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Structural Basis of DNA Replication

Why does each base in DNA have a complementary base? Complementary bases are a key feature of DNA structure. Adenine and thymine are complementary to one another as are guanine and cytosine. There are two important reasons why DNA is composed of complementary bases. The first is that only with complementary bases can the two strands of DNA have complementary sequences. Without the complementary sequences DNA replication as we know it would be impossible. The second reason is that the pairs of bases are complementary because their chemical structure allows for strong hydrogen bonding and they fit together well. The strong association between complementary bases makes DNA a stable molecule and aids in the detection of errors in DNA synthesis.

View the animation below, then complete the quiz to test your knowledge of the concept.

1DNA replication is said to be

2Which of the following DNA sequences is complementary to 5’ TAGAC 3’?
A)5’ TAGAC 3’
B)5’ ATCTG 3’
C)5’ GTCTA 3’
D)5’ CAGAT 3’
E)none of the above

3According to Chargaff’s rule, which of the following statements about double-stranded DNA is TRUE?
A)A = T and C = G
B)A + G = C + T
C)A + T = C + G
D)A and B
E)A, B, and C

4The newly-synthesized strand of DNA has exactly the same base sequence as that of its template strand.

5The DNA replication machinery is assembled at the replication fork.

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