with precision, which will later be inserted into other DNA molecules cut by the same enzymes.

5. What are DNA ligases? How do these enzymes participate in recombinant DNA technology?

DNA ligases are enzymes specialized in tying the complementary DNA chains that form the DNA double helix. These enzymes are used in recombinant DNA technology to insert pieces of DNA cut by restriction enzymes into other DNA molecules undergoing the effect of the same endonucleases.

6. What are plasmids?

Plasmids are circular DNA molecules present in the genetic material of some bacteria. They may contain the genes responsible for bacterial resistance to some antibiotics as well as the genes for producing proteins that cause virulence (pathogenic hostility). 

7. How is genetic engineering used to create bacteria capable of producing human insulin?

In the production of human insulin by bacteria, the human insulin gene is incorporated into the genetic material of these microorganisms. The mutant bacteria multiply, forming lineages of insulin-producing bacteria.

Bacteria contain circular strands of DNA called plasmids, which are mini-chromosomes that act as an accessory to the primary DNA. To create mutant bacteria capable of producing insulin, a plasmid is submitted to the effect of restriction enzymes (restriction endonucleases) specialized in cutting DNA fragments. The once circular plasmid is opened by the restriction enzyme. The same enzyme is used to cut a human DNA molecule containing the insulin gene. The piece of human DNA containing the insulin gene is then bound to the plasmid at its ends through the help of DNA ligases. The recombinant plasmid containing the human insulin gene is then inserted into the bacteria.

Another human hormone already produced by recombinant bacteria is GH (somatotropin, or growth hormone).

The insertion of DNA molecules into the cells of an individual is also used in gene therapy, a promising treatment for genetic diseases. In gene therapy, cells from an organism deficient in the production of a given protein receive (by means of vectors, such as virus) pieces of DNA containing the protein gene and then begin to synthesize the protein.

Genetic Cloning

8. What is cloning?

Cloning is the production of an organism genetically identical to another by means of genetic engineering.

The basis of cloning is nucleus transplantation technology. A nucleus from a cell is extracted, generally from an embryonic (undifferentiated) cell and this nucleus is inserted into a previously enucleated reproductive cell (in general an egg cell) the egg is then implanted in the organ where the embryonic development will take place. If embryonic development occurs, the new organism will have an identical genetic content to the organism organism whose cell nucleus was used in the transplantation.

Polymerase Chain Reaction

9. What is PCR? How does PCR works?

PCR, polymerase chain reaction, is a method to synthesize many copies of specific regions of a DNA molecule known as target-regions. Its inventor, Kary Mullis, won the Nobel Prize for Chemistry in 1993.

First, the DNA to be tested is heated to cause the double helix to rupture and the polynucleotide chains to be exposed. Then, small synthetic sequences of DNA known as primers and containing nucleotide sequences similar to the sequences of the extremities of the region to be studied (for example, a region containing a known gene exclusive to a given organism) are added. The primers are paired with the original DNA at the ends of the gene to be amplified. Enzymes known as polymerases, which catalyze DNA replication, and nucleotide supply are added. The primers are then completed and the chosen region is replicated. In the presence of more primers and more nucleotides, millions of copies of that specific region are generated. (PCR is very sensitive, even when using a minimal amount of DNA).

DNA Fingerprinting

10. What molecular biology principle is the basis for DNA fingerprinting?

DNA fingerprinting, the method of the identification of individuals using DNA, is based on the fact that the DNA of every individual (except for identical twins and individual clones) contains nucleotide sequences exclusive to each individual.

Although normal individuals of the same species have the same genes in their chromosomes, each individual has different alleles and even in the inactive portions of the chromosomes (heterochromatin), there are differences in nucleotide sequences among individuals.

Genetic Engineering Dangers and Ethics

11. Why are recombinant DNA technology and nucleus transplantation technology still dangerous?

Recombinant DNA technology and nucleus transplantation technology (cloning) are extremely dangerous since they are able to modify, in a very short time, the ecological balance that evolution has taken millions of years to create on the planet. During the evolutionary process, under the slow and gradual effect of mutations, genetic recombinations and natural selection, species emerged, were modified, and genetic heritages were formed. With genetic engineering, however, humans can mix and modify genes, making changes with unpredictable long-term consequences, risking the creation of new plant or animal diseases, new types of cancers and new disease outbreaks. It is a field as potentially dangerous as the manipulation of nuclear energy.

