Question

(a) A DNA segment has a total 1000 nucleotides, out of which 240 of them are adenine containing nucleotides. How many pyrimidine bases this DNA segment possesses ?

Answer 1

(a) adenine (A) always pairs with Thymine (T) and Cytosine (C) always pairs with Guanine (G). Purines = Adenine and Guanine , Pyrimidines = Cytosine and Thymine
`therefore` If 240 adenine are there in the DNA segment, then there will be 240 thymine available to pair with them, making a total of 480 in the segment.
`therefore` The remaining nucleotides = 1000 - 480 = 520
So, there will be 260 cytosine and 260 guanine nucleotides in that segment, making 520 in total. Therefore, total number of pyrimidines in a DNA segment = 260 cytosine + 240 Thymine = 500