Given the partial sequence of a single DNA strand shown below, what will be the...
Given the partial sequence of a single DNA strand shown below, what will be the sequence of the complementary strand that is produced during DNA replication? 3' - ATCGAAGTGC - 5'
- A. 5' - TAGCTTCACG - 3'
- B. 5' - UAGCUUCACG - 3'
- C. 5' - ATCGAAGTGC - 3'
- D. 3' - UAGCUUCACG - 5'
Correct Answer: A. 5' - TAGCTTCACG - 3'
Explanation
The question specifies that this is DNA replication. U (uracil) is found only in RNA and T (thymine) is found only in DNA. In DNA, A (adenine) pairs with T (thymine) and G (guanine) pairs with C (cytosine) so the complementary strand will have A where the original has T, G where the original has C, C where the original has G and T where the original has A. DNA strands run antiparallel, so the 3' end on the new strand will go opposite the 5' end on the original and vice versa. In this case, that means the complementary strand will run from 5' to 3' to read 5' - TAGCTTCACG - 3'. This sequence is shown in bold below: