17 Most VSAQ’s of Molecular Basis of Inheritance Chapter in Inter 2nd Year Botany (TS/AP)

2 Marks

VSAQ-1 : Distinguish between heterochromatin and euchromatin. Which of the two is transcriptionally active?

  1. Heterochromatin:
    • Densely packed and appears dark under a microscope.
    • Transcriptionally inactive, meaning genes within heterochromatin are typically not actively transcribed or expressed.
  2. Euchromatin:
    • Loosely packed and appears light under a microscope.
    • Transcriptionally active, indicating that genes within euchromatin are actively transcribed and can be expressed to carry out cellular functions.

VSAQ-2 : Who proved that DNA is genetic material? What is the organism they worked on?

Alfred Hershey and Martha Chase provided evidence demonstrating that DNA serves as the genetic material. Their groundbreaking experiments were conducted with bacteriophages, which are viruses that infect bacteria. These experiments played a pivotal role in establishing DNA as the primary carrier of genetic information in living organisms.

VSAQ-3 : What is the function of DNA polymerase?

The primary function of DNA polymerase is to catalyze the polymerization of a vast number of nucleotides into a growing DNA strand during replication and repair processes. Additionally, DNA polymerase is known for catalyzing these reactions with a high degree of accuracy, ensuring that the newly synthesized DNA strand matches the original template strand with exceptional fidelity. This precision in nucleotide incorporation is vital for maintaining the integrity and accuracy of the genetic information encoded in DNA.

VSAQ-4 : What are the components of a nucleotide?

  1. Nitrogenous base: This includes adenine (A), thymine (T), cytosine (C), guanine (G), or uracil (U) in the case of RNA.
  2. Pentose sugar: It can be either ribose (in RNA) or deoxyribose (in DNA).
  3. Phosphate molecule: One or more phosphate groups are attached to the sugar, forming the backbone of the nucleotide and providing the necessary energy for DNA and RNA synthesis and function.

VSAQ-5 : Given below is the sequence of coding strand of DNA in a transcription unit. 5 ‘ A  A T G C T A T T A G G – 3’ write the sequence of a. Its complementary strand b. The mRNA..

  1. Complementary Strand (opposite DNA strand): 3′ – T T A C G T C G A T A A T C C – 5′
  2. mRNA (transcribed from the coding strand, with thymine replaced by uracil in RNA): 3′ – U U A C G U C G A U A A U C C – 5′

VSAQ-6 : Name any three viruses which have RNA as the genetic material.

Three Viruses with RNA as Genetic Material:

  1. Influenza virus
  2. Polio virus
  3. HIV (Human Immunodeficiency Virus)

VSAQ-7 : What are the components of a transcription unit?

A transcription unit consists of three key components: a promoter, which marks the start of transcription and binds RNA polymerase; the structural gene, containing the genetic information to be transcribed; and a terminator, indicating the end of transcription and signaling RNA polymerase to cease synthesis. These elements collectively govern the process of gene transcription.

VSAQ-8 : What is the difference between exons and introns?

Exons are coding sequences within a gene that are retained and expressed in the final, mature RNA. They contain the genetic information necessary to produce proteins or functional RNA molecules.

Introns, on the other hand, are non-coding sequences within a gene that are removed during the RNA processing or splicing process and do not appear in the mature RNA molecule. They do not contribute directly to protein or functional RNA synthesis.

VSAQ-9 : What is meant by capping and tailing?

Capping and Tailing Definitions:

  1. Capping is the process of adding a methyl guanosine triphosphate (m7G) cap to the 5′-end of hnRNA (pre-mRNA) during RNA processing. This modification plays a role in mRNA stability, processing, and translation initiation.
  2. Tailing, specifically polyadenylation, involves the addition of adenylate (A) residues to the 3′-end of an RNA molecule. This poly(A) tail is crucial for mRNA stability, export from the nucleus, and proper translation initiation.

VSAQ-10 : What is meant by point mutation? Given an example.

An illustrative example of a point mutation is the mutation in the hemoglobin gene responsible for sickle cell anemia. In this genetic disorder, a single nucleotide change leads to the substitution of glutamic acid with valine in the hemoglobin protein, resulting in the production of abnormal hemoglobin molecules and causing the characteristic sickle-shaped red blood cells.

VSAQ-11 : What is meant by charging of tRNA?

Charging of tRNA is the biochemical process that involves the attachment of the suitable amino acid to its corresponding transfer RNA (tRNA) molecule. This critical process is mediated by specific enzymes called aminoacyl-tRNA synthetases, and it necessitates the expenditure of energy in the form of adenosine triphosphate (ATP). Each tRNA molecule is linked to a particular amino acid, and the charging of tRNA guarantees the precise delivery of the correct amino acid to the ribosome during protein synthesis, ensuring the accuracy of the translation process.

VSAQ-12 : What is the function of the codon-AUG.

The codon “AUG” has a dual function in mRNA. Firstly, it serves as the initiation codon, marking the start of protein synthesis during translation. Secondly, it codes for the amino acid methionine, which is usually the first amino acid in the polypeptide chain of a protein. Thus, AUG plays a critical role in both initiating protein synthesis and specifying the initial amino acid in the protein’s sequence.

VSAQ-13 : Define stop codon. Write the codons.

A stop codon is a three-letter sequence in mRNA that signifies the termination of protein synthesis during translation. The three stop codons are UAA, UAG, and UGA. When encountered by a ribosome, these codons prompt the cessation of protein synthesis and the release of the newly formed polypeptide chain. Unlike regular codons that specify amino acids, stop codons do not code for any amino acid. Their pivotal role is to ensure the precise termination of protein synthesis.

VSAQ-14 : Write any two differences between DNA and RNA.

DNA vs. RNA – Two Key Differences

  1. Sugar Composition:
    • DNA utilizes deoxyribose sugar in its structure.
    • RNA incorporates ribose sugar in its backbone.
  2. Self-Replication Capability:
    • DNA possesses the ability for self-replication during cell division, ensuring the accurate duplication of genetic material.
    • RNA does not have the inherent capacity for self-replication and is not involved in DNA replication processes.

VSAQ-15 : In a typical DNA molecule, the proportion of Thymine is 30% of the N bases. Find out the percentages of other N bases.

The percentages of the N bases in a typical DNA molecule are as follows:

  1. Adenine (A): 30%
  2. Thymine (T): 30%
  3. Guanine (G): 40%
  4. Cytosine (C): 30%

These percentages are based on the complementary base-pairing rules in DNA, where A pairs with T, and G pairs with C.

VSAQ-16 : The proportion of nucleotides in a given nucleic acid are: Adenine 18%, Guanine 30%, Cytosine 42%, and Uracil 10%. Name the nucleic acid and mention the number of strands in it.

The nucleic acid with the given proportions of Adenine (18%), Guanine (30%), Cytosine (42%), and Uracil (10%) is RNA (Ribonucleic acid). RNA is typically single-stranded.

VSAQ-17 : What is the difference between the template strand and a coding strand in a DNA molecule?

Template Strand vs. Coding Strand – Differences

  1. Template Strand:
    • One of the two DNA strands.
    • Serves as the template for mRNA synthesis during transcription.
    • mRNA is synthesized through complementary base-pairing with the template strand.
    • Provides the sequence guide for mRNA formation.
  2. Coding Strand:
    • The complementary strand to the template strand in DNA.
    • Not directly involved in mRNA synthesis during transcription.
    • Has the same sequence as mRNA (except T/U substitution) and is often referred to as the sense strand due to its direct relation to the protein’s amino acid sequence.