BIOL 2107 Lecture Notes - Lecture 4: Heredity, Cystic Fibrosis, Consanguinity
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The punnett square is a simple way to visualize the segregation and random union of. Each f1 hybrid produces two kinds of gametes in a 1:1 ratio. F2 progeny: 3:1 ratio of phenotypes, 1/4 will breed true for the dominant trait, 1/2 will be hybrids, 1/4 will breed true for the recessive trait. F1 will result in f2 of 3:1/1:2:1. 3:1 is the phenotype ratio, 1:2:1 is the genotype ratio. Law of segregation: the gametes are going to be separated, having only one allele. Law of independent assortment: those gametes are going to independently match. Mendel"s dihybrid crosses revealed the law of independent assortment. Mendel tested whether two genes in dihybrids would segregate independently. First, he crossed true-breeding yellow round peas with true-breeding green wrinkled peas to obtain dihybrid f1 plants: yy rr x yy rr f1 yy rr. Then, the dihybrid f1 plants were selfed to obtain f2 plants: f1 yy rr x f1 yy rr f2.