Question 1

Which of the following statements about lac-operon is correct ?

Accepted Answer

The i gene in the lac operon codes for the repressor protein. It is a regulatory gene that is constitutively expressed, meaning it is transcribed continuously to maintain a basal level of repressor in the cell. Galactose does not act as an inducer of the lac operon; lactose or allolactose serves as the inducer. Lactose binds to the repressor protein and inactivates it, preventing it from binding to the operator region. Genes z, y, and a are structural genes that share a single common promoter, w

Question 2

Which of the following enzymes synthesizes precursor mRNA ?

Accepted Answer

In eukaryotes, there are three major types of RNA polymerases: RNA polymerase I transcribes rRNAs (28S, 18S, and 5.8S). RNA polymerase II transcribes the precursor of mRNA, which is known as heterogeneous nuclear RNA (hnRNA). RNA polymerase III is responsible for the transcription of tRNA, 5S rRNA, and snRNAs. Therefore, RNA polymerase II synthesizes precursor mRNA. Answer: RNA polymerase II

Question 3

Which of the following statements are correct with reference to a transcription unit ? A. A transcription unit in DNA is defined primarily by three regions : promoter, structural gene and terminator.

Accepted Answer

Statement A is correct as a transcription unit in DNA is primarily defined by three regions: a promoter, a structural gene, and a terminator. Statement B is correct because the promoter is located towards the 5'-end (upstream) of the structural gene, with reference to the polarity of the coding strand. Statement C is correct as the promoter is a specific DNA sequence that provides a binding site for RNA polymerase to initiate transcription. Statement D is correct because the presence and positio

Question 4

Which of the following statements are correct with reference to packaging of DNA helix ? A. Histones are organized to form a unit of eight molecules called histone octamer. B. Histones are negatively

Accepted Answer

Statement A is correct. Histones are organized to form a unit of eight molecules called a histone octamer. Statement B is incorrect. Histones are positively charged, basic proteins, not negatively charged. Statement C is correct. Histones are rich in the basic amino acid residues lysine and arginine, which carry positive charges in their side chains. Statement D is incorrect. DNA is a negatively charged molecule (due to phosphate groups), which is wrapped around the positively charged histone oc

Question 5

Arrange the following steps of DNA fingerprinting in a correct sequence. A. Isolation of DNA and its digestion by restriction endonucleases. B. Hybridisation using a labelled VNTR probe. C. Transferri

Accepted Answer

The technique of DNA fingerprinting involves the following steps in sequence: 1. Isolation of DNA and its digestion by restriction endonucleases (A). 2. Separation of the digested DNA fragments by gel electrophoresis (E). 3. Transferring (blotting) of the separated DNA fragments to synthetic membranes, such as nitrocellulose or nylon (C). 4. Hybridisation using a radiolabelled VNTR probe (B). 5. Detection of the hybridised DNA fragments by autoradiography (D). The correct sequence is A, E, C, B,

Question 6

In the lac operon, the z gene codes for :

Accepted Answer

In the lac operon, the structural genes are z, y, and a. The z gene codes for beta-galactosidase, which is primarily responsible for the hydrolysis of the disaccharide lactose into its monomeric units, galactose and glucose. The y gene codes for permease, which increases permeability of the cell to beta-galactosides. The a gene codes for a transacetylase. The i gene codes for the repressor of the lac operon. Answer: beta-galactosidase

Question 7

Given below are two statements : Statement I : In the RNA world, RNA is considered the first genetic material evolved to carry out essential life processes. RNA acts as a genetic material and also as

Accepted Answer

In RNA world, RNA was the first genetic material as there are enough evidences to suggest that essential life processes (such as metabolism, translation, splicing, etc) evolved around RNA. RNA used to act as a genetic material as well as catalyst (there are some important biochemical reaction in living systems that are catalysed by RNA catalysts not by protein enzymes) so, statement I is correct statement II is also correct as DNA being double stranded and having complementary strands further re

Question 8

Match List I with List II: array |l|l|l|l| & List - I & & List - II \ A . & Alfred Hershey and Martha Chase & (i) & Streptococcus pneumoniae \ B. & Euchromatin & (ii) & Densely packed and dark-stain

Accepted Answer

The unequivocal proof that DNA is the genetic material came from the experiment of Alfred Hershey and Martha Chase. Euchromatin are lightly stained region with loosely packed chromatin fibre. Frederick Griffith performed series of experiments by selecting the different strains of Streptococcus pneumoniae. Heterochromatin are darkly stained region with tightly packed chromatin fibre.

Question 9

Which of the following are the post-transcriptional events in an eukaryotic cell? A. Transport of pre-mRNA to cytoplasm prior to splicing. B. Removal of introns and joining of exons. C. Addition of me

Accepted Answer

The process of copying genetic information from one strand of the DNA into RNA is known as transcription. It occurs in the cytoplasm with the help of transcripting enzyme. Transport of pre-mRNA to cytoplasm prior to splicing is a part of transcription. The primary transcript is converted into functional mRNA after post transcriptional processing involves 3 steps as follows- - Modification of 5' end by capping, - Tailing, - Splicing. Base pairing of two complementary RNA is not on event of post-t

Question 10

Which factor is important for termination of transcription?

Accepted Answer

In prokaryotes the RNA polymerase is only capable of catalysing the process of elongation. It associates transiently with initiation factor ( ) and termination factor ( ) to initiate and terminate the transcription respectively.

Question 11

Histones are enriched with -

Accepted Answer

In eukaryotes, packaging of DNA is much more complex. There is a set of positively charged, basic proteins called histones. Histones are organised to form a unit of light molecules called histone octamer. They are rich in the basic amino acid residues lysine and arginine.

Question 12

Which chromosome in the human genome has the highest number of genes?

Accepted Answer

In human genome, Chromosome 1 has the highest number of genes, i.e., 2968.

Question 13

Who proposed that the genetic code for amino acids should be made up of three nucleotides?

Accepted Answer

George Gamow, a physicist proposed that genetic code for amino acids should be made up of three nucleotides.

Molecular Basis of Inheritance — Previous Year Questions & Solutions