Download DNA Replication

What will you learn?
DNA Replication
PLO
B5
B6
It is expected that students
will…
describe DNA replication
describe recombinant DNA
DNA is composed of units called NUCLEOTIDES, which are composed of three
sub-molecules:
1. Pentose Sugar (deoxyribose)
2. Phosphate
3. Nitrogen Base (purine or pyrimidine)
DNA (Deoxyribonucleic Acid)
DNA Structure
p. 508
DNA
Functions:
• stores genetic information and copies
itself (replication) to pass on the
information
• contains genes (instructions to make
proteins)
• DNA instructs cell’s activities
PYRIMIDINES = T & C
PURINES = A & G
Complimentary Base Pairing
Nucleotide Bases
(Only copy chart, not structures)
PURINES
PYRIMIDINES
Double N-ring
Single N-ring
A&G
C & T/U
# of purines always equals the number of pyrimidines
DNA is composed of two
complimentary strands of nucleotides
joined by hydrogen bonds:
Adenine with Thymine (A-T or T-A)
They join with 2 hydrogen bonds
Cytosine with Guanine (C-G or G-C)
They join with 3 hydrogen bonds
DNA twists into a double helix
http://www.biostudio.com/demo_freeman_dna_coiling.htm
DNA Structure
Chromatin = DNA
strand + proteins
wrapped abound the
DNA
Chromosome =
condensed
chromatin
Nucleotide
sugar, phosphate, nitrogenous base
Hierarchy of
DNA
DNA
polymer of nucleotides
Chromatin
DNA strand
A gene is a section
of a chromosome
that codes for a
protein
proteins (histones)
Chromosomes
condensed, coiled chromatin
Genome
full set of genetic information within a species
Chromosomal
structure
Cell Cycle
DNA Replication
• Before cells divide, a
complete copy of their
DNA (DNA replication)
must be made
• Occurs in the nucleus
Steps of DNA Replication
http://www.youtube.com/watch?v=zdDkiRw1PdU
Step 1: Unzipping
–
–
DNA strand unwinds
helicase (enzyme) breaks H-bonds
between N-bases →→ “unzipping”
Steps of DNA Replication
Step 2. Complementary base pairing
–
DNA nucleotides move into position to
bond with their partners on the DNA
strands (“the templates” or “the parent
strands”)
Step 3: Joining of adjacent nucleotides
– 2 new sugar-phosphate backbone forms
when enzyme, DNA polymerase, forms
covalent bonds between new nucleotides.
End up with 2 identical DNA strands which
are semi-conservative (composed the
original “parent” and a new “daughter”
strand)
FYI: DNA replication occurs about 100 nucleotides per sec
Semi-conservative
Step 4: Proof reading
– DNA polymerase also checks for mistakes
(mutations)
Huh?
• Watch this....
http://highered.mcgrawhill.com/sites/dl/free/0072421975/196646/l
w09_dna_replication_final.html