2. DNA: deoxyribonucleic acid DNA history, structure, replication, and gene expression (transcription, translation, protein synthesis)

3. DNA: the basics Double helix (twisted ladder, double spiral) Chromosomes are made of it (46) Genes are made of it (25,000 or so) Each gene is the code for a protein DNA is the genetic code, a chemical blueprint to create an organism Made of nucleotides: sugar, phosphate, base

4. What are bases? Bases form the code for information in DNA Four bases: cytosine, guanine, adenine, thymine (CGAT) –Four bases means there are 4 nucleotides –Four bases means there are 4 symbols in the code. Base pairing rule –adenine always bonds with thymine (AT) –Guanine always bonds with cytosine (CG)

6. History of DNA People thought proteins must be the genetic code because there are lots of them 1928: Griffith “transformation” experiment showed that genes were not alive (protein or DNA?) 1940: Chromosomes made of DNA –Genes made of protein or DNA? 1944: Avery shows DNA was genetic material in Griffith’s experiment 1952: Hershey and Chase “bacteriophage” experiment showed DNA was genetic material. 1947: Chargaff discovered base pairing rule

7. The heroes of DNA 1952: Rosilind Franklin made x-ray photo of DNA crystal. Showed it was a helix shape. 1953: Watson and Crick –Proved DNA was a double helix –Bases are the “letters” in the code –Explained replication

8. Rosalind Franklin (in Paris)

10. Watson and Crick 1953 article in Nature CrickWatson

11. DNA replication: copying DNA An enzyme unzips the helix--”helicase” Nucleotides move in--bases must “compliment” Each half forms a “complimentary” strand replacing the missing half. An enzyme controls this--”polymerase”

12. Protein Synthesis Genes are for making proteins. Step one –Transcription: make a copy of the gene with mRNA. The enzyme RNA polymerase controls this. Also, there’s a promoter or start “gene” and there are stop “genes” send the the messenger RNA out of the nucleus to the ribosomes Step two –Translation The ribosome uses the order of the nucleotide bases to line up amino acids in the right order to make the protein tRNA (transfer RNA) brings the amino acids to the ribosome Remember: proteins are long chains of amino acids. mRNA gene copy has the code for the order of the amino acids. Ribosomes make proteins.

13. RNA is different RNA is a single helix RNA has ribose instead of deoxyribose RNA has uricil instead of thymine!!! 3 flavors of RNA: mRNA, tRNA, and rRNA Copying the gene follows base pairing rule just like DNA replication. Making DNA –DNA: CGATTAGC –DNA copy: GCTAATCG Making RNA –DNA: CGATTAGC –mRNA: GCUAAUCG (notice U goes where T should be!!!)

14. The genetic code 3 mRNA bases = codon (complimentary to DNA codon) 1 codon = 1 amino acid tRNA has an anticodon that is the compliment to the codon Like this –DNA CGA TTA GCA –mRNA GCU AAU CGU codons –tRNACGA UUA GCA anticodons How do you know which amino acids are used? –Use the “Punnett square” for genes –Notice the stop codons!! (UUA, UAG, UGA)

15. proteinRNA The “Central Dogma” DNA transcriptiontranslation replication Flow of genetic information in a cell

16. Final note on transcription of mRNA Exon: the part of the DNA that is part of the gene Intron: part of the DNA that is not part fo the gene! “Introduced” by viruses and stuff The introns have to be removed to make the mRNA.

17. MUTATIONS: most are recessive Types –Point: change one base –Point shift: change the order –Deletion –Inversion –Insertion Dominant mutations include dwarfism and Huntington’s disease

18. Mutations and cancer Cancer: mitosis out of control Carcinogen--chemicals and stuff like radiation and UV light that cause cancer-- damage or change DNA! Mutagens--things that cause mutations in genes. Somatic or body cell mutations cause cancer. Germ cell (gametes) mutations cause birth defects.

19. Cancer: mutations in somatic cells Benign tumors don’t spread Malignant tumors spread to other parts of the body to cause new tumors Metastasize: when cancer spreads Chemotherapy--chemicals that treat cancer usually interfere with mitosis

20. Sickle Cell Anemia Genetic Disease Heterozygous individuals – carriers Homozygous individuals – diseased Hemoglobin Found in red blood cells Carries oxygen to tissues SCA Results from Defective Hemoglobin Hemoglobins stick together Red blood cells damaged Complications from low oxygen supply to tissues Pain, organ damage, strokes, increased infections, etc. Incidence highest among Africans and Indians Heterozygotes protected from Malaria

21. GENE TECHNOLOGY Human Genome Project: –map all our genes –Other genomes have been mapped, too. Stem cell therapy Genetic engineering/recombinant DNA: –Bacteria given a human gene to make insulin –GMO: genetically modified organisms (corn with a bacteria gene for a pesticide). “frankinfood” –Glowing genes from jellyfish or lightning bugs to track genes Gene therapy: use viruses to replace bad genes Forensics (CSI) –Genetic/DNA fingerprinting uses electrophoresis Genetic tools –Restriction enzymes: cut DNA up –PCR: duplicates DNA