Chapter 12: DNA Replication and Recombination

A set of flashcards to review key concepts from Chapter 12 on DNA replication and recombination.

Why must replication be extremely accurate?

Because one error per million base pairs leads to 6,400 mistakes every time a cell divides, which could be catastrophic.

What is the replication speed of E. coli DNA?

E. coli replicates its DNA at a rate of 1,000 nucleotides per second.

What are the three proposed models of DNA replication?

Conservative replication model, dispersive replication model, and semiconservative replication model.

Who conducted the experiment that provided evidence for semiconservative replication?

Meselson and Stahl.

What isotopes of nitrogen were used in Meselson and Stahl’s experiment?

14N (common form) and 15N (rare, heavy form).

What is a replicon?

A unit of replication.

What is theta replication?

A type of replication occurring in circular DNA, such as in E. coli, with a single origin of replication forming a replication fork.

How does rolling-circle replication differ from theta replication?

Rolling-circle replication typically involves a single origin of replication and is one-directional, while theta replication can be bidirectional.

What is the role of DNA polymerase in replication?

It synthesizes a new DNA strand by adding nucleotides to the 3′ end.

What are Okazaki fragments?

Short DNA fragments synthesized discontinuously on the lagging strand during replication.

What is the function of DNA primase?

Synthesizes a short RNA primer to provide a 3′-OH group for the attachment of DNA nucleotides.

How does the mechanism of eukaryotic DNA replication differ from prokaryotic replication?

Eukaryotes have multiple origins of replication and their replication is bidirectional, while prokaryotes have a single origin and may be unidirectional.

What is the end-replication problem?

In eukaryotes, when the RNA primer is removed at the ends of linear chromosomes, there is no 3′-OH group for DNA polymerase to fill the gap.

What is the function of telomerase?

It adds repetitive sequences to the ends of linear chromosomes (telomeres) to prevent chromosome shortening.

What is homologous recombination?

A process where exchange is between homologous DNA molecules during crossing over.

What is the significance of proofreading during DNA replication?

It allows DNA polymerase to remove incorrectly paired nucleotides, ensuring fidelity in DNA synthesis.

What is the result of cleavage at a Holliday junction?

It can produce either crossover or noncrossover recombinant DNA, depending on the cleavage plane.

How does the structure of eukaryotic chromatin affect DNA replication?

Eukaryotic DNA is complexed to histone proteins, requiring nucleosome reassembly after replication.