Biology chapter 17

True-breeding

Organisms that, when self-fertilized, produce offspring identical to themselves for a specific trait.

Self-fertilization

The process where an organism fertilizes itself, leading to offspring with the same genetic makeup.

Cross fertilization (hybridization)

The mating of two different true-breeding individuals to produce offspring with mixed traits.

Trait

A specific characteristic or feature of an organism, such as flower color or seed shape.

Genotype

The genetic makeup of an organism, represented by alleles (e.g., AA, Aa, aa).

Phenotype

The observable characteristics or traits of an organism resulting from the genotype and environment.

Heterozygous

An organism with two different alleles for a trait (e.g., Aa).

Homozygous

An organism with two identical alleles for a trait (e.g., AA or aa).

P generation

True-breeding parents (e.g., AA x aa).

F1 generation

All offspring are heterozygous (e.g., Aa).

F2 generation

Offspring from F1 self-fertilization resulting in a 3:1 phenotype ratio (dominant to recessive) and a 1:2:1 genotype ratio (1 AA: 2 Aa: 1 aa).

Law of Segregation

During gamete formation, the two alleles for a trait segregate from each other so that each gamete carries only one allele.

Testcross

To determine the genotype of an individual with a dominant phenotype by crossing it with a homozygous recessive individual.

Gametes

The sex cells that carry alleles for a trait.

Dihybrid Crosses

Crosses that examine the inheritance of two different traits simultaneously.

Law of Independent Assortment

States that alleles for different traits are distributed to gametes independently of one another.

Pleiotropy

When one gene influences multiple traits.

Dominant trait

A trait that masks the expression of a recessive trait.

Lethal recessive diseases

Diseases that can persist in a population because carriers do not show symptoms.

Norm of reaction

The range of phenotypes that can result from a single genotype due to environmental influences.

ABO blood system

Demonstrates both complete dominance and codominance in blood types.

Incomplete Dominance

Neither allele is completely dominant, resulting in a blend of traits.

Codominance

Both alleles are expressed equally in the phenotype.

Environmental influence on phenotype

Conditions, like temperature, that can affect the expression of traits.