BMS2042 Lecture Notes - Lecture 3: Pleiotropy, Wild Type, Thalassemia
Document Summary
Not always simple, transmission of many traits don"t produce mendelian ratios: Extensions to mendel, the laws still apply but different ratios. For non mendelian inheritance, mendel"s laws are not followed. Mendel saw complete dominance in heterozygote only one allele is expressed. Due to 50% gene product being enough for normal phenotype. Sometimes one allele not completely dominant over the other: Incomplete dominance: heterozygote has phenotype intermediate between two homozygotes. Co-dominance heterozygote exhibits both the phenotypes of the two homozygotes. For both of these you see 1:2:1 f2 phenotypic ratio (i. e. not mendelian 3:1) (from klug) In this example, the genotype crcw is not enough for a red phenotype or white phenotype and so this is an incomplete dominance pattern where the f1 generation is intermediate of the two colours producing pink. If you then cross the two pink heterozygous genotypes, you will get a genotypic and phenotypic ratio in f2 of 1:2:1.