Question

If a stretch of DNA on the parental strand of a replicating chromosome has the sequence

5′-AGCTCGATCGGCTA-3′, what will the sequence of the newly synthesized strand made from this stretch of template be?

A. 5′-AGCTCGATCGGCTA-3′

B. 3′-AGCTCGATCGGCTA-5′

C. 5′-TCGAGCTAGCCGAT-3′

D. 3′-TCGAGCTAGCCGAT-5′

Answer 1

The sequence of the newly synthesized DNA strand complementary to the parental strand 5′-AGCTCGATCGGCTA-3′ is 3′-TCGAGCTAGCCGAT-5′, which is option D.

Step-by-step explanation:

If the stretch of DNA on the parental strand of a replicating chromosome has the sequence 5′-AGCTCGATCGGCTA-3′, then the sequence of the newly synthesized strand made from this stretch of template will be complementary to it. DNA polymerase synthesizes new DNA strands in the 5′ to 3′ direction, using each base on the template strand to guide the addition of the complementary base on the new strand.

Thymine (T) pairs with adenine (A), and cytosine (C) pairs with guanine (G).The sequence of the newly synthesized strand, which is complementary to the parental 5′-AGCTCGATCGGCTA-3′ strand, would be written in the 3′ to 5′ direction as the reverse complement: 3′-TCGAGCTAGCCGAT-5′. Therefore, the correct answer is D. 3′-TCGAGCTAGCCGAT-5′.