1. 3. Probability and mendelian inheritance (2015)

2. 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

3. 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:

4. 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:

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

6. Codominance and multiple allels
Probability and mendelian inheritance
Codominance and multiple allels