Question

A strand of DNA has the following sequence: 5'-ACTGCCTATGCT-3'.
What is the complementary strand that will be formed when the molecule undergoes replication during the M phase of the cell cycle?

• A. 5'-TGACGGATACGA- 3'
• B. 3' -TGACGGATACGA- 5'
• C. 5'-ACTGCCTATGCT-3'
• D. 3'-ACTGCCTATGCT- 5'
• E. 3'-UGACGGAUACGA-5'

Answer 1

Answer: (B)

3' -TGACGGATACGA- 5'

In DNA, Adenine (A) pairs with Thymine (T) and Guanine (G) pairs with Cytosine (C).

Hence, on replication of DNA in M phase, complementary nucleotides for each base pair will be added as follows:

A - T

T - A

G - C

C - G

Since replication occurs in 5'-3' direction, so the complementary strand will be formed in 3'-5' direction.

Hence the sequence of complementary strand formed upon replication will be: 3'-TGACGGATACGA-5'

So, the correct answer is 3'-TGACGGATACGA-5'.