Question

A 100 base pair double strand is 20% A

1. How many bases ( in number) are T?

2. What percentage of bases are C?

3. How many hydrogen bonds hold the strands together?

Answer 1

1. As double stranded DNA has 20% A , it mean there will be 20% T (According to charlies's rule states that DNA from any cell of all organisms should have a 1:1 ratio base pair i . e A equals to T and G equals to C or purine=pyrimidine)

So A=T i.e 20%T will be there which means out of 100 base pairs, 20 base pairs of T should be there i.e 40 bases of T will be there.

2. Total A+T in double stranded DNA =20+20=40%

Total G+ C in double stranded DNA= 100-40=60%

Percentage bases of C =60%/2 =30%

3. There are two H- bonds between A and T , three H- bonds between G and C, so

Total number of H- bonds= (40x2)+(60x3)=80+180=260 H- bonds.