DNA

1. DNA What is DNA? Why is it important? Structure of DNA DNA Replication DNA Discoveries and Scientists Why is DNA important (again)

2. What is DNA? • DNA- deoxyribonucleic acid • DNA contains the genetic information that makes you, you… animals, animals and plants, plants… • DNA is composed of: • Double helix • Phosphate group • 5 carbon sugar (deoxyribose) • Nitrogen containing base • Weak hydrogen bonds Make up a Nucleotide

3. Why is DNA Important? • DNA is in all living things • It is found in the cytoplasm of bacteria and in the nucleus of protists, fungi, plants, and animals.

4. S P The Structure of DNA • Nucleotides- subunits that make up DNA • Phosphate group • 5 carbon sugar (deoxyribose) • Nitrogen containing base: • Adenine Thymine (A – T) • Guanine Cytosine (G – C) * Weak hydrogen bonds hold bases together

5. The Structure of DNA • Double helix- two strands of nucleotides twisted around each other, like a winding staircase • Complementary base pairs- the sequence of bases on one strand that determines the sequence of the other strand • Adenine Thymine • Cytosine Guanine

6. A T C G G C T A T A The Structure of DNA • So, if the sequence on one side is:

7. C A 5’ The Structure of DNA • Label: • Phosphate (P) • 5 carbon sugar • (S) • Correct base pairs • (A, T, C, G) • Draw hydrogen bonds 3’ 5’ 3’

8. The Structure of DNA *Note about bases: • Pyrimidines- single ring of carbon • Tymine and Cytosine • Purine- two rings of carbon • Adenine and Guanine A purine must always bond with a pyrimidine!

9. DNA Replication • DNA Replication- the process of making a copy of DNA • Why is this important? • Cells need to copy their DNA for mitosis (growth, repair, and maintenance) • Three steps: • Double helix unwinds and opens • DNA polymerases add nucleotides back • Polymerases detach once replication is complete

10. DNA Replication Step 1: • The double helix must unwind before replication can begin. • DNA helicases are enzymes that open the double helix by breaking the hydrogen bonds that hold the complimentary bases together (think of a zipper) • Replication goes from 5’ to 3’

11. DNA Replication Step 1 con’t: • Once separated, additional proteins hold the strands apart. • Where the double helix separates is called a replication fork (because of it’s Y shape)

12. DNA Replication Step 2: • At the replication fork enzymes called DNA polymerases move along each of the DNA strands. • DNA polymerases add nucleotides to the exposed bases according to the base pair rules

13. DNA Replication Step 3: • Step 2 continues until all DNA has been copied and the polymerases detach • Produces 2 DNA molecules that are identical to each other and the original strand

15. DNA Discoveries and Scientists • Alfred Hershey and Martha Chase- discovered that DNA stores genetic information in living cells • James Watson and Francis Crick- pieced together the structure of DNA • Chargaff- noticed the rules for base pairing (Adenine- Thymine and Cytosine – Guanine)

16. Why is DNA important? • DNA is the basis of genetic material and serves as the template for making proteins. • Proteins make: • your eye color and hair color • antibodies in your blood • enzymes vital to your metabolism • skin and muscles • Proteins make you, you!