Chapter 8, Lesson 2

How is Probability Related to Inheritance?

Probability - number that describes how likely it is that an event will occur

The laws of probability predict what is likely to occur, not what will occur

Probability and Genetics

Mendel discovered that probability applies to genetics too

• the probability of a hybrid cross producing the dominant trait is 3 out of 4

Mendel was the first scientist to recognize that genetics could be predicted using probability

Phenotypes and Genotypes

Phenotype - an organisms physical appearance or visible traits

Genotype - an organisms genetic makeup or alleles

Naming Genotypes

Geneticists use other terms to describe genotypes

Homozygous - organism that has two identical alleles for a trait (PP, pp, TT, tt) --> PUREBRED

Heterozygous - organism that has two different alleles for a trait (Pp, Tt) --> HYBRID

Punnett Squares

Punnett Square - chart that shows all the possible ways alleles can combine in a genetic cross

In a genetic cross, the combination of alleles that parents can pass to an offspring is based on probability
Punnett squares can be used to explain why Mendel saw the results he did