12. What is the main moral problem regarding the cloning of human individuals?

In addition to the biological perils, a very serious moral problem involves nucleus transplantation technology concerning humans: the individual rights of a human being are violated when a man or woman is made as a copy of another.

Since it is impossible to first ask if the person to be cloned wants to be a genetic copy of another person or not, it is clear that the most important human right is being violated when making one human as a copy of another: the right to individual freedom. This is a danger to democracy, whose most basic principle is the respect of individual freedom.

Now that you have finished studying Genetic Engineering, these are your options:


Did you know that more than 26 million Americans have had a personal genomics test performed? And within the next two years, the number is expected to grow rapidly.

As genomic testing becomes more common, you might wonder what the implications are for your future. Perhaps you’ve had a genetic test performed or plan to do one soon. What should you expect? And what should you be cautious about?

Here are some tips when considering a DNA profile:

  • Talk to your family first—this may help plan for any potential surprises
  • Keep an open mind—your results may not be conclusive or may change in time as databases grow
  • Manage your expectations—the results might not be what you expect, but that doesn’t have to change your identity or story

“We need to start having a set of public conversations about all of the different areas of genetic profiles in our lives,” said Professor Graham Coop, Department of Evolution and Ecology, “because the applications of these methods are going to evolve very quickly.”

Coop works to demystify the evolutionary forces that shape genetic differences between individuals, populations and closely related species. Coop, a member of the UC Davis Center for Population Biology, has provided popular commentary on the methods underlying DNA profiles and the and ethical questions that they raise.

What’s in a profile?

One thing Coop stresses is that these tests don’t look at your entire genome. Instead, they look at a set of about a million locations known to vary between individuals. These data are analyzed in a range of ways.

The services that genetic profiling companies offer fall into three major categories: medical traits, genetic lineages (your genetic origin story) and close genetic matches (your family tree). These different categories of the tests vary a lot in their certainty and relevance in ways that won’t always be obvious to consumers.

The medical trait tests offered by these companies are regarded as the least reliable because they’re often based on weak predictions. And since 80 to 90% of genetic databases are people of European descent-specific, the information often isn’t likely to be helpful to those outside these groups. However, some genetic variants involved in Alzheimer’s and Parkinson’s diseases, as well as some of those involved in BRCA1 and BRCA2 cancers, can be ID’ed.

You should be aware that you could learn something serious from these tests, and you should talk to your doctor if that happens. Coop sees the capabilities of these medical databases improving in the years to come, but for now, they are not the primary driver of the genetic profile boom.

A more popular aspect of these tests that provide background about your ancestry. These can also sometimes be misleading or inconclusive for many reasons, especially for people with non-European ancestry. But the largest driver of growth for these companies is consumers’ interest in identifying direct family relationships.

Curious about how genetics affects your daily life?

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The future of how personal genomics will shape our lives is being written today. It's time for a discussion. UC Davis/Getty Images

Thy profile and thee

As a nation of immigrants, we are a melting pot more fragmented than other parts of the world. Americans have often disconnected from their family roots—by choice or by force—and seek ways to reconnect to their broad families and homes.

“If I compared my genome with your genome, roughly only one in a thousand base pairs would differ between our genomes,” said Coop. This holds true among populations, the most genetic differences between humans are amongst individuals from similar populations and groups, rather than individuals from different populations and groups. For example, Coop’s genome is very similar to people from all around the world, but the test identified him as European as he’s slightly more related to people from Europe because his ancestors were European. However, because these companies provide seemingly precise, quantitative answers—you are 50% European, you are 25% East Asian, etc.,—these blanket statements give the impression that ethnicity is genetic. Immediately, a very discrete term is brought to life as soon as you read the words.

Using Genomics to Trace Human Family Origins with Undergraduate of the Year Cole Williams

2019 Undergraduate of the Year Cole Williams studies the genetics of African hunter-gatherer and pastoralist groups. He designed an algorithm capable of handling diverse populations, technical artifacts and complex family genealogies that runs rapidly on human genomic datasets.

“How you choose to identify and how society identifies you is complicated, right?” said Coop. “It's based on who your parents are and where you grew up. It’s based on lots of different things. Very little of that is actually based on genetics.”

