chromosome gene dna so when a cell divides, the new cells have a complete set of dna instructions
TRANSCRIPT
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DNA Replication
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Review DNA Hierarchy
Chromosome
Gene
DNA
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Why does DNA need to replicate?Hint: Think about our cell division activity.
So when a cell divides, the new cells have a complete set of DNA instructions.
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Let’s quickly review DNA structure in prokaryotes and eukaryotes.
PROKARYOTES Double stranded Single ring Found in cytoplasm A-T C-G
EUKARYOTES Double stranded Double helix Found in nucleus A-T C-G
Nucleotide
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From the videos, what differences did you see in the replication of DNA in prokaryotes vs. eukaryotes?
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DNA Strands are Antiparallel
DNA is read 5’ to 3’
Strand on the left 5’ TTCAGT 3’
Strand on the right 5’ ACTGAA 3’
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Replication of DNA
PROKARYOTES
Begins at a single point in the chromosome
Proceeds in two directions until the entire chromosome is separated
EUKARYOTES
Replication can be occurring at hundreds of places along the same DNA strand
vs
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How does DNA replicate?
What has to happen to the DNA strand first?
Double stranded DNA must be separated!How does this happen?
An enzyme called DNA
Helicase breaks the hydrogen
bonds between the strands!
Enzymes help the double strand unwind
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Once strands are separated and unwound, what happens?
NucleotideDNA Polymerase adds
free nucleotides that pair up to the exposed original strand (using Base Pairing Rules!!!)
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DNA polymerase binds the free nucleotides to the original strand.
DNA Polymerase
DNA polymerase also checks for errors.
It can only add nucleotides if the previous nucleotide is correctly paired. If there is an error, it backtracks to make the correction.
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DNA Replication is Semi-Conservative
During replication, existing DNA strands serve as templates for new complementary strands
Parent (original) strand present in all daughter (new) strands
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Complementary Base Pairing Practice
Remember -- A-T C-G
5’ 3’ 5’ 3’ ATGGCGTCATGCTTAGATTA3’ 5’
TACCGCAGTA
3’ 5’
CGAATCTAAT