12.2-Chromosomes and DNA Replication

Why do chromosomes need to be folded and packed?

If unwrapped, they are much longer than organism itself.

First step of DNA replication

Helicase "unzips" DNA

What direction are the two strands of DNA in?

Antiparallel

Second step of DNA replication?

Primase places RNA primers that polymerase can then latch onto.

Third step of DNA replication?

New strands of copied DNA are created.

What happens to the RNA primers in the end of DNA replication?

Removed and replaced with DNA

Other than replicating DNA, what does polymerase also do?

It proofreads the duplicated DNA

Why is DNA replication considered "semi-conservative?"

Because the two daughter DNA contain one strand from the parent and the other strand that is duplicated from the parent.

In what direction is DNA replicated? (think carbon numbering)

From 5' to 3'.

What is the leading strand?

The DNA that is being replicated in the same direction as helicase is unzipping the DNA. (moving away from the replication fork)

What is the lagging strand?

The DNA that is being replicated in the opposite direction as helicase is unzipping the DNA. (moving away from replication fork)

What is the lagging strand made of?

Okazaki fragments

What does ligase do

Joins the Okazaki fragments back together

Why is there a lagging strand?

Because DNA is antiparallel.

What carbon number label is the sugar in nucleotides?

3'

What carbon number label is the phosphate in nucleotides?

5'

What does primase do?

Creates RNA primer that polymerase can then latch onto

What does polymerase do?

Copy DNA by making nucleotides with complementary bases and proofreads duplicated DNA

What does ligase do?

Joins Okazaki fragments

What does helicase do?

Unzips DNA