Genetics and Inheritance

Gregor Mendel was an Austrian Monk in the late 1800s who experimented with pea plants to find trait inheritance patterns in successive generations.

Mendel's Laws

1. Principle of Segregation - Two alleles of a homologous pair of chromosomes separate (segregate) during gamete formation such that each gamete receives only one allele
2. Principle of Independent Assortment - Alleles of a gene pair assort independently of other gene pairs. The segregation of one pair of alleles in no way alters the segregation of another pair of alleles*

*This law does not always hold, explained later

Terminology

Homozygous - An individual who has two copies of the same allele at a locus

Heterozyous - An individual who has two different alleles at the same locus

Dominant alleles only needs one copy to show the phenotype

Recessive alleles need two copies of the allele to show the phenotype

Co-dominance means the phenotype for the heterozygote is different from either homozygote (Ex. AB blood type)