Name one scientist who was
involved in the discovery of the
structure of the DNA molecule.
DNA replication
Before a cell can go through mitosis or meiosis, it’s DNA first must be
copied.
Replication
• The process of copying DNA. Occurs during
late interphase (during the S phase)
Replication
• Step 1:
DNA molecule separates into two strands
- enzymes called helicase “unzip” molecule of
DNA by breaking hydrogen bonds
DNA replication
• Step 2:
• Nucleotides are added to separated strands
of DNA.
• -The enzyme DNA polymerase joins individual
nucleotides to produce a new strand of DNA.
New nucleotides are added to separated strand by following base
pairing rules.
Nucleotides with nitrogen base A, pair with base T
base C pairs with base G
DNA replication
• Step 3:
As replication continues, the new strands
twist into their helical form.
DNA replication enzymes
DNA helicase
an enzyme that unwinds and separates the
two strands of the DNA double helix.
• DNA polymerase
• Two functions:
•
1. Attaches nucleotides to DNA strand
•
2. Proofreads each new DNA strand
Prokaryotic DNA replication
• Prokaryotic DNA is found in the cytoplasm.
Most have a single, circular DNA molecule
• Replication in most prokaryotic cells starts
from a single point and proceeds in two
directions until the entire chromosome is
copied
Eukaryotic DNA replication
• Replication may begin at dozens or even
hundreds of places on the DNA molecule,
proceeding in both directions until each
chromosome is completely copied.
https://www.youtube.com/watch?feature=playe
r_detailpage&v=HBwyNrkYnp0
https://www.youtube.com/watch?feature=pla
yer_detailpage&v=zdDkiRw1PdU
Telomeres
• The tips of chromosomes that make it less
likely that important genes will be lost during
replication.
Telomeres
• The tips of chromosomes that make it less
likely important genes will be lost during
replication.
What is the name of the enzyme
that adds new nucleotides to the
separated DNA strand?
• DNA polymerase
1. What is the name of the process in
which DNA makes a copy of itself?
2. What type of bond forms between
two nitrogenous bases?