Intro to Heredity and Mendelian Genetics

Vocabulary practice flashcards covering Mendelian laws of inheritance, key genetic terminology, monohybrid crosses, Punnett squares, and test crosses.

Law of Segregation

A Mendelian principle stating that the two alleles for each gene separate during meiosis, moving from diploid ($2n$) cells into different haploid ($n$) gametes.

Law of Independent Assortment

A Mendelian principle stating that the inheritance or assortment of alleles from one gene pair has no effect on the inheritance or assortment of a different gene pair during meiosis.

Law of Dominance

A Mendelian principle stating that when two different alleles are present in a gene pair, one allele can mask the expression of the other allele so that only the dominant phenotype is expressed.

Dominant Allele

An allele that masks the expression of a recessive allele, requiring only one copy to express the dominant phenotype, and represented by a capital letter (e.g., $R$).

Recessive Allele

An allele that is expressed only in the absence of a dominant allele, requiring two copies to express the recessive phenotype, and represented by a corresponding lowercase letter (e.g., $r$).

P Generation

The parent generation in a genetic cross, representing the original cross of individuals.

F1 Generation

The first filial generation, consisting of the direct offspring produced from a cross of the $P$ generation.

F2 Generation

The second filial generation, consisting of offspring produced from a cross between two $F_1$ generation individuals ($F_1 \times F_1$).

Alleles

Two or more alternative forms of a gene located at the same position (locus) on homologous chromosomes.

Monohybrid Cross

A genetic cross involving a single gene pair.

Genotypic Ratios

The probability or relative proportion of different genotypes occurring in the offspring of a cross.

Phenotypic Ratios

The probability or relative proportion of different physical phenotypes occurring in the offspring of a cross.

Punnett Square

A chart used to determine possible combinations of alleles in offspring and predict genotypes and phenotypes by writing possible gametes of one parent along the top and the other parent along the left side.

Test Cross

A genetic cross between an individual displaying an unknown dominant phenotype and an individual displaying a recessive phenotype to determine whether the unknown genotype is homozygous or heterozygous.

Test Cross Results for Homozygous Dominant

If the unknown dominant parent in a test cross is homozygous, all offspring will display the dominant phenotype, and none will display the recessive phenotype.

Test Cross Results for Heterozygous

If the unknown dominant parent in a test cross is heterozygous, half of the offspring will display the dominant phenotype and half will display the recessive phenotype.