BJU Life Science Chapter 4

Gregor Mendel

Father of genetics

traits

Characteristics that are inherited

purebred

An organism that always produces offspring with the same traits as the parent.

hybrid

An organism that has two different alleles for a trait

dominant trait

a genetic factor that blocks another genetic factor

recessive trait

a genetic factor that is blocked by the presence of a dominant factor

simple dominance

the cross of two genes in which one is dominant over recessive

heredity

Passing of traits from parents to offspring

allele

Different forms of a gene

Punnett Square

A chart that shows all the possible combinations of alleles that can result from a genetic cross

genotype

genetic makeup of an organism. The letters that symbolize an organism's alleles for a specific gene. Ex. Bb, BB, bb

Phenotype

An organism's physical appearance, or visible traits. Determined by the genotype.

incomplete dominance

A pattern of inheritance in which two alleles, inherited from the parents, are neither dominant nor recessive. The resulting offspring have a phenotype that is a blending of the parental traits.

Codominance

A condition in which neither of two alleles of a gene is dominant or recessive. Both alleles are seen in the offspring.

genetic drift

random change in allele frequencies that occurs in small populations

character

A characteristic of a species such as size or shape.

Adaptation

An inherited trait that helps an organism survive and reproduce

trait

A form of a character such as tall or short.

polygenic inheritance

a pattern of inheritance that occurs when two or more genes interact to control a single character

genetic drift

A natural process in which the ratio of alleles in the population changes randomly over time.

natural selection

the process through which organisms with certain adaptations survive to pass on their traits to a greater number of offspring than other organisms do.