1. DNA
CH 9

2. DNA
D= Deoxyribose Sugar
NA= Nucleic Acid
DEOXYRIBONUCLEIC ACID

3. DNA
The material that contains information that determines inherited characteristics

4. DNA
Shaped like a double helix
A spiral staircase structure

8. NUCLEOTIDES DNA is made of repeating subunits called nucleotides
Contain 3 parts
1. Phosphate
2. Sugar (deoxyribose)
3. Base (A,T,G,C)
Held together by hydrogen bonds

9. Nitrogen Bases
Adenine
Thymine
Cytosine
Guanine

10. Nitrogen bases
Purines: double ring
Pyrimidine: Single ring

11. Nitrogen bases Purines = Adenine and Guanine
Pyrimidine = Thymine and Cytosine

12. BASE PAIRING
One purine always pairs up with one pyrimidine

13. BASE PAIRING One purine always pairs up with one pyrimidine
Adenine pairs with Thymine
Guanine pairs with Cytosine

15. EXAMPLE
TATGGAGAGTC
ATA

16. EXAMPLE
TATGGAGAGTC
ATACCT

17. EXAMPLE
TATGGAGAGTC
ATACCTCTC

18. EXAMPLE
TATGGAGAGTC ATACCTCTCAG

19. DNA REPLICATION The process of making a copy of DNA
Occurs during the synthesis (S) phase of the cell cycle

20. Why is Replication Important?
It provides copies of genetic material for the new cell
If replication did not take place, the new cells would have half as much DNA as the parent cell

21. REPLICATION STEPS 1. Double helix unwinds
Hydrogen bonds are broken by enzymes called DNA helicases
The areas where the double helix separates are called replication forks

22. REPLICATION STEPS 2. Nucleotides are added
DNA polymerase (enzyme) moves along each strand of DNA at the replication fork
DNA polymerase add the nucleotides to the nitrogen bases according to the base pair ruling
Two new double helixes are formed

23. REPLICATION STEPS 3. New strands are formed
DNA polymerase continues working until the DNA has been copied and its is signaled to stop
Two DNA strands are produced which include an original and a new strand
The nucleotide sequences are identical to each other and to the original DNA molecule

26. CHECKING FOR ERRORS DNA polymerases “proof read” the new strands
If there is a mistake, the DNA polymerase backtracks and removes the incorrect nucleotide
A correct nucleotide is then added

27. Rate of Replication
If there were only one replication fork in eukaryotic cells, it would take 33 days to copy the DNA strand
Human chromosomes are replicated in about 100 sections
An entire Human chromosome can be replicated in about 8 hours