BIOL 4426: Cellular Physiology ch4

This set of flashcards covers key concepts related to cellular physiology, specifically focusing on DNA replication, repair mechanisms, and the cell cycle.

What is the key characteristic of chromosome replication as demonstrated by the Messelson-Stahl experiment?

Replication is semiconservative; a new strand is synthesized alongside the old template strand.

What type of replication process occurs in both prokaryotic and eukaryotic cells?

Replication is bidirectional, involving replication forks.

What marks the specific locations at which DNA replication begins?

Origins of replication, recognized by the Origin Recognition Complex (ORC).

How many origins of replication do most eukaryotic cells have compared to prokaryotic cells?

Eukaryotic cells have approximately 10,000-100,000 origins of replication, while prokaryotic cells usually have a single origin.

What is the estimated rate of DNA replication at each fork in mammalian cells?

Approximately 100 nucleotides per second.

What is the role of helicase in DNA replication?

Helicase unwinds the DNA double helix at the origin of replication.

What is the significance of Primase in the DNA replication process?

Primase synthesizes RNA primers needed to initiate DNA synthesis.

What is the function of DNA ligase during replication?

DNA ligase joins Okazaki fragments on the lagging strand and seals repaired DNA.

What do topoisomerases do during DNA replication?

Topoisomerases relieve the tension created by unwinding the DNA strands.

How do telomeres protect eukaryotic chromosomes during replication?

Telomeres prevent the loss of genes by adding repetitive sequences at the ends of linear chromosomes.

What is the main purpose of the end-joining repair system in DNA repair?

It repairs double strand breaks, though repairs may lead to mutations.

What is homologous recombination?

A DNA repair pathway that allows for the exchange of homologous DNA sequences.

What is the role of RecA in bacterial homologous recombination?

RecA mediates strand invasion and alignment during the recombination process.

How does the cell cycle integrate DNA replication?

Replication occurs during the S phase of the cell cycle, with preparation occurring in the G1 phase.

What is the role of Cyclin-Dependent Kinases (CDKs) in the cell cycle?

CDKs regulate cell cycle checkpoints and transitions between phases.

What can cause excessive DNA damage leading to cell death?

Environmental factors like radiation and chemical mutagens can cause significant DNA damage.

What does the mismatch repair system specifically correct?

It corrects single base pair mismatches during DNA replication.