DNA and Replication

1. DNA and Replication Test: Friday Nov. 19 Covers Viruses and DNA/Replication

2. DNA- Deoxyribonucleic Acid • DNA codes for genes which carry your genetic information.

3. History of DNA • 1953 • Watson and Crick proposed the double helix, or spiral staircase, structure of the DNA molecule • They were awarded the Nobel prize for this discovery

4. DNA Discovery • The Hershey-Chase Experiment • Bacteriophages: a virus that attacks bacterial cells. They inject genetic material and take over the cell • Radioactive markers: tag and stick to certain parts of the bacteriophage

5. Hershey-Chase Experiment-pg290 Bacteriophage with phosphorus-32 in DNA Phage infectsbacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infectsbacterium No radioactivity inside bacterium

6. Hershey-Chase Experiment-pg290 Bacteriophage with phosphorus-32 in DNA Phage infectsbacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infectsbacterium No radioactivity inside bacterium

7. Hershey-Chase Experiment-pg290 Bacteriophage with phosphorus-32 in DNA Phage infectsbacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infectsbacterium No radioactivity inside bacterium

8. Structure of DNA Chargaff’s Rules *base pairing rule of A+T & C + G Source of DNA A T G C Streptococcus 29.8% 31.6% 20.5% 18.0% Yeast 31.3% 32.9% 18.7% 17.1% Herring 27.8% 27.5% 22.2% 22.6% Human 30.9% 29.4% 19.9% 19.8%

9. X-Ray Evidence of DNA • Rosalind Franklin • Suggested a twisted double helix

10. DNA Structure • DNA structure is made up of nucleotides • Each nucleotide is made up of three parts: • Sugar (deoxyribose) • Phosphate • Nitrogenous Base • (Adenine, Thymine, Guanine, Cytosine)

11. Structure of DNA Nucleotide (3 parts) Hydrogen bonds (connect bases) Sugar/phosphate Backbone (sides) Key Adenine Thymine Cytosine Guanine Deoxyribose sugar is attached to all bases

12. Base-Pair Rule • In a DNA molecule bases pair up in predictable ways • Adenine always pairs with Thymine • Guanine always pairs with Cytosine • A = T • G = C

13. Base Pair Rule One side:     A   T   A      T   C   A      T   G   C      G   GG Other side:

14. How the Code Works The combination of A,T,G,C determines what traits you might have, for ex. C A T C A T   =  purple hair T A C T A C  =  yellow hair

15. Think of the bases of DNA like letters.Letters form words....Words form sentences....              *endless               combinations

16. All the activities of the cell are controlled by DNA. DNA is located in the nucleus of the cell. Just before cell division DNA coils to form chromosomes. A Chromosome is tightly coiled DNA. When a chromosome is unraveled, it reveals DNA’s double helix shape.

17. DNA Replication • When a cell divides each cell needs its own DNA • DNA must replicate and produce two identical strands of DNA in order for this to happen

18. Process of DNA Replication • An enzyme “unzips” the existing DNA strand • Free floating nucleotides attach themselves to each side • TWO new strands of DNA are formed for each new cell

19. This “double helix structure” makes it possible for DNA to make an exact copy of itself. T T T T T T T T A A A A A A A A A A A A A A A A T T T T T T T T G G G G G G G G G G C C C C C C C C C C C C C C C C C C G G G G G G G G 1 DNA “unzips itself.” 2 Free-floating nucleotides attach themselves to each side. DNAPolymerase This is known as replication.

20. DNA Replication Video http://www.youtube.com/watch?v=hfZ8o9D1tus

21. DNA Fingerprinting • The only difference between your DNA and the DNA of the person sitting next to you is the order of the DNA base pairs • Every person has a different sequence • DNA fingerprinting is a way to identify and distinguish among individual human beings

22. Who did it???

23. Who did it???

24. Comparing DNA Fingerprints