Practice Start Test

Molecular Basis of Inheritance

NEET Biology · 262 questions · Page 8 of 27 · Click an option or "Show Solution" to reveal answer

Q71
Gene and cistron words are sometimes used synonymously because
A one cistron contains many genes
B one gene contains many cistrons
C one gene contains one cistron
D one gene contains no cistron
Correct Answer
Option C
Solution

(c) Cistron is that segment of DNA which specifies synthesis of a polypeptide.

Q72
Types of RNA polymerase required in nucleus for RNA synthesis?
A 1
B 2
C 3
D 4
Correct Answer
Option C
Solution

(c) Eukaryotes have three types of RNA polymerases: RNA polymerase I (rRNA), RNA polymerase II (mRNA), RNA polymerase III (tRNA and 5S rRNA).

Q73
Exon part of mRNAs have code for
A protein
B lipid
C carbohydrate
D phospholipid
Correct Answer
Option A
Solution

(a) Exons are the coding part of mRNA.

Q74
Out of 64 codons, 61 codons code for 20 types of amino acid. It is called
A degeneracy of genetic code
B overlapping of gene
C wobbling of codon
D universility of codons
Correct Answer
Option A
Solution

(a) Out of 64 codons, only 3 signify stop codons.

There are more than one codon for most of the amino acids, the genetic code is non-overlapping.

Q75
Degeneration of a genetic code is attributed to the third member of a codon
A third member of a codon
B first member of a codon
C second member of a codon
D all members equally
Correct Answer
Option A
Solution

(a) According to the Wobble hypothesis, tRNA anticodon has the ability to wobble at its 5 end by pairing with even non-complementary base of mRNA codon.

It corresponds to third base degeneracy of the codons.

Q76
In the genetic code dictionary, how many codons are used to code for all the 20 essential amino acids?
A 60
B 20
C 64
D 61
Correct Answer
Option D
Solution

(d) Out of a total of 64 codons, 3 codons do not code for any amino acid.

Hence only 61 codons are used in the formation of the 20 standard amino acids (polypeptides).

Q77
What would happen if in a gene encoding a polypeptide of 50 amino acids, 25th codon (UAU) is mutated to UAA?
A A polypeptide of 25 amino acids will be formed
B A polypeptide of 24 amino acids will be formed
C Two polypeptides of 24 and 25 amino acids will be formed
D A polypeptide of 49 amino acids will be formed
Correct Answer
Option B
Solution

(b) UAA is the stop codon.

Therefore at 25th amino acid the synthesis of polypeptide stops.

So, a polypeptide of 24 amino acids is formed.

Q78
Which one of the following triplet codes, is correctly matched with its specificity for an amino acid in protein synthesis or as start or stop codon?
A UAC - Tyrosine
B UCG - Start
C UUU - Stop
D UGU - Leucine
Correct Answer
Option A
Solution

(a) AUG is initiation codon. UCG codes for serine, UUU codes for phenylalanine, UGU codes for cysteine.

Q79
During translation initiation in prokaryotes, a GTP molecule is needed in
A association of 50S50 S subunit of ribosome with initiation complex
B formation of formyl-met-tRNA
C binding of 30S30 S subunit of ribosome with mRNA
D association of 30S−mRNA30 S-mRNA with formylmet-tRNA
Correct Answer
Option A
Solution

(a) For the formation of initiation complex during translation of mRNA, GTP is also required.

The initiator AUG codes for the formylmethionine in prokaryotes.

Q80
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 begins at the ori - origin of replication and proceeds on both sides from the ori.

Unidirectional replication is rare.

RNA primers are involved in both prokaryotes and eukaryotes.

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