Unit 5 - Mendelian Genetics

hybrid

Offspring of crosses between parents with different traits

purebred

the offspring of many generations that have the same traits

homozygous

An organism that has two identical alleles for a trait

heterozygous

An organism that has two different alleles for a trait

genotype

An organism's genetic makeup, or allele combinations.

phenotype

An organism's physical appearance, or visible traits.

genetics

The scientific study of heredity

trait

A characteristic that an organism can pass on to its offspring through its genes.

gene

A segment of DNA on a chromosome that codes for a specific trait

allele

one of a number of different forms of a gene

Principle of dominance

states that some alleles are dominant and others are recessive

recessive

An allele that is masked when a dominant allele is present

dominant

Describes a trait that covers over, or dominates, another form of that trait.

gamete

sex cell

Codominance

A condition in which neither of two alleles of a gene is dominant or recessive.

incomplete dominance

Situation in which one allele is not completely dominant over another allele

multiple alleles

three or more forms of a gene that code for a single trait

polygenic

trait controlled by two or more genes

sex-linked traits

Traits controlled by genes located on sex chromosomes.

pedigree

A diagram that shows the occurrence of a genetic trait in several generations of a family.

karyotype

A display of the chromosome pairs of a cell arranged by size and shape.

carrier

A person whose genotype includes a gene that is not expressed in the phenotype.