Extensions of Mendelian Analysis Interactions between alleles of one gene. Multiple alleles, incomplete dominance, codominance Interactions between alleles of two genes New phenotypes, epistasis Relationship between genotype phenotype lethals, variable penetrance, conditional alleles
Extensions of Mendelian Analysis • Interactions between alleles of one gene. • Multiple alleles, incomplete dominance, codominance • Interactions between alleles of two genes. • New phenotypes, epistasis • Relationship between genotype & phenotype • lethals, variable penetrance, conditional alleles
Interactions between alleles of one gene Dominance is a relationship between two alleles of the same gene. Several relationships are possible: complete dominance partial dominance incomplete dominance codominance overdominance Each relationship has particular characteristics
Interactions between alleles of one gene • Dominance is a relationship between two alleles of the same gene. • Several relationships are possible: • complete dominance • partial dominance/ incomplete dominance • codominance • overdominance • Each relationship has particular characteristics
Dominance is relative: an allele can be dominant to one allele and recessive to a third allele w/wa= red eye wa is recessive) w/ w1= red eye(w1 is recessive) wa/w1=light orange(wa is partially dominant to w1) The white gene has many different alleles, each producing a different amount of pigment: eosin, apricot, buff, etc
• Dominance is relative: an allele can be dominant to one allele and recessive to a third allele. w+ / wa = red eye (wa is recessive) w+ / w1 = red eye (w1 is recessive) wa / w1 = light orange (wa is partially dominant to w1 ). The white gene has many different alleles, each producing a different amount of pigment: eosin, apricot, buff, etc
agouti agout agouti AA agouti x black backlycllow bolly agouti AA Aa gout black gouti AA black backryellow belly x black black back/yellow belly a Dominance series: A> al>a
L Phenotype of first parent L Phenotype of second parent Type of dominance AIA A2/A2 A' / A2hybrids Complete A is dominant to A2 A2 is recessive to a A is dominant to aT Complete A' is recessive to a' Aand A are incompletely Incomplete dominant relative to each other and A2 are codominant Codominant relative to each other