Unit 3: Molecular GeneticsSection1-DNA and RNA

I. Ancient Ideasa. 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 materiala. Proteins are not passed from parent to offspringb. What carried the genetic information?

II. Discoveries

a. 1928 Frederick Griffitha. Used 2 strains of bacteria

a. S strain- not killed by immune systemb. R strain-killed by immune system

b. Infected mice using both strainsc. Killed the S strain and injected it with R strain-

mice diedd. Conclusion- Something in the S strain was

transferred to the R strain that allowed it to kill the mouse

b. 1944 Oswald Avery- confirmed that DNA was the molecule transferred.

II. Discoveries

c. 1952 Alfred Hershey and Martha Chasea. Used radioactive viruses to show that DNA was

being transferred to the cell, not protein.

d. 1947 Erwin Chargaff a. Determined the composition of DNA

a. The amount of thymine=amount of adenineb. The amount of guanine=amount of cytosine

b. DNA is different in different species

II. Discoveries

e. 1950 Rosalind Franklina. Used X-ray diffraction to determine that DNA

was a double helixb. Died from ovarian cancer

f. 1953 James Watson and Francis Cricka. Published structure of DNA- won Nobel Prize

III. Structure of DNA

a. Deoxyribonucleic Acidb. Building block of DNA-Nucleotide

a. Deoxyribose sugarb. Phosphatec. Nitrogenous Base

IV. DNA

a. Sugar-phosphate backbonea. Alternating deoxyribose sugar and phosphate

molecules-Covalent bonds

b. Nitrogenous basesa. Attached to sugarsb. Purines- two ring molecules

a. Adenine and Guanine

c. Pyrimidines- one ring moleculesa. Thymine and Cytosine

c. Double Helixa. 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 DNAa. Uses uracil instead of thymineb. Uses ribose sugarc. Smalld. Moves from nucleus to cytoplasm