The DNA & RNA World

1 Mark Questions

1. What will happen if DNA replication is hot followed by cell division in a eukaryotic cell? [All India 2014 c]

Ans. If cell division is not followed after DNA replication then replicated chromosomes (DNA) would not be distributed to daughter nuclei. A repeated replication of DNA without any cell division results in the accumulation of DNA inside the cell. This would increase the volume of the cell nucleus, thereby causing cell expansion,

1. Name the specific components and the linkage between them that form deoxyadenosine. [Delhi 2013c]

Ans. Adenine (N-glycosidic Linkage) + Deoxyribose -> Deoxyadenosine

1. Which one out of rho factor and sigma factor act as an initiation factor during transcription in a prokaryote? [Delhi 2013 C]

Ans. Sigma factor acts as an initiation factor during transcription in prokaryotes

1. Name the enzyme involved in continuous replication of DNA strand. Mention the polarity of the template strand. [All India 2012]

Ans. Enzyme involved in continuous replication of DNA strand is DNA polymerase. Template strand has 3'->5' polarity

1. Name the positively charged protein around which the negatively charged DNA wrapped.[All India 2012 C]

Ans. Histones are the positively charged proteins around which the negatively charged DNA wrapped.

6.A structural gene has two DNA strands X and Y shown below. Identify the template strand. [HOTS; All India 2010 C]

x) /r

Ans.'X' is template strand. It is because the template strand has the polarity in 3' -> 5' direction.

1. Why is hnRNA required to undergo splicing? [HOTS; Delhi 2009]

Ans.hnRNA is required to undergo splicing because of the introns (the non-coding sequences). These are needed to be removed and the exons (the coding sequences) have to be joined in a specific sequence.

1. Mention the two additional processes, which hnRNA needs to undergo after splicing so, as to become functional. [Delhi 2009]

Ans. The additional processes bnRNA needs to undergo after splicing are capping and tailing.

1. When and at what end does the tailing of hnRNA takes place? [All India 2009]

Ans. When hnRNA is processed to make mRNA, tailing takes place at the 3'-end.

10.At which ends do capping and tailing of hnRNA occur respectively? [Foreign 2009] Ans.Capping – At 5'-end Tailing -At 3'-end

1. How is the length of DNA usually Calculated? [All India 2009 C]

Ans. Length of DNA can be calculated by simply multiplying the total number of base pair with distance between two consecutive bp,

i.e.6.6x <math>10^9</math>bpx <math>0.34x 10^{-9}</math>m/bp.

It comes about <math>2.2 \text{ m}</math>. <math>(0.34 \times 10^{-9} \text{ m})</math> is the distance between two consecutive base pairs)

1. Name the parts A and B of the transcription unvit given below.

Structural gene 3' Α

3′ Ť В

Ans. A - Promoter, 8-Coding strand.

1. Name the components A and B in the nucleotide with a purine, given below.

---- Н [Delhi 2008; Foreign 2008]

Ans.A – Phosphate B-Any nitrogenous base (e.g. adenine, guanine, cytosine or thymine).

1. Name the type of synthesis A and B occurring in the replication fork of DNA as shown below. [Delhi 2008]

5′ Ans.A – Continuous synthesis (Leading strand) B – Discontinuous synthesis (Lagging strand)

15.Mention the polarity of the DNA strands A-B and C – D shown in the replicating fork given below.

[Ail India 2008] В D Ans. <math>A - B = 3' -> 5' C - D = 5' -> 3'</math>