Heredity: Inheritance and Variation

This flashcard set covers the foundational concepts of heredity, including Mendel's laws, genetic terminology, and non-Mendelian inheritance patterns such as incomplete dominance and codominance.

Gregor Mendel

The Founder of Modern Genetics who conducted studies with the edible pea plant ($Pisum\,sativum$) due to its numerous distinct varieties.

Pisum sativum

The scientific name for the edible pea plant used by Gregor Mendel in his genetic studies.

Traits

Features passed from the parent species to new individuals by the carrier of discrete units.

Genes

Discrete units where each unit expresses itself independently in the offspring.

Alleles

The two alternative pairs of a gene, in which one pair from each parent is transferred to the offspring.

Homozygous genotype

An individual condition where a gene carries two identical forms of alleles.

Heterozygous genotype

An individual condition where a gene carries two different types of alleles (dominant and recessive).

Genotype

The specific arrangement of alleles for a given pair of genes, often represented by uppercase (e.g., $D$) and lowercase (e.g., $d$) letters.

Phenotype

The visible traits of an organism, such as colour, length, and shape, that result after gene expression.

Punnett Square

A tool used to predict the possible genotypes and phenotypes of offspring from a cross or breeding event.

Law of Dominance

Mendelian law stating that in two dissimilar alleles, the dominant factor will always mask the recessive form.

Law of Segregation

Mendelian law stating that the two copies of each gene separate during meiosis cell division, resulting in each gamete carrying only one member of an allele.

Law of Independent Assortment

Mendelian law stating that the assortment of a single paired gene is independent of the other pair at the time of gametogenesis.

Non-Mendelian Patterns of Inheritance

Any pattern of inheritance wherein traits do not segregate according to Mendel's laws.

Incomplete Dominance

A form of intermediate inheritance where one allele for a specific trait is not completely dominant over the other, resulting in a third phenotype that combines the dominant and recessive traits.

Codominance

A pattern of inheritance where both alleles are expressed equally in the phenotype of the heterozygote, such as in roan cows or human blood types.

Antigen

A protein-bound to a sugar molecule found on the surface of red blood cells that helps determine blood type.

AB Blood Type

The human blood phenotype resulting from the expression of codominant $I^A$ and $I^B$ alleles.

Type O Blood

The human blood phenotype that requires two recessive $O$ alleles ($ii$) to be present.