Genetics and Mendelian Inheritance: Key Terms and Laws

Gene

sequence of DNA that codes for a protein and thus determines a trait

Phenotype

An organism's physical appearance, or visible traits.

Genotype

Genetic makeup of an organism

Allele

An alternative form of a gene.

Heterozygous

An organism that has two different alleles for a trait

Homozygous

An organism that has two same alleles for a trait

Codominance

A condition in which both alleles for a gene are fully expressed. (Both show up)

Incomplete Dominance

When both alleles are "mixed together" (Red and Blue = Purple)

Epistasis

interaction between alleles in which one allele hides the effects of another allele

Gametes

reproductive cells

Meiosis

Cell division that produces reproductive cells in sexually reproducing organisms

Law of Segregation

When gametes are made, the two alleles must seperate (Bb, only one allele can get the B or the b)

Independent Assortment

One gene does not affect how another gene is passed down.

Mutation

change in a DNA sequence that affects genetic information

Radiation, Chemicals, Excess Heat

Examples that cause mutation.

Nondisjunction

Extra or missing chromosomes (Down's Syndrome)

Defective Gene

Doesn't produce the correct protein

Human Genetic Disorders

Can be dominant, recessive, sex-linked, epistatic, and variable expressed.

Linkage

Genes on the same chromosome inherited together.