Question

How many DNA molecules of 6 base pairs length are possible where the first base is a purine and the last base is a pyrimidine?

Answer 1

Answer:

1024

Explanation:

This is a question of combination.

In the first and last places, only purines or pyrimidines can be present. So 2! for those two. The four places in between can have anything from the four bases,A,T,G,C.

Hence,

2!*4c1*4c1*4c1*4c1*2! = 1024.