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Molecular Basis Of Inheritance

Question
CBSEENBI12001893
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List the salient features of double helix structure of DNA. 

Solution

Watson and Crick proposed the double helix for structure of DNA. Its features are:

(i) It is made of two polynucleotide chains, where the sugar-phosphate constitutes the backbone, and the bases project inside.

(ii) The two chains have anti-parallel polarity. It means, if one chain has the polarity 5'-3', the other has 3'-5'.

(iii) The bases in two strands are paired through hydrogen bond (H-bonds) forming base pairs (bp). Adenine forms two hydrogen bonds with Thymine from opposite strand and vice-versa. Similarly, Guanine is bonded with Cytosine with three H-bonds. As a result, always a purine comes opposite to a pyrimidine. This generates approximately uniform distance between the two strands of the helix.

(iv) The two chains are coiled in a right-handed fashion. The pitch of the helix is 3.4 nm (a nanometre is one billionth of a metre, that is 10-9 m) and there are roughly 10 bp in each turn turn. Consequently, the distance between a bp in a helix is approximately equal to 0.34 nm.

(v) The plane of one base pair stacks over the other in double helix. 

Some More Questions From Molecular Basis of Inheritance Chapter

List the number of base pairs in :

(i) lambda bacteriophage

(ii) E.coli and

(iii) haploid content of human DNA.

Comment two chains of DNA have antiparallel polarity.

What is the difference between DNAs and DNAase ?

Which was first genetic material ?

Suggest one evidence to prove that RNA was first genetic material.

Why was RNA unstable ?

What made DNA more preferrable as genetic material ?

Process of replication is completed in how much time in E.coli ?

What is average rate of polymerization ?

List three components of transcription unit.

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