Keeping it (all in perspective) in the family

Sometimes test results will run contrary to family history or identity. Time and time again, Coop’s seen how shocking it can be for people when their genetic tests don’t lineup with what they expected.

“You might think that it’s telling you something important about who you are, right?” Coop said. “These tests can be an incredibly useful tool for learning about family history. But it's only a small aspect of who you are and who your family is, and it may have little to do with how you identify.”

In some cases, DNA profiles unearth critical information, such as unknown half-siblings or that a parent is not an actual biological parent. Taking the time to talk with your family before taking a test or reviewing your results can help mitigate any earth-shattering surprises.

“You should ask yourself, are you ready for that kind of information?” said Coop. “For instance, before I got mine done, I talked to my parents. I said, ‘is there anything that you want to tell me first? It’ll be okay if you to tell me not to do it.’”

Hobbyist DNA Services May Be Open to Genetic Hacking

Professor Graham Coop and postdoctoral researcher Michael “Doc” Edge, both of the Department of Evolution and Ecology, warn that “direct to consumer” DNA testing services could be vulnerable to a sort of genetic hacking.

Privacy and protecting yourself

The popularity of personal genomics raises a host of issues about privacy. You can learn something new about your family history from these tests, but you are sharing your DNA with a personal genomics company. New applications will further accelerate the way this data is used, largely in ways we can’t yet anticipate or imagine. There are some protections in place. The Genetic Information Nondiscrimination Act of 2008 was established to protect Americans from genetic-based discrimination in health insurance and employment. Proponents of GINA, as it is known, see this as vital protection and are concerned that any forthcoming changes to this federal legislation would erode individual privacy.

Fortunately, California has an extended version called CalGINA, which broadens protections from medical treatment and employers and housing to business services and public education. But these protections aren’t in place everywhere.

One of the more surprising recent applications of personal genomics is their use by law enforcement. The most popular case involving DNA familial databases for crimefighting came in the apprehension of the suspected Golden State Killer, Joseph James DeAngelo, based on the analysis of a DNA sample carefully preserved from a crime scene kit decades ago. Led by UC Davis alumnus Paul Holes (’90 B.S., Biochemistry), investigators uploaded the genetic profile to the public database GEDmatch and began the tedious process of working backward through DeAngelo’s family tree to find him. After an extensive but uncertain search, investigators collected a DNA sample from DeAngelo’s car door. That sample was a genetic match to the crime scene sample.

In 2018, a Science study predicted that within a year or two, the DNA of 90% of Americans of European descent will be identifiable in this manner, even if they have never had a personal genomics test. The question of how these searches can and should be used by law enforcement is one that ethicists and legal experts at UC Davis and beyond are struggling to answer. (read “Want to See My Genes? Get a Warrant,” a New York Times op-ed by Elizabeth Joh, a professor of law).

Navigating the ethics of a brave new world

Popular support to solve violent crimes like serial murder is overwhelming. According to Coop, the Golden State Killer case has led to a range of other applications by law enforcement and raises debate over which level of crime is appropriate for these genetic genealogy searches. Coop notes that law enforcement is already exploring applications into other types of crimes. In some cold-case infant deaths, the abandoned babies were linked genetically to their parents via public databases. The parents were tracked down and arrested. It’s a complicated ethical scenario.

“You can also see how quickly and slippery the slope may be from identifying murderers to identifying an aborted fetus using these techniques,” warns Coop.

Pinning down the circumstances under which genetic genealogy searches are used will be vital in setting the legal precedents that will impact millions of Americans. The DOJ issued a new provisional set of guidelines that go into effect Nov. 1.

As the technological capacity of genetic profiling continues to outpace legislation, Americans are taking notice of the need to recognize genetic privacy as a fundamental right. The surge in consumer DNA profiling highlights the eternal political balancing act of privacy versus security, but at an unprecedented biological level.

The future of personal genomics is by no means written. Like most technologies, it carries the potential for both positive and negative applications. It will take concerted efforts to raise public awareness about how the information we get from these tests will inform our individual and collective identities and privacies. The time to start the discussion is now.


Watch the video: DNA MCQs: Biochemistry MCQs: Molecular basis of Inheritence (January 2023).