Transcript DNA replication - Sonoma Valley High School

Chromosomes and DNA replication
Procaryotes:
DNA is in the cytoplasm, circular
Chromosome
E. Coli Bacterium
Bases on the
Chromosomes
Eucaryotes
• DNA has 1000 X
the base pairs as
bacteria.
• Located in the cell
nucleus, on
chromosomes
• Folds into a space
1/1000th of its length
by wrapping around
the protein histone.
– Eukaryotic Chromosome Structure
Chromosome
me
DNA
Coils
Su
Nucleosome: DNA wrapped around a histone
DNA replication
• DNA molecule
separates
• Each side acts
as a template to
make a
complimentary
new strand.
• 1 molecule
becomes 2
DNA replication cont’d
• Enzymes “unzip”
the molecule and it
uncoils.
• New N bases come
in and bond to each
side.
• Polymerase joins
them into a new
molecule.
• It also “proofreads”
the new strands for
errors.
DNA Replication
New Strand
Original strand
Nitrogen Bases
Replication Fork
Replication Fork
DNA Polymerase
Summary
• One DNA strand
becomes 2 identical
strands, following the
rules of base pairing.
• Occurs at hundreds of
sites along the
chromosome at the
same time.