Patterns of Inheritance and Mendel's Principles

Heredity

the passing of traits from one generation to the next.

Trait

inherited feature passed down through generations.

Genetics

the science of heredity and hereditary variation.

Gregor Mendel

Considered the father of genetics.

Homologous chromosome

chromosomes that carry genes for the same traits.

Gene

discrete packets of DNA (region of a chromosome) that code for a trait.

Alleles

alternative versions of a gene.

Dominant allele

always expressed when present (capital letter).

Recessive allele

Only expressed when paired with another recessive allele; masked in the presence of a dominant allele (lower case).

Mendel's Law of Segregation

Describes the Inheritance of a Single Character.

Homozygous

An organism that has two identical alleles for a gene.

Heterozygous

An organism that has two different alleles for a gene.

Genotype

the listing of alleles (letter code) an individual carries for a specific gene.

Phenotype

the physical expression of a trait.

Punnett Square

A Punnett square shows the four possible combinations of alleles that could occur when gametes combine.

Monohybrid cross

parents only differ in one character.

Probability

compares one group of offspring to the whole (%).

Ratio

compares 2 or more groups of offspring to each other (:).

Dominant Disorder

genetic disorders inherited as dominant traits controlled by a single gene.

Recessive Disorder

genetic disorders inherited as recessive traits controlled by a single gene.

Incomplete Dominance

Gene interaction in which both alleles of a gene are partially expressed, often resulting in an intermediate or different phenotype.

Heterozygous Advantage

describes the case in which the heterozygous genotype has a higher relative fitness than either the homozygous dominant or homozygous recessive genotype.

Sickle Cell Disorder

Example of a recessive disorder where the phenotype is affected by the genotype.

Polydactylism

Example of a dominant disorder where the phenotype is affected by the genotype.