Biology DNA Structure and Replication Flashcards

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

Answer: Guanine — Cytosine

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

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

Answer: Proofreading to remove incorrectly incorporated nucleotides

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

In eukaryotes, DNA replication begins at:

Answer: Multiple origins of replication along each chromosome

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

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

Answer: Hydrogen bonds between complementary bases

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

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

Answer: Phosphodiester bond

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

Telomerase is particularly important in which type of cell?

Answer: Germ cells and stem cells, because they divide continuously

Telomerase extends telomeres using an RNA template, which is especially important in continuously dividing cells like germ cells and stem cells to prevent chromosomal shortening.

During DNA replication, which enzyme synthesizes the RNA primer on the lagging strand template?

Answer: Primase

Primase, a type of RNA polymerase, synthesizes short RNA primers complementary to the DNA template, giving DNA polymerase a 3'-OH to extend.