Untitled Flashcard Set

Griffith

Goal: To test if proteins or DNA contained genetic material

Test:

Two strains of pneumonia

  1. Strain R (nonpathogenic)

  2. Strain S (pathogenic)

  • Injected into mice

  • Heated up Strain S, would’ve denatured proteins

    • Mouse still lived

  • Mixed heated up strands with straint, somehow mouse died

  • Meant that strain R absorbed DNA from strain S, as proteins would’ve been denatured

Conclusion: DNA contains genetic material


H.J. H Muller

Just wanted to make mutants, used radiation to make mutations in horseflies


Oswald Avery

  • Took over Griffith experiment

    • Showed that DNA was transformation factor


Chargaff (1950)

Goal: To support Avery’s findings

How: Professor didn’t go into it

Two rules we must know

  1. Amount of A, T, C, G (in DNA) varies between species

  2. In each species, %A=%T and %C=%G


Hershey-Chase (1952)

Goal: To determine whether or not the protein was genetic material or if DNA had it

How: Using bacteriophages tagged with radioactive labels

  • P for nucleic acids, s for protein coat

  • If virus injects DNA into bacteria, bacteria would be radioactive

    • This would confirm that DNA contains genetic material


Watson & Crick as well as Franklin & Walkins (1953)

  • Franklin & Walkins were x-ray crystallographers

    • Trying to find DNA shape

  • Watson & Crick used Franklin’s data to model DNA

    • Discovered that DNA is a double helix shape


Lederberg & Tarium

Goal: Determine if bacteria sexually mate & recombine

How: Two bacteria that we reverse strains

Strain A: met- bio+ thr+ leu- thi+

Strain B: met+ bio- thr- leu+ thi-

  • Mixed together, put on mm that had nothing. Bacteria colonies formed.

  • Means new colonies had DNA from both strain A & B


Bernard Davis (U-Tube experiment)

Goal: Prove that it was actual sexual reproduction, not bacteria picking up dead bacteria genes

How: Strain A & Strain B placed in U tube with finer filter between them

  • If not reproduction, then bacteria should be able to survive on m.m. with nothing

Conclusion: No colonies formed, its sexual reproduction


William Hayes

Goal: Determine that genes are transferred in one direction

How: Strain A was given streptomyosin slowly kills them, mixed with colonies

  • Reversed it, but no colonies formed

Discovered that bacteria has fertility factors

  • Due to pili

    • F- cannot reproduce

    • F+ can reproduce

    • HFr= reproduce alot


Jacob & Monod

Discovered promoter sequence in DNA that starts RNA tanscription


Meselson & Stahl (1958)

Goal: To demonstrate how DNA is replicated

How: Made DNA out of heavy 15N

  • After replicating x multiple generations, discovered that DNA centrifuged into 2 layers

  • Proved semiconservative model 


Gene Linkage (Morgan’s Lab)

  • Discovered that genes close together are more likely to intent together


  • Recombination frequency= # of recombinants/total # of possible recombinants

  • Use z test to either accept H+ (independent assortment) or reject H+ (gene linkage)

  • Mapped in map units/M.V.

How to find M.V. when order is not known

  1. Organized by parentals and recombinants

  2. Pick one parental & one double reconjoinant

  • If differ by one gene, that gene is the middle

  1. DRAW IT OUT

  2. Matk?


Kornberg (1958)

Goal: Discover enzyme that synthesizes DNA

How: Using bacteria, discovered how DNA was synthesized

Conclusion: DNA polymerase replicates DNA strand with help from helicase


Altaman & Cech

Theorized that RNA initially stored genetic info before DNA