6F Genetics

Gregor Mendel

Genetics

• the study of heredity and the variation of inherited characteristics.

Gene

• a unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring.

Trait

• Physical characteristics or attributes of an organism that are expressed by genes such as eye color, hair color, leaf shape, etc…

Allele

• one of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.

Homozygous

• refers to having two of the same alleles for a single trait.

• Ex: AA or aa

• Both alleles are either dominant or recessive

Heterozygous

• refers to having two different alleles for a single trait.

• Ex: Aa

• One allele is dominant while the other allele is recessive

Dominant Allele

• an allele that produces the same phenotype whether its paired allele is identical or different

• Ex: A (with a capital letter)

Recessive Allele

• an allele that produces its characteristic phenotype only when its paired allele is identical.

• Ex: a (with a lower case letter)

Genotype

• the genetic makeup of an organism or group of organisms with reference to a single trait, set of traits, or an entire complex of traits.

• Ex: AA, Aa or aa

Phenotype

• the set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.

• Ex: brown eye color, blond hair color

Monohybrid Cross

• a genetic cross using a single trait with two alleles.

• Ex: AA x aa

Dihybrid Cross

• In a genetic cross, a hybridization using 2 traits with 2 alleles each

• Ex: AABB x aabb

Dihybrid Cross