Chapter 6: Molecular Basis of Inheritance

Q1Written answer

What is the function of histones in DNA packaging?

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Ans: Histones are a type of protein that is extremely alkaline. The nucleus of eukaryotic cells contains them. Histones wrap and organize DNA into nucleosomes, which are structural units. They function as spools around which DNA is wound, allowing a lengthy strand of DNA to fit into a much smaller space. As a result, a.1.8m strand of DNA is spooled to form a structure that is only 90 microns in size.

Q2Written answer

Distinguish between heterochromatin and euchromatin. Which of the two is transcriptionally active?

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Ans: Differences between heterochromatin and euchromatin are:

Heterochromatin	Euchromatin
They are darkly staining and are dispersed or gathered near the nuclear envelope.	Euchromatin is not willingly stainable and is dispersed.
These are transcriptionally less active or sedentary.	These are transcriptionally energetic.

Q3Written answer

The enzyme DNA polymerase in E. coli is a DNA-dependent polymerase and also has the ability to proofread the DNA strand being synthesized. Explain. Discuss the dual polymerase.

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Ans: DNA polymerase is dubbed DNA – dependent because it catalyzes the polymerization of deoxynucleotides using a DNA template. When a fresh strand of DNA is digested, this enzyme advances forward to speed up the polymerization process. It also "proofreads" the strand as it is being created. It helps to speed up the process by doing so. As a result, it has a dual nature, in that it reads the template before proofreading the new strand.

Q4Written answer

What is the cause of the discontinuous synthesis of DNA on one of the parental strands of DNA? What happens to these short stretches of synthesized DNA?

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Ans: Only one mode of polymerization is catalyzed by DNA polymerase, namely 5' – 3'. As a result, replication occurs continuously on one strand (3'-5'), but not on the other (5'– 3'). DNA ligase is used to unite the fragments that are not connected.

Q5Written answer

Given below is the sequence of the coding strand of DNA in a transcription unit 3’-AATGCACTATTAGG–5’

Write the sequence of:

(a) its complementary strand

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Ans: 5’–TTACGTCGATAACC–3’

(b) the mRNA

Ans: 5’–UUACGUCGAUAACC–3’

Q6Written answer

What is DNA polymorphism? Why is it important to study it?

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Ans: DNA polymorphism occurs when an inheritable mutation emerges in a population at a high frequency. Because inheritable mutations eventually contribute to evolution, studying DNA polymorphism is crucial from an evolutionary standpoint.

Q7Written answer

Based on your understanding of genetic code, explain the formation of any abnormal hemoglobin molecule. What are the known consequences of such a change?

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Ans: HbA, HbA2, and HbF are the three kinds of hemoglobin found in humAns: The HbS type of hemoglobin is formed when the genes for the beta chain on hemoglobin are altered. Sickle cell anemia is caused by this kind of hemoglobin molecule.

Q8Written answer

Sometimes cattle or even human beings give birth to their young ones that are having extremely different sets of organs like limbs/position of the eye(s) etc. Comment.

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Ans: The presence of several organs in an animal is caused by a disruption in the coordinated regulation of gene expression.

Q9Written answer

In a nucleus, the number of ribonucleotide triphosphates is 10 times the number of deoxyribonucleotide triphosphates, but only deoxyribonucleotides are added during the DNA replication. Suggest a mechanism.

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Ans: Only deoxyribonucleoside triphosphates are recognized by DNA polymerase, which is highly specific. As a result, it is unable to retain RNA nucleotides.

Q10Written answer

Name a few enzymes involved in DNA replication other than DNA polymerase and ligase. Name the key functions for each of them.

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Ans: Other enzymes and their primary roles are listed below:

(a) Primase is a protein that attaches RNA primers to template strands. The RNA primer is removed by RNAse.

(b) Exonuclease: Starts nucleotide cleavage one at a time.

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