lecture 6

Question 1

Explain the One-gene One-enzyme hypothesis

Answer 1

• almost all metabolic pathways are multisept processes - one step is controlled by a different enzyme, thus different gene
• work done largely by Archibald Garrod
• Beadle and Tatum

Question 2

define: auxotroph, prototroph, minimal media

Answer 2

• auxotroph: organism that cannot grow on mm due to mutation; metabolic mutants
• prototroph: organism that can grow on mm; wildtype
• minimal media: lab growth medium containing essential nutrients

Question 3

Explain Archibald Garrod(?)’s experiment

Answer 3

• induced mutation in wt neurospora
• select for organism that lose ability to grow MM
• many vials undergoing mutagenesis, found vial with no growth then went back to strain on cm; challeneged mutant strain to grow in mm supplemented with different intermediates
• focused on arginine auxotrophs
• knew: enzyme catalyzed rxns are multistep and 2 intermediates in arg syn (ornithine and citrulline)
• later become - one gene-one polypepetide hypothesis

Question 4

Explain complementation

define: allelic and non-allelic

Answer 4

• Beadle and Tatum
• determined that the mutations were in separate genes because supplementation with differnet intermediates was sufficient to allow growth
• if they are mutations in the same gene = they DO NOT compliment = alleilic
• if mutations are on different genes = they COMPLIMENT = not allelic
• cross 2 homo mutant lines
• if het is wt pheno = mutant strains have mutations in different genes that affect different steps of pathway
• if het is mutant pheno = mutant strain have mustation in same gene