DNA Replication Notes

This is information that you need to know for state testing.

1. DNA Replication NotesDNA Replication Notes

2. DNA ReplicationDNA Replication
Replication of DNA:Replication of DNA:
DNA unwinds and DNA unwinds and
each strand serves as each strand serves as
a template for new a template for new
DNA.DNA.
This means you will This means you will
have 2 copies of the have 2 copies of the
same DNA after same DNA after
replication.replication.

3. DNA ReplicationDNA Replication
HelicaseHelicase: is the enzyme that unwinds (breaks : is the enzyme that unwinds (breaks
bonds) and separates the two strands of DNA.bonds) and separates the two strands of DNA.
Helicase breaks the hydrogen bonds that were Helicase breaks the hydrogen bonds that were
hold the two nitrogen bases together.hold the two nitrogen bases together.

4. DNA ReplicationDNA Replication
DNA polymeraseDNA polymerase: enzyme that adds nucleotides : enzyme that adds nucleotides
to each strand of DNA.to each strand of DNA.
Many polymerases attach at the same time.Many polymerases attach at the same time.

On a fruit fly DNA replication starts at 6,000 different On a fruit fly DNA replication starts at 6,000 different
placesplaces

6. DNA ReplicationDNA Replication
According to the base pairing rules, what According to the base pairing rules, what
would the new stand of DNA be if the would the new stand of DNA be if the
original strand was:original strand was:
A – T – T – C – C- G A – T – T – C – C- G
New strand would be:New strand would be:
T – A – A – G – G – C T – A – A – G – G – C

7. DNA ReplicationDNA Replication
Accuracy and RepairAccuracy and Repair
DNA is copied with a high degree of DNA is copied with a high degree of
accuracy, there are enzymes that proof accuracy, there are enzymes that proof
read DNA while its being replicated.read DNA while its being replicated.

8. DNA ReplicationDNA Replication
MutationMutation: change in the nucleotide : change in the nucleotide
sequence of DNA; it can have serious sequence of DNA; it can have serious
effects on the organism.effects on the organism.

Can be harmful or beneficialCan be harmful or beneficial

9. DNA ReplicationDNA Replication
Environmental factors Environmental factors
can damage DNAcan damage DNA

Ex. Ultraviolet Ex. Ultraviolet
radiation from the sun, radiation from the sun,
enzymes in the cell enzymes in the cell
work to repair the work to repair the
damaged DNA.damaged DNA.

Without repair Without repair
enzymes, mutations enzymes, mutations
would occur more would occur more
often and cells would often and cells would
die easier.die easier.

10. DNA ReplicationDNA Replication
Environmental factors Environmental factors
can damage DNAcan damage DNA

Ex. Ultraviolet Ex. Ultraviolet
radiation from the sun, radiation from the sun,
enzymes in the cell enzymes in the cell
work to repair the work to repair the
damaged DNA.damaged DNA.

Without repair Without repair
enzymes, mutations enzymes, mutations
would occur more would occur more
often and cells would often and cells would
die easier.die easier.