Molecular Basis of Inheritance — Page 13 | NEET Biology

Q121

Which one of the following triplet codes, is correctly matched with its specificity for an amino acid?

A UAC - Tyrosine

B UCG - Start

C UUU - Stop

D UGU - Leucine

Correct Answer

Option A

Solution

(a) UAC codes for tyrosine; UCG codes for serine; UUU codes for phenylalanine; UGU codes for cysteine.

Q122

During replication of a bacterial chromosome DNA synthesis starts from a replication origin site and

A RNA primers are involved

B is facilitated by telomerase

C moves in one direction of the site

D moves in bi-directional way

Correct Answer

Option D

Solution

(d) Replication proceeds bidirectionally from the origin of replication.

Q123

The telomeres of eukaryotic chromosomes consist of short sequences of

A thymine rich repeats

B cytosine rich repeats

C adenine rich repeats

D guanine rich repeats

Correct Answer

Option D

Solution

(d) Telomeres consist of guanine-rich repeats (TTAGGG in vertebrates).

Q124

In a mutational event, when adenine is replaced by guanine, it is a case of

A frame shift mutation

B transcription

C transition

D transversion

Correct Answer

Option C

Solution

(c) Transition: purine replaced by purine (A→G) or pyrimidine by pyrimidine.

Q125

Experimental material in the study of DNA replication has been

A Escherichia coli

B Neurospora crassa

C Pneumococcus

D Drosophila melanogaster

Correct Answer

Option A

Solution

(a) Meselson and Stahl (1958) raised Escherichia coli on ammonium chloride having heavy isotope of nitrogen for several generations to study semi-conservative replication of DNA.

Q126

Khorana first deciphered the triplet codons of DNA

A serine and isoleucine

B cysteine and valine

C tyrosine and tryptophan

D phenylalanine and methionine

Correct Answer

Option B

Solution

(b) Hargobind Khorana first deciphered the triplet codon for valine, while cysteine was deciphered by Robert W. Holley.

Q127

Escherichia coli fully labelled with

{ }^{15} N

is allowed to grow in

{ }^{14} N

medium. The two strands of DNA molecule of the first generation bacteria have

A different density and do not resemble parent DNA

B different density but resemble parent DNA

C same density and resemble parent DNA

D same density but do not resemble parent DNA

Correct Answer

Option C

Solution

(c) After one generation in ${ }^{14} N$ medium DNA of bacteria settled at a level intermediate between heavy and light bands due to semi conservative DNA replication.

Q128

Telomerase is an enzyme which is a

A simple protein

B RNA

C ribonucleoprotein

D repetitive DNA

Correct Answer

Option C

Solution

(c) Telomerase is a ribonucleoprotein reverse transcriptase that elongates telomeres.

Q129

Because most of the amino acids are represented by more than one codon, the genetic code is

A overlapping

B wobbling

C degenerate

D generate

Correct Answer

Option C

Solution

(c) All amino acids are specified by more than one codon (except Tryptophan and Methionine). Hence they are degenerate.

Q130

During DNA replication, the strands separate by

A DNA polymerase

B topoisomerase

C unwindase/Helicase

D gyrase

Correct Answer

Option C

Solution

(c) Unwindase or helicase takes part in separation of two DNA strands.

In prokaryotes, helicase or unwindase is assisted by gyrase in this function.