1. DNA REPLICATION and MUTATIONS

2. DNA Replication  Replication – the process of copying a DNA molecule.
So that genetic information can be passed on from cell to cell.
DNA replicates before cells divide (S phase)

3. Quick Review… DNA is made up of 2 strands of nucleotides.
The strands are held together by HYDROGEN BONDS between each of the bases.
The 2 strands are COMPLEMENTARY
A pairs with T
C pairs with G

4. 
How it Works
During replication EACH strand is used as a pattern (template) to make 2 new DNA molecules
This is called semi-conservative replication

5. Original RIGHT with new left strand
How it Works
AND
Original LEFT with
new right strand
Original RIGHT with new left strand
Original DNA

6. Steps in DNA Replication
Steps in DNA Replication
Double helix unwinds.
DNA helicase (an ENZYME) “unzips” the DNA molecule, breaking the hydrogen bonds between the strands
Unpaired
bases
DNA helicase
(enzyme)

7. Steps in DNA Replication
Steps in DNA Replication
DNA Polymerase (another ENZYME) pairs up free nucleotides in the nucleus with the nucleotides on the DNA strands forming new hydrogen bonds.
Where do nucleotides come from?
YOU ARE WHAT YOU EAT!

8. Steps in DNA Replication
Original
DNA
DNA
unzips
Free nucleotides pair up with the original LEFT strand
Free nucleotides pair up with the original RIGHT strand

9. Steps in DNA Replication
Steps in DNA Replication
The DNA winds back up into a double helix.
The final products of DNA replication are two molecules of DNA each having half new material and half old material… “Semi-conservative”

10. DNA Replication Original strand DNA polymerase New strand Growth
Replication fork
Replication fork
Nitrogenous bases
New strand
Original strand

11. 
Why Replicate?
Now all genetic information can be passed onto new cells during cell division.
2 new identical cells
DNA copied

12. Polymerase Chain Reaction (PCR)
Can be used to make millions of copies of a DNA sequence from a very small sample
Forensics, paternity testing, etc.
PCR Video

13. 
Accuracy
Replication is also very accurate – only ONE IN A BILLION base pairs are incorrectly paired.
When mistakes are made, the DNA molecule can correct itself so the genetic code remains the same.
Sometimes they can’t… MUTATIONS

14. GENE MUTATIONS (in DNA)
GENE MUTATIONS (in DNA)

15. Point Mutations Happen At Single Nucleotide Points in DNA
Point Mutations Happen At Single Nucleotide Points in DNA
Substitution
One base changes to (“subs” for) another
Insertion
Base added (inserted)
Deletion
Base removed (deleted)

16. Point Mutation – Deletion

17. The Dog Ate The Fat Cat Substitution Deletion Insertion
The Dog Ate The Fat Rat
Deletion
The Oga Tet Hef Atr At..
Insertion
The Dog Tat Eth Efa Tra t

18. What kind of point mutation?
SUBSTITUTION

19. What kinds of point mutation?
INSERTION
DELETION

20. Insertions and Deletions Can Cause FRAMESHIFTS in the code!
Insertions and Deletions Can Cause FRAMESHIFTS in the code! 
Uh Oh! One nucleotide affected every codon down the line—a frameshift!

21. Now: CHROMOSOMAL MUTATIONS (affect whole chromosomes)
Now: CHROMOSOMAL MUTATIONS (affect whole chromosomes)

22. What Would You Call It?
Deletion

23. One or more segment is repeated
What Would You Call It?
normal chromosome
one segment repeated
three repeats
Duplication
One or more segment is repeated

24. A linear stretch of DNA is reversed within the chromosome
What Would You Call It?
Inversion
A linear stretch of DNA is reversed within the chromosome

25. 
What Would You Call It?
chromosome
nonhomologous chromosome
reciprocal translocation
Translocation Entire gene segments are exchanged between non-homologous chromosomes!

26. Check Point

27. Mutations may be:  Silent or neutral (no effect)
Harmful or Fatal (bad effect)
Beneficial (good effect, low probability)