BIOA01H3 Lecture Notes - Lecture 32: Neurospora Crassa, Francis Crick, Auxotrophy
13 May 2018
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BIOA01
LEC 32: Central Dogma
Nov 20, 2015
• DNA → RNA → Protein
→ Beadle and Tatum’s Experiments
- worked with neurospora
- auxotroph mutants→ cant grow on a diet, have to have all food given to them
- hypothesized that each gene f this had a defect that made the auxotroph not
be able to grow without the amino acid (they first thought it was one gene-
one enzyme hypothesis)
- *;ater updated to one gne-one polypeptide hypothesis
→ How to grow a mold
- provided all required nutrients→ complete medium
- mm→ minimal medium (provide only most basic nutrients needed for
growth)
they used Neurospora crassa
- could grow on salt and water
- ARG mutants→ can grow on mm only if Arginine was added
- Test these Arg mutants for ability to grow on MM when each of the following
were added : Ornithine, Citrulline, Argininosuccinate, Arginine
*** LOOK AT RESULTS ON SLIDES
Results:
→ Dissecting the pathway to Arginine
→ DNA to RNA to Protein
- proposed that one gene encoded one enzyme
- ** one gene-one polypeptide hypothesis: majority of genes code for cellular
proteins → updated bc one enzyme/ protein can have more than one polypeptide ,
each encoded by different gene
→ Blocking Enzyme Pathways
Alkaptonuria
- mutations in HGO (homogentisic oxidase gene→ deficiency in enzyme homogentisic
oxidase and accumulation in homogentisic acid → results in urine turning black when
coming into contact with air
→ Pathway from Gene to Polypeptide
Francis crick gave the idea of Central Dogma : info flows from DNA to RNA to
Protein
- transcription : info encoded in DNA is made into complementary RNA copy
find more resources at oneclass.com
find more resources at oneclass.com
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Document Summary
Nov 20, 2015: dna rna protein. Auxotroph mutants cant grow on a diet, have to have all food given to them. Hypothesized that each gene f this had a defect that made the auxotroph not be able to grow without the amino acid (they first thought it was one gene- one enzyme hypothesis) Mm minimal medium (provide only most basic nutrients needed for growth) they used neurospora crassa could grow on salt and water. Arg mutants can grow on mm only if arginine was added. Test these arg mutants for ability to grow on mm when each of the following were added : ornithine, citrulline, argininosuccinate, arginine. Proposed that one gene encoded one enzyme. ** one gene-one polypeptide hypothesis: majority of genes code for cellular proteins updated bc one enzyme/ protein can have more than one polypeptide , each encoded by different gene.
