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  Test for Linkage Progreny Counts AA BB aa bb aa bb(P) H 0 : The loci are NOT linked.   calc >   crit H 0 can be rejected. The loci do not.

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Presentation on theme: "  Test for Linkage Progreny Counts AA BB aa bb aa bb(P) H 0 : The loci are NOT linked.   calc >   crit H 0 can be rejected. The loci do not."— Presentation transcript:

1   Test for Linkage Progreny Counts AA BB aa bb aa bb(P) H 0 : The loci are NOT linked.   calc >   crit H 0 can be rejected. The loci do not assort independently. Aa BbAa BbAa BbAa Bb aa bb aa bb Aa Bb Aa bb aa Bb aa bb Obs: 140 Exp:255(250/500) = Obs: 115 Exp:255(250/500) = Obs: 110 Exp:245(250/500) = Obs: 135 Exp:245(250/500) = LOCUS1Aa B b LOCUS 2 Total Total   calc = df = (df rows ) x (df columns ) = 1   crit = 3.841

2 Molecular Basis for Relationship between Genotype and Phenotype DNA RNA protein genotype function organismphenotype DNA sequence amino acid sequence transcription translation

3 One Gene/One Enzyme Hypothesis (Beadle and Tatum) Wild-type Neurospora crassa (red bread mold) is prototrophic. Prototrophs are able to grow on minimal medium. Minimal medium contains only inorganic salts, simple carbon source, and water. Auxotrophs require nutritional supplement(s) for growth.

4 One Gene/One Enzyme Hypothesis (Beadle and Tatum) Conidia are mutagenized with X-ray. Possible mutants are crossed to wild-type and individual ascospores are cultured on complete (permissive) medium. Cultures are plated on minimal medium and auxotrophs are isolated. Auxotrophs are tested for nutritional requirement.

5 One Gene/One Enzyme Hypothesis (Beadle and Tatum) Each requirement for a specific nutrient (mutant effect) followed Mendelian pattern of inheritance. Beadle and Tatum deduced that each mutant was deficient for an essential enzyme in a biosynthetic pathway. compound X compound Y compound Z enzyme Aenzyme B compound X compound Y enzyme A A_B_ A_bb

6 Not All Gene Products are Enzymes! One Gene/One Enzyme One Gene/One Polypeptide (structural proteins, subunits) One Gene/One Product (rRNA, tRNA)

7 Mutants of Arginine Biosynthetic Pathway Mutant 1 Mutant 2 Mutant 3 Mutant 4 citGSAargornglu cit citrulline GSAglutamic semi-aldehyde argarginine ornornithine gluglutamic acid

8 Mutants of Arginine Biosynthetic Pathway cit citrulline GSAglutamic semi-aldehyde argarginine ornornithine gluglutamic acid Order of Compounds in Pathway Determination of Mutant Effects

9 Molecular Basis for Relationship between Genotype and Phenotype DNA RNA protein genotype function organismphenotype DNA sequence amino acid sequence transcription translation

10 null if splice junction is affected no effect if mutation is in the middle of the intron or not the branch point Gene Sites Sensitive to Mutation


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