Genetics and Mendelian Inheritance

Vocabulary-style flashcards covering the concepts of Mendelian inheritance, genetic crosses, polygenic traits, and specific genetic phenomena like pleiotropy and codominance.

Monohybrid Cross

Single gene inheritance where the principle of segregation explains the behavior of alternative forms of a single gene trait.

Mendelian Monohybrid Ratio

The proportion of phenotypes in the $F_{2}$ generation resulting in $3$ dominant to $1$ recessive ($3:1$).

Dihybrid Cross

A genetic cross that explores the behavior of two different traits in a single cross.

Recombinants

Phenotypes that emerge in the $F_{2}$ generation that differ from the parental phenotypes, such as wrinkled yellow and round green seeds in Mendel's experiments.

Punnett Square

A diagrammatic representation named after the English Geneticist R.C. Punnett used to show the results of crossing generations.

Mendel's Second Law of Heredity (Independent Assortment)

States that in a dihybrid cross, alleles of each gene assort independently of each other into gametes.

Test Cross

A procedure for revealing unknown genotypes by crossing an individual of unknown genotype with an individual of a known homozygous recessive genotype.

Trihybrid Inheritance

The inheritance of three characters at the same time, producing $8$ different phenotypes in the $F_{2}$ generation in a typical ratio of $27:9:9:9:3:3:3:1$.

Polygenic Inheritance

A pattern of inheritance where more than one gene affects a single trait, resulting in many new combinations of genes.

Continuous Variation

A gradation in the degree of difference observed in a group consisting of many individuals, occurring when several genes influence a particular character.

Pleiotropy

The phenomenon whereby a single gene affects more than one trait; an allele with more than one effect on a phenotype is said to be pleiotropic.

Sickle Cell Disease

A classical example of pleiotropy where a single gene controls approximately six phenotypes, including abnormal Hb, sickling, and increased resistance to malaria caused by Plasmodium falciparum.

Multiple Alleles

A genetic situation where more than two alleles exist at a single gene locus.

Codominance

An effect exhibited by multiple alleles where both alleles of a pair are fully expressed in the heterozygote.