Question

Question #da8d2

Answer 1

Chargaff had 2 rules

1. The number of pyrimidines and purines must be equal
2. The number of C is about equal to G and A is about equal to T

Explanation:

The first rule of chargaff said that there had to be an equal number of purines and pyrimidines.

This is logical, as any purine is normally bound to its pyrimidine counterpart. The purine Adenine is complementary to the pyrimidine Thymine (and vice versa), whilst the purine Guanine is complementary to the pyrimidine Cytosine.

Following this is the second rule, which tells us that the ratio of A in the strand of DNA has to be roughly equal to the ratio of T in the DNA and the ratio of G is roughly equal to C.
I say roughly because mistakes can occur in the DNA. You can get deletions and mismatches which may raise/lower any one of the ratios.