Molecular Basis of Inheritance — Page 7 | NEET Biology

Q61

What base is responsible for hot spots for spontaneous point mutations?

A Adenine

B 5-bromouracil

C 5-methylcytosine

D Guanine

Correct Answer

Option C

Solution

(c) The term hot spots was used by Benzer for the sites which are more mutable than other sites.

Studies in 1978 revealed that 5-methylcytosine residues occur at the position of each hot spot.

Q62

Which of the following is required as inducer(s) for the expression of Lac operon?

A Glucose

B Galactose

C Lactose

D Lactose and galactose

Correct Answer

Option C

Solution

(c) Lac operon is an inducible operon.

Lactose is the substrate for the enzyme beta-galactosidase and it also regulates switching on and off of the operon.

Hence, it is termed as inducer.

Inducer functions by disabling repressors.

The gene is expressed because an inducer binds to the repressor.

The binding of the inducer to the repressor prevents the repressor from binding to the operator.

RNA polymerase can then begin to transcribe structural genes.

Q63

Spliceosomes are not found in cells of;

A Fungi

B Animals

C Bacteria

D Plants

Correct Answer

Option C

Solution

(c) In eukaryotes, spliceosomes are used in removal of introns during post-transcriptional processing of hnRNA.

They are absent in prokaryotes.

Q64

All of the following are part of an operon except

A an operator

B structural genes

C a promoter

D an enhancer

Correct Answer

Option D

Solution

(d) Unlike eukaryotes in prokaryotes the genes are organised into operon.

Operon is a co-ordinated group of genes which are all transcribed together & regulate a metabolic pathway as a unit.

Q65

Under which of the following conditions will there be no change in the reading frame of following mRNA? 12 AACAGCGGUGCUAUU 3

A Insertion of

G

at

5^{\text{th }}

position

B Deletion of

G

from

5^{\text{th }}

position

C Insertion of

A

and

G

at

4^{\text{th }}

and

5^{\text{th }}

positions respectively

D Deletion of GGU from

7^{\text{th }}, 8^{\text{th }}

and

9^{\text{th }}

positions

Correct Answer

Option D

Solution

(d) There will be no change in reading frame of m-RNA by deletion of GGU from $7^{\text{th }}, 8^{\text{th }}$ , and $9^{\text{th }}$ position.

Q66

DNA replication is

A conservative and discontinuous

B semiconservative and semidiscontinuous

C semiconservative and discontinuous

D conservative

Correct Answer

Option C

Solution

(c) In semi-conservative replication of DNA, each replica contains one half of the old strand and one half of a new strand synthesised over it.

Also, one strand is synthesised continuously and the other discontinuously, hence called discontinuous.

Q67

Initiation codon of protein synthesis (in eucaryotes) is

A GUA

B GCA

C CCA

D AUG

Correct Answer

Option D

Solution

(d) The initiation codon is the codon which initiates the protein synthesis.

They are AUG for methionine and GUG for valine.

Q68

Anticodon is an unpaired triplet of bases in an exposed position of

A mRNA

B rRNA

C tRNA

D sRNA

Correct Answer

Option C

Solution

(c) tRNA works as an adaptor molecules for carrying amino acid to the mRNA template during protein synthesis.

It bears anticodon and recognises the specific codon on mRNA.

Q69

One function of the telomeres in a chromosome is to

A indentify the correct number of the homologous pair of chromosomes

B help two chromatids to move towards poles

C seal the ends of chromosomes

D start RNA synthesis

Correct Answer

Option C

Solution

(c) The telomere is a region of repetitive nucleotide sequences at each end of a chromosome which acts to protect the terminal ends of chromosomes.

Q70

Mutation generally produces genetic variation

A polygenes

B dominant alleles

C recessive genes

D lethal genes

Correct Answer

Option C

Solution

(c) Mutation generally produces recessive genes as genetic variation.