DNA Replication Overview

These flashcards cover essential vocabulary related to DNA replication, including key enzymes, processes, and concepts.

What does 'replicate' mean in DNA replication?

To make an exact copy of DNA, producing two daughter DNA molecules.

What are the two main things involved in DNA replication?

The parent/template DNA and many proteins/enzymes.

What is the end result of DNA replication?

Two daughter DNA molecules, each with one parent strand and one new strand (semi-conservative).

What does semi-conservative replication mean?

Each new DNA double helix contains one original strand and one newly synthesized strand.

What is the elongation rate in bacteria?

About 500 nucleotides per second.

What is the elongation rate in humans?

About 50 nucleotides per second.

How can the human genome replicate quickly despite a slow polymerase rate?

Multiple origins of replication operate simultaneously.

Name key characteristics of DNA replication.

Speedy, bidirectional, accurate (proofreading), and enzyme-dependent.

Where is prokaryotic DNA located?

In an unenveloped nucleoid region.

What is the shape of prokaryotic DNA?

Circular (closed).

Do prokaryotes have membrane-bound organelles?

No.

Where is eukaryotic DNA located?

Inside an enveloped nucleus.

What is the shape of eukaryotic DNA?

Linear chromosomes.

Why do eukaryotes need multiple origins of replication?

To replicate large genomes efficiently and quickly.

What are the three stages of DNA replication?

Initiation, elongation, termination.

What forms during initiation?

A replication bubble.

What are origins of replication?

Sites where DNA strands separate and replication begins; each origin forms two forks.

How many origins of replication do prokaryotes usually have?

Usually one.

Why is replication bidirectional?

Each origin produces two forks moving in opposite directions to speed replication.

How long is the E. coli origin of replication (oriC)?

About 250 base pairs.

Why is an AT-rich region important at oriC?

AT pairs separate more easily, helping the DNA open.

What are DnaA boxes?

Binding sites for initiator proteins that help start replication.

What is the role of GATC sequences at oriC?

They must be fully methylated for replication to begin.

What does hemimethylated mean?

Only one DNA strand is methylated after replication.

Why is delayed methylation useful?

It allows time for DNA repair before another replication cycle.

What enzyme unwinds DNA at the replication fork?

Helicase.

What do single-strand binding (SSB) proteins do?

They stabilize single-stranded DNA.

Why are topoisomerases important during replication?

They relieve supercoiling by cutting and rejoining DNA.

DNA gyrase is an example of what enzyme?

A topoisomerase.

Which polymerase is the main DNA builder in prokaryotes?

DNA polymerase III.

Why does DNA polymerase need a primer?

It requires a free 3' OH group to begin synthesis.

What enzyme makes the primer in prokaryotes?

Primase.

What type of nucleic acid is the primer?

RNA.

What is the function of the sliding clamp?

It keeps DNA polymerase attached to DNA for efficient synthesis.

What is the function of the clamp loader?

It loads the sliding clamp onto DNA using ATP.

What is the sliding clamp called in eukaryotes?

PCNA.

What is the clamp loader called in eukaryotes?

RFC.

In what direction does DNA elongation occur?

5' to 3'.

What defines the leading strand?

It is synthesized continuously toward the replication fork.

What defines the lagging strand?

It is synthesized discontinuously away from the replication fork.

What are Okazaki fragments?

Short DNA fragments formed on the lagging strand.

What enzyme joins Okazaki fragments?

DNA ligase.

What removes RNA primers in prokaryotes?

DNA polymerase I.

What are Ter sites in E. coli?

Termination sequences where replication stops.

What protein binds Ter sites to stop replication?

Tus.

How does the Ter-Tus complex stop replication?

It blocks helicase so replication machinery falls off.

What is proofreading in DNA replication?

Mechanisms that detect and correct mismatches.

Name causes of mutations listed in the lecture.

X-rays, smoking, carcinogens, spontaneous errors.

Which polymerase is mostly used on the leading strand in eukaryotes?

DNA polymerase ε (epsilon).

Which polymerase is mostly used on the lagging strand in eukaryotes?

DNA polymerase δ (delta).