Molecular Biology Mcqs

Q:

How many subunits of Spo11 are involved in the process of cleavage of DNA?

A) 1 B) 2
C) 3 D) 4
 
Answer & Explanation Answer: B) 2

Explanation: The two subunits of Spo11 cleave the DNA two nucleotides apart on the two DNA strands. It makes staggered double strand break by cleavage.

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22
Q:

What is the function of the Spo11 in meiotic recombination?

A) Introduction of mutation B) Introduction of nick
C) Introduction of DSB D) Introduction of lesion
 
Answer & Explanation Answer: C) Introduction of DSB

Explanation: Spo11 gene encodes a protein that introduces DSBs in chromosomal DNA to initiate meiotic recombination. The Spo11 protein cuts the DNA at many chromosomal locations with little sequence selectivity but at a very specific time during meiosis.

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22
Q:

What are homologs?

A) Part of DNA B) Pair of nucleus
C) Pair of chromosomes D) Part of a cell
 
Answer & Explanation Answer: C) Pair of chromosomes

Explanation: Before cell division the cell has two copies of each chromosome, one of each was inherited from either parent. These are known as homologs.

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30
Q:

For which biological phenomenon homologous recombination is critical?

A) Mitosis B) Meiosis
C) Fragmentation D) Sporing
 
Answer & Explanation Answer: B) Meiosis

Explanation: Homologous recombination is critical for meiosis during the pachytene stage of meiosis I. This is important for the introduction of genetic variations in every generation.

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14
Q:

What is non-disjunction?

A) Proper alignment B) Sister chromatid formation
C) Failed alignment D) Chromosome segregation
 
Answer & Explanation Answer: C) Failed alignment

Explanation: The absence of recombination leads to the failed alignment of the chromosomes in the 1st meiotic division and as a result there is a high incidence of chromosome loss. This improper segregation of chromosomes is called nondisjunction.

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19
Q:

How many cycles are required for the configuration of chromosomes?

A) 1 B) 2
C) 3 D) 4
 
Answer & Explanation Answer: B) 2

Explanation: Chromosomes are configured during two division cycles. This is because meiosis involves two rounds of nuclear divisons.

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18
Q:

Processing of the DNA at the break site occurs at the 3’ end.

A) True B) False
 
Answer & Explanation Answer: B) False

Explanation: Processing of the DNA at the break site occurs exclusively at the 5’ terminus. The strand ic covalently attached to the Spo11 protein.

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14
Q:

What are the components of the MRX protein?

A) MreII, Rad50, Xrs2 B) Rad51, Rad52, Rad59
C) RecA, RuvC, RuvAB D) Rad51C, WRN, BLH
 
Answer & Explanation Answer: A) MreII, Rad50, Xrs2

Explanation: MRX enzyme complex is used for the event of DNA processing. It is composed of protein subunits, MreII, Rad50 and Xrs2. The first letters of the subunits give the complex its name.

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