Bio4

What is a chromatid?

• a special region that holds two centromeres together

• a chromosome in G₁ of the cell cycle

• a chromosome found outside the nucleus

• a replicated chromosome

What is the role of primase during DNA replication?

• synthesize RNA nucleotides as a primer

• join Okazaki fragments together

• unwind the parental double helix

• stabilize the unwound parental DNA

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?

• synthesize RNA nucleotides to make a primer

• unwind the parental double helix

• join Okazaki fragments together

• stabilize the unwound parental DNA

What is the function of topoisomerase?

• relieving strain in the DNA ahead of the replication fork

• elongation of new DNA at a replication fork by addition of nucleotides to the existing chain

• the addition of methyl groups to bases of DNA

• unwinding of the double helix

A new DNA strand elongates only in the 5' to 3' direction because

• the polarity of the DNA molecule prevents addition of nucleotides at the 3' end.

• Okazaki fragments prevent elongation in the 3' to 5' direction.

• replication must progress toward the replication fork.

• DNA polymerase can only add nucleotides to the free 3' end.

The leading and the lagging strands differ in that

• the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.

• the leading strand is synthesized by adding nucleotides to the 3' end of the growing strand, and the lagging strand is synthesized by adding nucleotides to the 5' end.

• the leading strand is synthesized continuously, whereas the lagging strand is synthesized in short fragments that are ultimately stitched together.

The Y-shaped structure where the DNA double helix is actively unwound during DNA replication is called the

• replication fork

• replication Y

• unwinding point

• Y junction

Which enzyme catalyzes the elongation of a DNA strand in the 5' ^__> 3' direction?

• primase

• DNA Ligase

• DNA Polymerase

• Topiosomerase

The strands that make up DNA are antiparallel. This means that

• the twisting nature of DNA creates nonparallel strands.

• the 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.

• the 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.

• one strand contains only purines and the other contains only pyrimidines.

In an analysis of the nucleotide composition of DNA, which of the following is true?

• A=C

• A=G and C=T

• A+C = G+T

• G+C=T+A