Question

The sequence of one strand of DNA is 3' TCGATC 5'. What is the sequence of the complementary strand?

O 5' AGCTAG 3
O 5' TCGATC 3'
O 3' AGCTAG 5'
O 3' TCGATC 5'

Answer 1

A) 5' AGCTAG 3'

Step-by-step explanation:

DNA strands are antiparallel meaning that 3' to 5' has a complementary strand from 5' to 3'. This means that the last two answers can be eliminated because you can't have the 3' side pair up with a 3' side.

the other thing to remember is one of Chargaff's rules:

- A pairs with T

- G pairs with C

When writing a complementary strand's sequence, you must "convert" the letter in the original sequence to the letter that it is paired with by Chargaff's 2nd rule.