DNA Replication and Telomeres

A collection of flashcards covering key concepts from the lecture on DNA replication and telomeres.

What important process is described by the term 'semi-conservative' in DNA replication?

It refers to the mechanism where each new DNA strand is composed of one parental strand and one new strand.

What is the primary function of DNA polymerases during replication?

DNA polymerases replicate DNA by synthesizing new DNA strands in the 5' to 3' direction.

What experiment did Meselson and Stahl conduct to demonstrate the nature of DNA replication?

They used different nitrogen isotopes to trace DNA replication in E. coli, demonstrating it was semi-conservative.

What bonds are formed during DNA replication between nucleotides?

Phosphodiester bonds are formed between the sugar of one nucleotide and the phosphate of another.

What is the role of primase in DNA replication?

Primase synthesizes a short RNA primer that provides a 3'-OH group for DNA polymerases to initiate synthesis.

Why do Okazaki fragments occur during DNA replication?

They occur because DNA replication is discontinuous on the lagging strand, requiring multiple short segments to be synthesized.

What is the role of helicase in DNA replication?

Helicase unwinds the DNA double helix, separating the two strands to allow replication.

What is the significance of single-stranded DNA binding proteins (SSB)?

SSBs protect single-stranded DNA during replication and prevent it from re-forming into a double helix.

How do telomeres maintain the integrity of linear chromosomes?

Telomeres protect the ends of chromosomes from degradation and prevent fusion with neighboring chromosomes.

What happens to telomeres with each cell division?

Telomeres shorten with each cell division due to incomplete replication of the 3' ends of linear chromosomes.

What are G-quartets and why are they important in telomere structure?

G-quartets are structures formed by guanine-rich sequences that help stabilize single-stranded DNA at telomeres.

What is TRF2 and its role in telomere maintenance?

TRF2 is a telomere repeat binding factor that catalyzes the looping of telomeres to protect chromosomal ends.

What are the two types of topoisomerases and their functions?

Type I introduces single-strand breaks; Type II introduces double-strand breaks to relieve supercoiling during replication.

How do eukaryotic origins of replication differ from prokaryotic origins?

Eukaryotes typically have multiple origins of replication, while prokaryotes usually have a single origin.

What kind of replication occurs at replication forks?

Replication can be uni- or bidirectional at replication forks, allowing simultaneous synthesis from a common origin.

What signifies the presence of Okazaki fragments in a DNA strand?

The lagging strand synthesis forms Okazaki fragments due to the discontinuous nature of replication.

How are Okazaki fragments processed after synthesis?

They are joined by DNA ligase after RNA primers are removed and replaced by DNA.

What is the challenge posed by the ends of linear chromosomes during replication?

The challenge is that DNA polymerases cannot fully replicate the end of linear chromosomes, leading to shortening.

What is a replicon?

A replicon is a region of DNA or RNA that replicates from a single origin of replication.

How does helicase activity consume energy during DNA replication?

Helicases utilize ATP hydrolysis to unwind the DNA strands.