Mendel's Principles and Complex Inheritance Patterns

Genotype

The genetic makeup of an organism

Sickle cell disease

An example of pleiotropy and co-dominance

Alternative versions of genes

Alleles account for variations in inherited characters

Parental genotype

The genetic makeup of the parents

Expected pattern

The predicted outcome of a genetic cross

Dominant allele

An allele that determines the organism's appearance

Homologous pair

A pair of chromosomes that may be homozygous or heterozygous for a gene

Multiple alleles

Different versions of a gene

Complex inheritance patterns

Patterns of inheritance that are not as simple as Mendel's pea plants

Incomplete dominance

When a heterozygote displays an intermediate phenotype

Polygenic inheritance

When multiple genes contribute to a single phenotype

Environmental impact

The effect of the environment on phenotype

Heat-sensitive alleles

Alleles that are only expressed in certain temperature conditions

Arctic foxes

Animals that produce fur pigment only in warm temperatures

Law of segregation

Two alleles for heritable character separate during gamete formation

Law of independent assortment

Each pair of alleles separates independently during gamete formation

Phenotype

The physical appearance of an organism

Test crosses

Used to infer genotype when phenotype is the same

F1 hybrids

Offspring resulting from a cross between two different parental genotypes

Recessive allele

An allele that has no noticeable effect on appearance

Frequency of alleles

The occurrence rate of different alleles in a population

Polydactyly

The condition of having extra fingers or toes

Hereditary factors

Genes that determine inherited traits

Chromosomes

Structures composed of DNA and histones that carry genes

Diploid organisms

Organisms with two copies of each chromosome

Gene

A discrete unit of inheritance that codes for a specific polypeptide chain or RNA molecule

Gene interaction

The way genes interact with each other and the environment to produce a phenotype

Chromosome theory of inheritance

The theory that genes are located on chromosomes and undergo segregation and independent assortment

Co-dominance

When alleles with separate effects are both expressed

Pleiotropy

When a single gene affects multiple phenotypic traits

Mendelian genetics with multiple genes

When traits are determined by more than one gene

Epistasis

When one gene alters the phenotypic expression of another gene

Trait's norm of reaction

The range of phenotypes produced by a given genotype under different environmental conditions