Genetics

Genetics

The science behind how traits are passed down from generation to generation.

Heredity

Passing on characteristics from one generation to another.

Trait

A specific characteristic of any living thing.

Gene

A sectioned off piece of chromosome that controls a specific trait.

Allele (Dominant vs. Recessive)

Variation of a gene. Dominant alleles mask up recessive alleles.

Genome

The complete set of genes in an organism

Chromosome

Found in the nucleus of a cell; come in pairs; made of DNA, sectioned off into genes.

Gregor Mendel

“The father of genetics” who determined inheritance patterns by cross-breeding pea plants.

Genotype

The genetic term for a trait (Ex. Homozygous recessive).

Phenotype

The physical trait (Ex. Eye color).

Homozygous Dominant

A characteristic that received dominant traits from both parents. (Ex. AA, HH, DD)

Homozygous Recessive

A characteristic that received recessive traits from both parents. (Ex. aa, hh, dd)

Heterozygous

A characteristic that received a dominant trait from one parent and a recessive trait from the other. (Ex. Aa, Hh, Dd)

Punnett Square

A Punnett square shows the potential outcome of genotypes and phenotypes from one generation to the next.

Monohybrid Cross

Cross between individuals that involves one pair of contrasting traits. (Ex. AA, aa)

Dihybrid Cross

Cross between individuals that have different alleles for the same gene.

Law of Segregation

Alleles separate when gametes form (meiosis); Each parent randomly passes on only allele for each gene.

Law of Independent Assortment

Alleles for different genes separate independently of one another when gametes are formed.

Incomplete Dominance

One allele is not completely dominant over another allele; The phenotype of the heterozygous will be an intermediate between the phenotypes of the homozygous. (Ex, Wavy hair)

Codominance

Both alleles are expressed in heterozygotes. (Ex. Roan Coat)

Multiple Alleles

Gene that has 3 or more alleles; Multiple alleles increase the number of possible phenotypes but ONLY TWO can be inherited. (Ex. Blood)

X-linked Recessive Trait

Affected sons are born to unaffected mothers; skips generations; never passed from father to son; all daughters of affected fathers are carriers.

Polygenic Trait

Trait controlled by two or more genes.

Pedigree

A pedigree shows whether a trait is present or absent in a family.