NEET Practice Questions (MCQs) with Answers & Solutions

Bacteria, chloroplast and mitochondria consists of circular DNA.

A + G + C + T = 100%

Because  = G = 18%

A + 18% + 18% + T = 100%

A + T = 64%

as A = T

A = 32% and T = 32%

Therefore adenine would be 32%.

¹⁴NH4Cl : the heavy isotope of nitrogen and ¹⁵NH4Cl were used in

semiconservative DNA replication experiment by Matthew Meselson and

Franklin Stahl in 1958.

(page-104)

In prokaryotes, such as, E. coli, the DNA is not scattered throughout the

cell. Double-stranded DNA is held with some proteins in a region termed as

‘nucleoid’. The DNA in nucleoid is organised in large loops held by proteins.

(page-99)

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