DNA Replication, Repair, and Recombination

These flashcards cover key concepts related to DNA replication, repair, recombination, and related enzymatic functions.

What is the role of DNA polymerases in DNA replication?

DNA polymerases promote the formation of phosphodiester linkages and participate in DNA replication and repair.

What direction does DNA polymerase elongate a new DNA strand?

5′ to 3′ direction.

What is required for DNA polymerase to begin synthesis of a new DNA strand?

A primer strand with a free 3′-OH group.

How do DNA polymerases ensure fidelity during DNA replication?

By removing mismatched nucleotides through exonuclease activity.

What are Okazaki fragments?

Short discontinuously synthesized DNA strands formed on the lagging strand during DNA replication.

What does processivity refer to in the context of DNA polymerase?

The ability of an enzyme to catalyze many consecutive reactions without releasing the substrate.

What is the primary enzyme responsible for DNA synthesis in E. coli?

DNA polymerase III.

How are gaps between Okazaki fragments on the lagging strand filled?

By DNA polymerase I, which removes the RNA primer and fills the gaps with DNA.

What is the function of helicases during DNA replication?

To separate the DNA strands by unwinding the double helix using ATP hydrolysis.

What is the role of telomerase in eukaryotic cells?

To replicate and maintain the length of telomeres, preventing chromosome shortening.

What are the potential consequences of DNA damage?

Cell transformation, inheritable mutations, halting DNA replication, and cell death.

What is the purpose of base-excision repair?

To correct point mutations by removing and replacing modified bases.

How does uracil in DNA get repaired?

Uracil DNA glycosylase recognizes and removes uracil to prevent CG base pairs from mutating to UA.

What is homologous recombination?

A process where two DNA molecules exchange genetic material, typically occurring to repair double-strand breaks.

What is a hallmark of many cancers regarding telomerase?

The reactivation of telomerase enables continued cell division despite telomere shortening.

What enzyme catalyzes the formation of phosphodiester linkages between DNA strands?

DNA ligase.

What two factors make eukaryotic DNA synthesis more complex than prokaryotic?

Larger genome size and more complex chromosome structure.