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
B)40,52,40,20
C)20,40,52,40
D)40,20,40,52

Answer 1

Hint: DNA fragmentation was first recognized by Williamson in 1970 when he observed discrete oligomeric fragments consisting in the cell death in primary neonatal liver cultures.

Complete answer:
DNA fragmentation is the process of division or breaking of DNA strands into pieces. It can be done purposely by laboratory personnel or by cells or it can occur suddenly. Spontaneous or accidental DNA fragmentation is the fragmentation that progressively accumulates in a cell.
Here, the given DNA measures about 6.8nm = 68 Angstroms.
Length of DNA equals Distance between base pairs × Total number of base pairs
so, 68 A˚ = 3.4A˚ × Total number of nitrogen base pairs.
Thus, nucleotides = 40
1 nucleotide is equal to 1 nitrogen base + 1 pentose sugar + 1 phosphate groups,
Therefore , pentose sugar = 40
Phosphate groups = 40
From the percent mentioned these are 8 combinations of A-T and 12 combinations of C=G in a given fragment of DNA. Adenine is paired to thymine by two hydrogen bonds and cytosine is paired to guanine by 3 hydrogen bonds.
consequently 8× 2 = 16 and 12 × 3 = 36
16+ 36 = 52 hydrogen bonds.

Hence, the correct answer is option (D)

Note: 1)DNA Fragmentation also plays an important part in forensics.
2)It is very essential for DNA profiling technology. So they are generally considered as an important process.