THE MOLECULAR BASIS OF INHERITANCE
STRUCTURE OF NUCLEIC ACIDS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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4
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10
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16
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64
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Detailed explanation-1: -The variation of energy with the twist of the base pairs about the helix axis shows the straight DNA free in solution is most stable with about 10 1/2 base pairs per turn rather than 10 as observed in the solid state, whereas superhelical DNA in chromatin is most stable with about 10 base pairs per turn.
Detailed explanation-2: -The DNA double helix biopolymer of nucleic acid is held together by nucleotides which base pair together. In B-DNA, the most common double helical structure found in nature, the double helix is right-handed with about 10–10.5 base pairs per turn.
Detailed explanation-3: -There are 10 base pairs in one turn of helix. The length of the helix is 3.4 x 10 = 34 Ao.
Detailed explanation-4: -in chromatin, the structure is most stable with about 10 base pairs per turn. This result explains both the 10-base-pair repeat observed in partial nuclease digests of nucleosomes (8) and also the change in DNA linkage observed when nucleosomes are formed (9, 10).
Detailed explanation-5: –Z-DNA: Z DNA is a left handed helical structure with 4.4nm turn length and 12 bases in each turn. The presence of Z-DNA occurs in some enhancers. Thus the correct answer is (B). The number of bases in each turn of Z-DNA and B-DNA helices respectively is 12 and 10.