Question

Given below is the sequence of coding strand of DNA in a transcription unit 3 '- AATGCAGCTATTAGG - 5’.

Write the sequence of:

a) its complementary strand

b) the mRNA

Answer 1

a) Sequence of complementary strand:

The sequence of complementary strands can be determined by complementarity between the nitrogenous bases. If the sequence of the coding strand is 5’ - GGATTATCGACGTAA - 3’, then the sequence of the complementary strand is 3’ - CCTAATAGCTGCATT- 5’.

The Adenine (A) pairs with Thymine (T) with two hydrogen bonds and Guanine (G) pairs with cytosine (C) with three hydrogen bonds and vice versa.


b) Sequence of mRNA:

Sequence of the mRNA strand is the same as the sequence of the coding strand of DNA, only thymine in DNA is replaced by uracil in RNA.

If the sequence of the coding strand is 5’ - GGATTATCGACGTAA - 3’, then the sequence of mRNA is 5’ - GGAUUAUCGACGUAA-3’.