3. Probability and mendelian inheritance (2015)

Probability and mendelian inheritance The rules of probability apply to the main events that determine the genotypes of offspring. These events are the formation of gametes during meiosis and the union of gametes during fertilization. To determine the expected percents of different genotypes in the offspring of two parents, genetists use a simple tool called Punnett square. Fertilization pollen Gamete formation egg Punnett square

In pea plants, purple flower (P) is dominant to white (p). Probability and mendelian inheritance Problem samples - Problem 1 In pea plants, purple flower (P) is dominant to white (p). If a homozygous plant with white flowers is fertilized with the pollen from a heterozygous plant with purple flowers, what are the possible phenotypes and genotypes of their offspring? Key to phenotypes Parent’s phenotype ♂ Parent’s phenotype ♀ Parent’s genotype ♂ Parent’s genotype ♀ Possible gametes ♂ (pollen) Possible gametes ♀ (egg cell) F1 Phenotype ratio: Genotype ratio:

Probability and mendelian inheritance Problem samples - Problem 2A In a certain breed of rabbits, black fur (B) is dominant to white (b). a. If a homozygous black male is crossed with a heterozygous female, what are the possible phenotypes and genotypes of their offspring? Parent’s phenotype ♂ Parent’s phenotype ♀ Parent’s genotype ♂ Parent’s genotype ♀ Possible gametes ♂ Possible gametes ♀ F1 Phenotype ratio: Genotype ratio:

Probability and mendelian inheritance Inheritance is often more complex than the that studied by Mendel in pea plants. Incomplete dominance

Codominance and multiple allels Probability and mendelian inheritance Codominance and multiple allels