History and Experiments Flashcards
What is molecular Biology?
- hybrid discipline that combines the elements of genetics and biochemistry
- study of gene structure and function at the molecular level
1865-Gregor Mendel
Transmission genetics. Concluded inheritance was particulate that is each parent contributed particles(genes) to the offspring.
1910-Thomas Hunt Morgan
Demonstrated eye color in fruit flies was sex-linked. Each gene has locus(place) on chromosomes.
Chromosome Theory of Inheritance
idea that chromosomes carry genes
The farther apart two genes are on a chromosome…
the more likely they are to recombine.
Genetic Mapping
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.
If two loci recombine with a frequency of 1%
they are separated by a map distance of one centimorgan.
Molecular genetics
what genes are made of and how they function.
Nuclein
Miescher found the cell contained a mixture of compounds called nuclein.
Major component is DNA.
Second major component is Protein.
Nucleotide
sugar + phosphate group + nitrogenous base
Three choices likely candidates for genetic material:
- DNA
- RNA
- Protein
Avery-MacLeod-McCarty 1944
demonstrated DNA was the genetic material of inheritance.
Griffith Experiment-1928
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.
Avery MacLeod McCarty Experiment 1944
- removed protein from test extract and it still retained transforming ability
- 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
Physical Chemical Analysis of the Purified “Transforming Substance”
- Ultracentrifugation (MW estimate higher than normal matched with other DNA samples)
- Electrophoresis (high motility due to high charge to mass ratio of DNA)
- UV Absorption Spectrometry (matched DNA at 260nm protein is at 280nm)
- Chemical Analysis (nitrogen to phosphorous ratio 1.67. ratio is higher in proteins)
Edward Chargaff 1950
Bases are NOT found in equal proportions.
Rollin Hotchkiss
Extended Avery et al. work and purified transforming material so that it only contained 0.02% protein.
Hershey-Chase Experiment 1952
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.
1953 Watson and Crick
double helical model of DNA and almost all geneticists accepted genes made out of DNA.
