Unit 3: Molecular Genetics Section1-DNA and RNA

I. Ancient Ideas a. Hippocrates suggested traits passed through pangenes- any alterations made to self passed to offspring b. Blending hypothesis- the cells from mother and father blended together to make offspring. c. Proteins were hereditary material a. Proteins are not passed from parent to offspring b. What carried the genetic information?

II. Discoveries a Frederick Griffith a. Used 2 strains of bacteria a. S strain- not killed by immune system b. R strain-killed by immune system b. Infected mice using both strains c. Killed the S strain and injected it with R strain- mice died d. Conclusion- Something in the S strain was transferred to the R strain that allowed it to kill the mouse b Oswald Avery- confirmed that DNA was the molecule transferred.

II. Discoveries c Alfred Hershey and Martha Chase a. Used radioactive viruses to show that DNA was being transferred to the cell, not protein. d Erwin Chargaff a. Determined the composition of DNA a. The amount of thymine=amount of adenine b. The amount of guanine=amount of cytosine b. DNA is different in different species

II. Discoveries e Rosalind Franklin a. Used X-ray diffraction to determine that DNA was a double helix b. Died from ovarian cancer f James Watson and Francis Crick a. Published structure of DNA- won Nobel Prize

III. Structure of DNA a. Deoxyribonucleic Acid b. Building block of DNA-Nucleotide a. Deoxyribose sugar b. Phosphate c. Nitrogenous Base

IV. DNA a. Sugar-phosphate backbone a. Alternating deoxyribose sugar and phosphate molecules-Covalent bonds b. Nitrogenous bases a. Attached to sugars b. Purines- two ring molecules a. Adenine and Guanine c. Pyrimidines- one ring molecules a. Thymine and Cytosine c. Double Helix a. Two strands wind around each other in opposite directions (anti-parallel)-held together by hydrogen bonds Adenine-Thymine Guanine-Cytosine

V. RNA a. Single stranded molecule that transfers genetic code to ribosomes where proteins are made b. Differences from DNA a. Uses uracil instead of thymine b. Uses ribose sugar c. Small d. Moves from nucleus to cytoplasm