Question

If the base sequence in DNA is 5' AAAA 3',then the base sequence in m-RNA

• A. 5' UUUU 3'
• B. 3' UUUU 5'
• C. 5' AAAA 3'
• D. 3' TTTT 5'

Answer 1

Answer: (B)

3' UUUU 5'

We are aware of the fact that the formed mRNA from a strand of DNA will be similar to the complementary strand of DNA coding mRNA, except the base pair Thymine which will be replaced by Uracil in mRNA.

First, think about the base pairing in the complementary strand of DNA, it will be

3' TTTT 5'

As we know that the base pairs in mRNA and DNA are not same. The DNA consists of ATGC base pairs while in mRNA the Thymine is replaced by Uracil making its base pairs as AUGC.

So, it is known that wherever the complementary strand of a segment of DNA was having Thymine it will be replaced by Uracil in case of formed mRNA. So, the sequence of m-RNA will be

3' UUUU 5'.

So, the correct answer to the question is 3' UUUU 5'.