Page 14 - CB1.3 Genetic Varation sciPAD

PHOTOCOPYING PROHIBITED
© Silverback Academic Media
14 CB 1.3 GENETIC VARIATION
PRINCIPLES OF GENETIC VARIATION
DNA Replication
To ensure that every new cell has its own complete copy of the genetic code, DNA must be
copied (replicated) before a cell divides.
1. Does DNA replication occur before, during or after cell division? 
2. Describe the purpose of DNA replication. 

3. Summarise the key processes involved in DNA replication. 






4. Explain why DNA replication is known as ‘semi-conservative replication’
. 



Dire ctio n
o f r e
p
li c
a
t i
o
n
D ir e c t i o n
o f r e
p l i c
a
t i
o
n
At the end of the process,
two new molecules of DNA
are produced. Both are
exact copies of the original
molecule. Each winds up
forming a helix.
1
2
4
3
It is called
‘semi-conservative replication’.
This is because one half of the
new DNA molecule is an intact
strand from the old DNA.
An enzyme unwinds the parent DNA strand by
breaking the hydrogen bonds between bases.
This exposes the base pairs.
Enzymes bond the
nucleotides together
to form the new
strand.
Enzyme
New nucleotides are
brought in. They bond with
the bases on the parent
DNA molecule, according
to the complementary
base-pairing rules.
Enzyme
Unchecked Sample Pages
For Review Purposes Only - Photocopying Prohibited
www.scipad.co.nz