4 Extensions - Extending Mendel's Basic idea This lecture...

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Extending Mendel’s Basic idea • This lecture shows a number of examples illustrating the power of Mendel’s basic idea to a number of more complex systems • The general concepts are important, NOT the particular details for each system Basic Concepts • Some alleles can be lethal • Multiple alleles – ABO blood groups • Interaction between alleles at the same locus (dominance) • Interaction between alleles at different loci ( epistasis ) – Modifiers and supressors • Penetrance vs expressivity The mystery of yellow mice • One of the early tests of Mendel’s (rediscovered) results with Lucein Cuenot’s work on the yellow allele in mice – Yellow X non-yellow -> 50% yellow, 50% non- yellow – Yellow X Yellow -> 2/3 yellow, 1/3 non-yellow – No pure-breeding yellow strains found! • How can we account for these ratios? • William Castle (1910) offered the solution: – Yx -> yellow, YY -> lethal!
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• The mouse yellow allele is an example of pleiotropy: an allele influencing two (or more) traits – Here coat color, viability • The Manx gene is cats is another example of an allele lethal as a homozygote – Mm = tailess, MM = dead The environment can influence the phenotype of an allele • The Himalayan allele in rabbits is an example of a temperature-sensitive (ts) allele • The Himalayan allele makes a pigment
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This note was uploaded on 12/09/2009 for the course ECOL 320 taught by Professor Weinert during the Spring '07 term at University of Arizona- Tucson.

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4 Extensions - Extending Mendel's Basic idea This lecture...

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