Lecture 2 Epistasis

Lecture 2 Epistasis - Genetics can be used to characterize...

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Genetics can be used to characterize biological pathways Epistasis tells which gene products are involved in common pathways and which act earlier or later in a process. Complementation tells us if variation is due to mutations in one gene or several genes.
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Example, flower color
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How many genes affect flower color? How variable are the proteins encoded by those genes? What is the pathway to make flower color?
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What are the relationships between color types? Purple is dominant to White A X Purple RR White A rr Purple Rr Relationship between 2 chosen color variants
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F2 1 RR , 2 Rr and 1 rr X Allelic difference at one locus leads to a characteristic ratio of phenotypes in F2 generation Purple RR White A rr F1 X Purple Rr
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X F1 R/r ; P/p Segregation if the F1 differ at two loci F1 R/r ; P/p 9 purple 7 white Parents: Purple X White A F2
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Punnet Square: Predict the genotypes and phenotypes in the F2 generation when the trait is controlled by two genes with randomly segregating alleles Male gametes Female gametes RP Rp rP rp rp rP RP RRPP RRPp RRPp RrPP RrPp RRpp RrPp Rrpp RrPP RrPp rrPP rrpp RrPp Rrpp rrPp rrPp 9 R_P_ 3 R_pp 3 rrP_ 1 rrpp Phenotypes: if both R and P needed for purple color F2 after RrPp X RrPp Rp 9 purple and 7 white
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diverse recessive mutants, We can identify all the genes specifically involved in making the purple pigment Not all genes in a pathway can be identified as mutants. What is it about a protein that could make it hard to
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Lecture 2 Epistasis - Genetics can be used to characterize...

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