(i) A DNA segment has a total of 1000 nucleotides, out of which 240 of them are adenine containing nucleotides. How many pyrimidine bases this DNA segment possesses?
(i) According to Chargaff s rule, ratio of purines to pyrimidines is equal, i.e. A + G = C + T
Since, the number of adenine (A) is equal to the number of thymine (T) and A = 240 (given)
Therefore, T = 240
Also, the number of guanine (G) is equal to cytosine ©. Thus, G + C = 1000 - (A + T)
G + C = 1000-480 = 520 Hence, G = 260, C = 260
The number of pyrimidine bases, i.e. C + T (2)
= 240 + 260 = 500