GATE XL topic:microbial-genetics PYQs & Answers

Questions 1–10 of 26. Imported answers require independent review unless marked reviewed.

In Escherichia coli, the minimum number of crossovers required between F⁻ genome and the linear DNA transmitted by Hfr to form a viable recombinant is _____. (Answer in integer)

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When tryptophan level is low in Escherichia coli, the expression of tryptophan biosynthesis genes is turned on through an antiterminator stem-loop formation between

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regions 1 and 2 of the leader sequence (trpL) of mRNA.

regions 2 and 3 of the leader sequence (trpL) of mRNA.

regions 2 and 4 of the leader sequence (trpL) of mRNA.

regions 3 and 4 of the leader sequence (trpL) of mRNA.

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The effect of mutations in a gene at their transcriptional and translational levels were analyzed using Northern (N) and Western (W) blot techniques, respectively. The following figure shows the schematic representation of mRNA and protein expression profiles of the wild-type and its four different mutants. Which one of the following mutants contains mutation in the upstream regulatory region of the gene?

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Mutant-1

Mutant-2

Mutant-3

Mutant-4

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In bacteriophage lambda (λ) life cycle, binding of Cro protein to cI gene operator region

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activates cI gene expression.

directs towards the lysogenic state.

directs towards the lytic cycle.

prevents cI gene expression.

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The origin of the Escherichia coli chromosome on the genetic map is shown below.

Bidirectional replication is a feature of this system and both replication forks move at the same rate. Which one of the following sequences of replication of the genes is correct?

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ABCDEF G

ABFCDE

GAFBCD

GAFBDE

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A culture of lac

Escherichia coli is grown in a medium lacking lactose or any other β-galactoside. The response of the lac operon upon induction by lactose can be monitored by measuring the levels of lac mRNA, β-galactosidase enzyme and permease enzyme. Which one of the following profiles correctly captures the on-off response to lactose?

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Which one of the following double-stranded sequences will NOT be recognized by a Type IIP restriction endonuclease?

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5′--GTACC--3′ 3′--CTAGG--5′

5′--GATCC--3′ 3′--CTAGG--5′

5′--CATAG--3′ 3′--GTATC--5′

5′--GATTC--3′ 3′--CTAAG--5′

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Which of the following event(s) occur(s) during translation in prokaryotes?

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tRNA binding to the start codon of mRNA on the 30s subunit of ribosome

Anticodon of tRNA binding to the start codon of mRNA on the 50s subunit of ribosome

The ribosome continues to move along the mRNA to add new amino acids to the polypeptide

The polypeptide is released when the ribosome reaches the stop codon

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Which of the following is/are consequence(s) of nitrous acid (HNO₂) mediated deamination?

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Deamination of cytosine, adenine and guanine

GC-to-AT transitions

AT-to-GC transitions

Addition of alkyl group to the bases

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Which of the following is/are TRUE about the Escherichia coli chromosome?

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It is typically bound by histones

It is circular in nature

It is found in the nucleoid

It contains multiple origins of replication

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GATE XL topic:microbial-genetics PYQs

How to practice topic:microbial-genetics

Question 72

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