CLEP Biology DNA Structure and Replication 4

Question 1

Which of the following correctly pairs a base with its complementary base in DNA?

Accepted Answer

Guanine — Cytosine

Answer

In DNA, guanine pairs with cytosine (3 H-bonds) and adenine pairs with thymine (2 H-bonds); uracil is found only in RNA.

Question 2

The 3' to 5' exonuclease activity of DNA polymerase I serves which function?

Accepted Answer

Proofreading to remove incorrectly incorporated nucleotides

Answer

The 3'→5' exonuclease activity of DNA polymerase removes mismatched nucleotides just added during synthesis, providing proofreading ability.

Question 3

In eukaryotes, DNA replication begins at:

Accepted Answer

Multiple origins of replication along each chromosome

Answer

Eukaryotic chromosomes are large, so they have multiple origins of replication that fire simultaneously to complete replication in a reasonable time.

Question 4

Which of the following bonds holds the two strands of the DNA double helix together?

Accepted Answer

Hydrogen bonds between complementary bases

Answer

The two strands are held together by hydrogen bonds between complementary base pairs (A-T: 2 bonds; G-C: 3 bonds).

Question 5

What type of bond connects adjacent nucleotides within a single DNA strand?

Accepted Answer

Phosphodiester bond

Answer

Phosphodiester bonds form between the 3'-OH of one nucleotide and the 5'-phosphate of the next, creating the sugar-phosphate backbone.

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