    Question

# There are 20% adenine among the bases in a DNA fragment measuring 6.8 nm in length. The number of pentose sugars, nitrogen base pairs, phosphate groups and hydrogen bonds in this DNA fragment are respectively.

A
52,20,20,40
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B
40,52,40,20
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C
20,40,52,40
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D
40,20,40,52
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Solution

## The correct option is D 40,20,40,52The given DNA measure = 6.8nm = 68 Angstroms.Length of DNA = Distance between base pairs Total number of base pairsTherefore, 68 = 3.4 Total number of nitrogen base pairs.So the total number of nitrogen base-pair = 20Hence, nucleotides = 401 nucleotide = 1 nitrogen base + 1 pentose sugar + 1 phosphate groupsSo, pentose sugar = 40Phosphate groups = 40From the percentage mentioned these are 8 combinations of A-T and 12 combinations of C=G in the given fragment of DNA. Adenine is paired to thymine by two hydrogen bonds and cytosine is paired to guanine by three hydrogen bonds.So 8 2 = 16 and 12 3 = 3616+ 36 = 52 hydrogen bonds. So the correct answer in the sequence is option D.  Suggest Corrections  0      Similar questions
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