Question

What is the complementary strand of DNA for the given nitrogenous bases?

a) 3-adenine, cytosine, cytosine, thymine-5'
b) 5-thymine, adenine, adenine, guanine-3'
c) 5-thymine, guanine, guanine, adenine-3'
d) 3-adenine, guanine, guanine, thymine-5'

Answer 1

DNA strands follow complementary base pairing rules with adenine (A) pairing with thymine (T), and guanine (G) pairing with cytosine (C), in an antiparallel fashion. The correct complementary DNA strands for the provided sequences are opposite in direction to the given sequences.

Step-by-step explanation:

The question pertains to the concept of complementary base pairing in a DNA molecule, which is governed by specific pairing rules where adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C). Because DNA strands are antiparallel, the complementary strand is created in the opposite direction. Therefore, for each given sequence, the complementary strand would be:

a) 5'-TGGGAA-3'

b) 3'-ACTTTG-5'

c) 3'-ACCAAG-5'

d) 5'-TCACCACAA-3'

Note that for option a) and d), the complementary strand starts with a 5' end, whereas for options b) and c), it starts with a 3' end, reflecting the antiparallel structure of DNA.