Botany MCQs for NEET — Practice Questions with Answers

When error occurs at DNA replication stage, it will further affect the process of transcription i.e. formation of mRNA and translation i.e. synthesis of protein. This is because DNA molecule serves as the precursor in transcription and if an error gets incorporated in it, it will be carried further.

The above mentions sites and genes belong to lac operon.

1. Operator site: Repressor binding
2. Promoter site: RNA polymerase binding
3. Structural gene: codes proteins of enzymes
4. Regulator gene: codes repressor molecules

(page-117)

1. Termination: GTP dependent release factor recognises stop codon in translation and terminates the process of translation.
2. Translation: Aminoacyl tRNA synthetase are enzymes that catalyse aminoacylation reaction by linking an amino acid to its cognate tRNA in translation.
3. Transcription: Process of transcription is mediated (exonuclease activity) by RNA Polymerase in prokaryotes and RNA Polymerase I, II and III in eukaryotes.
4. DNA replication: During semiconservative DNA replication, leading strand is continuous strand whereas lagging strand is discontinuous and is composed of Okazaki fragments.

1. In 1953, James Watson and Francis Crick, based on the X-ray diffraction data produced by Maurice Wilkins and Rosalind Franklin combined with Chargaff's realization that A = T and C = G, proposed a very simple but famous Double Helix model for the structure of DNA.
2. Griffith based on his experiments concluded that there is some genetic material which is transferred from one generation to another.
3. Hershey-Chase experiment confirmed that proteins did not enter the bacteria from the viruses. DNA is therefore the genetic material that is passed from virus to bacteria

In dsDNA, A = T and G = C

A + T / G + C = 0.3

2A/2G = 0.3

A = 0.3 X G ----(i)

Also, (A + T) + (G + C) = 100 ---(ii)

Substituting all amino acids in terms of G :-

0.3G + 0.3G + G + G = 100

2.6G = 100

G = 38.5 = C

From (i)

A = T = 0.3G = 11.55

A + G / T + C = 11.55 + 38.5 / 38.5 + 11.55 = 1

RNA polymerase is the main enzyme for RNA synthesis in transcription.

The key differences between mRNA and tRNA are: B) tRNA has a more elaborated 3D structure due to extensive base pairing, and C) tRNA is smaller than mRNA. mRNA does not bear an anticodon, and tRNA has anticodons, not codons. Therefore, the correct option is o3.

Gene expression results in the formation of a polypeptide which in eukaryotes is regulated at following levels:

(i) transcriptional level (formation of primary transcript)

(ii) processing level (regulation of splicing)

(iii) transport of mRNA from nucleus to the cytoplasm

(iv) translational level.

(page-115)

In prokaryotes, control of the rate of transcriptional initiation is the predominant site for control of gene expression.

In a transcription unit, the activity of RNA polymerase at a given promoter is in turn regulated by interaction with accessory proteins.

(page-116)