Mendel Genetics Notes

Gregor Mendel –Austrian Monk in the late 1850s

            --first person to run genetics experiments; studied pea plants

                        --characteristics are easily observed, and plants can be cross-pollinated by hand

--Mendel could control which plants produced offspring and observe the resulting characteristics

--observed tall/short; white flowers/purple flowers; green pods/yellow pods; round seeds/wrinkled seeds; etc

            --proposed that each plant inherited 2 genes for each trait (one from each parent)

                        (each parent passes on one chromosome from each pair (1/2 of a pair))

            --one possible gene is dominant (always expressed/visible)

                        --represented by a capital letter

            --one possible gene is recessive (can be hidden/masked by dominant gene)

                        --represented by a lowercase letter

Allele—variant of a gene (for example, a gene can be either the dominant or recessive allele)

Genotype—two alleles that represent the characteristics (example: BB)

Phenotype—characteristic that is actually expressed (example: brown hair)

Homozygous—both alleles are the same

            Homozygous dominant—2 dominant alleles (BB)

            Homozygous recessive—2 recessive alleles (bb)

Heterozygous—2 alleles are different (one dominant, one recessive) (Bb)

Codominance—2 types of alleles are both dominant, so end up seeing both (stripes, dots, etc)

Incomplete Dominance—2 types of alleles are both dominant, and they mix (example: red and white mix to show pink)