Question

Determine the number of hydrogen and phosphodiester bonds present in the following DNA fragment: 5-CAGCTG-3 3-GTCGAC-5 hydrogen bonds= 16; phosphodiester bonds= 10 hydrogen bonds=14; phosphodiester bonds=5 O hydrogen bonds= 10; phosphodiester bonds= 5 hydrogen bonds= 12; phosphodiester bonds-6

Answer 1

Ans) The number of hydrogen bonds present are 16 and number of phosphodiester bonds present are 10.

So, option 1 is correct.

Explanation :

The number of hydrogen bonds between G and C are 3 and between A and T are 2. There are 4 GC pairs and 2 AT pairs.

So, number of hydrogen bonds between G and C pairs are 4 X 3 = 12 bonds

and number of hydrogen bonds between A and T pairs are 2 X 2 = 4 bonds

Therefore, total hydrogen bonds present in 5'- CAGCTG-3' are 12 + 4 = 16 bonds.

   3'- GTCGAC-5'

1 Phosphodiester bond is present between two nucleotide bases. So, number of phosphodiester bonds present in one strand 5'- CAGCTG-3' are 5 ( between C and A, A and G, G and C, C and T, T and G) and in the other stand  3'- GTCGAC-5' are 5 ( between G and T, T and C , C and G, G and A, A and C).

So, total 10 phosphodiester bonds are present.