History and Experiments

Question 1

What is molecular Biology?

Answer 1

1. hybrid discipline that combines the elements of genetics and biochemistry
2. study of gene structure and function at the molecular level

Question 2

1865-Gregor Mendel

Answer 2

Transmission genetics. Concluded inheritance was particulate that is each parent contributed particles(genes) to the offspring.

Question 3

1910-Thomas Hunt Morgan

Answer 3

Demonstrated eye color in fruit flies was sex-linked. Each gene has locus(place) on chromosomes.

Question 4

Chromosome Theory of Inheritance

Answer 4

idea that chromosomes carry genes

Question 5

The farther apart two genes are on a chromosome…

Answer 5

the more likely they are to recombine.

Question 6

Genetic Mapping

Answer 6

A.H. Sturtevant predicted this mathematical relationship exists between the distance separating two genes on a chromosome and frequency of recombination between the two genes.

Question 7

If two loci recombine with a frequency of 1%

Answer 7

they are separated by a map distance of one centimorgan.

Question 8

Molecular genetics

Answer 8

what genes are made of and how they function.

Question 9

Nuclein

Answer 9

Miescher found the cell contained a mixture of compounds called nuclein.
Major component is DNA.
Second major component is Protein.

Question 10

Nucleotide

Answer 10

sugar + phosphate group + nitrogenous base

Question 11

Three choices likely candidates for genetic material:

Answer 11

1. DNA
2. RNA
3. Protein

Question 12

Avery-MacLeod-McCarty 1944

Answer 12

demonstrated DNA was the genetic material of inheritance.

Question 13

Griffith Experiment-1928

Answer 13

Griffith grew virulent bacteria Streptococcus amoniniae. Live S strain-smooth-capsule-kill mouse. Live R strain-rough-no capsule-do not kill mouse. Heat killed S strain + Live R strain = Mouse Dead.

Demonstrated that TRANSFORMATION occurred cells passed acquired virulence to dependents as heritable trait-laid foundation for DNA as genetic material but what was the chemical nature of the gene.

Question 14

Avery MacLeod McCarty Experiment 1944

Answer 14

1. removed protein from test extract and it still retained transforming ability
2. Digested test extract with various enzymes then tested transforming ability:
   A) Trypsin-protease-No effect on transforming ability
   B) Chymotrypsin-protease-No effect on transforming ability
   C) RNase-nuclease cleaves RNA- No effect
   D) DNase- nuclease cleaves DNA- LOST abiity to transform R strain cells

Question 15

Physical Chemical Analysis of the Purified “Transforming Substance”

Answer 15

1. Ultracentrifugation (MW estimate higher than normal matched with other DNA samples)
2. Electrophoresis (high motility due to high charge to mass ratio of DNA)
3. UV Absorption Spectrometry (matched DNA at 260nm protein is at 280nm)
4. Chemical Analysis (nitrogen to phosphorous ratio 1.67. ratio is higher in proteins)

Question 16

Edward Chargaff 1950

Answer 16

Bases are NOT found in equal proportions.

Question 17

Rollin Hotchkiss

Answer 17

Extended Avery et al. work and purified transforming material so that it only contained 0.02% protein.

Question 18

Hershey-Chase Experiment 1952

Answer 18

T2 bacteriophage made of DNA and protein.
Phage DNA radiolabeled phosphorous-32 and phage protein radiolabeled with sulfur-35.

Radiolabeled protein not transferred in experiment.

Question 19

1953 Watson and Crick

Answer 19

double helical model of DNA and almost all geneticists accepted genes made out of DNA.