BIS 101 Lect. 1 - Discovery of Genetic Material

Fall 26 Comai

Transformation

Uptake of naked DNA (or RNA) into a cell

Common in bacteria

Describe the bacteriophage experiment along with who discovered it

Hershey used radioactive Phosphorus and Sulfur 2 separate phages.

Phosphorus represented DNA while Sulfur represented Protein.

Found the Phosphorus in bacteria from bacteriophage = DNA is genetic material

Describe the discovery of RNA as genetic material

Frankel Conrat & Singer

RNA and protein were separated from a tobacco virus

Pure RNA caused the disease but not protein = RNA is genetic material

Describe the discovery of Transformation principle

Griffith

Dead viral bacteria and alive aviral bacteria in same tube

The bacteria became infectious

Describe the discovery of DNA

Avery, MacLeod, and McCarty’s

Applied different enzymes to destroy parts of cells

found that DNAse destroyed DNA, leading to no death of the mouse

= Proved DNA is the carrier of genetic information

4 components of DNA

1) Phosphate group

2) Deoxyribose Sugar

3) Nitrogenous Base

4) Nucleoside (Deoxyribose+Base)

Describe each nitrogenous base and their size

Adenine - Purine

Guanine - Purine

Cytosine - Pyrimidine

Thymine - Pyrimadine

Uracil - Pyrimadine

Describe main difference between DNA and RNA structure

DNA - Thymine, deoxyribose (1 OH group), dsDNA

RNA - Uracil, ribose (2 OH groups), ssRNA

Chargaff Principle

[A+G]% = [T+C]%

Describe the discovery of DNA structure

Rosalind Franklin

Helix from x-ray of DNA crystals

Waston and Crick used her picture to figure it out lol!

Brief summation of DNA structure

double helix

P groups on outside, nitrogenous bases inside

AT = 2x bond

GC = 3x bond

anti parallel, 5’→3’

DNA pH and charge?

Acidic, negative

What is DNA hybridization

complimentary ssDNA will hybridize to form dsDNA

ssDNA + primers = DNA synthesis

Chromsome structure and difference

Chromosomes are tightly packed DNA

circular: 2kb-5Mb

linear: 50kb-500Mb