Mendelian Genetics and Inheritance Concepts

Vocabulary flashcards covering Mendel, genetics terminology, and inheritance patterns.

True-breeding (homozygous)

Organism that, for a given trait, produces offspring identical to itself when crossed; homozygous for that trait.

Hybrid

Offspring from a cross between true-breeding parents with different traits; also called a cross.

Monohybrid cross

Cross between individuals that differ in only one trait.

P generation

Parental generation of true-breeding individuals used to start a genetic cross.

F1 generation

First filial generation; offspring of the P generation.

F2 generation

Second filial generation; offspring of the F1 cross.

Punnett square

Diagrammatic tool to predict genotype and phenotype frequencies in a cross.

Genotype

Genetic makeup of an individual; the specific alleles present (e.g., AA, Aa, aa).

Phenotype

Physical appearance or trait expressed by an organism.

Dominant allele

Allele that is expressed in the phenotype when present, represented by uppercase letters.

Recessive allele

Allele that is expressed only when the individual is homozygous for it, represented by lowercase letters.

Homozygous

Two identical alleles for a gene (e.g., AA or aa).

Heterozygous

Two different alleles for a gene (e.g., Aa).

Genotype ratio

Proportions of the different genotypes in offspring, such as 1:2:1 in a monohybrid F2 cross.

Phenotype ratio

Proportions of the different phenotypes in offspring, such as 3:1 in a monohybrid F2 cross.

Five-element model

Mendel’s framework: 1) genes pass to offspring; 2) two alleles per trait; 3) alleles differ; 4) alleles segregate; 5) alleles may be latent.

Law of Segregation

Parental alleles separate into gametes and reunite at fertilization; explains 3:1 and 1:2:1 patterns.

Law of Independent Assortment

Alleles of different genes assort independently into gametes; underlies dihybrid 9:3:3:1 phenotypic ratio.

Dihybrid cross

Cross involving two different traits (e.g., seed shape and color).

Independent assortment

Genes for different traits assort into gametes independently, leading to multiple phenotypic combinations.

Linked genes

Genes located close together on the same chromosome that tend to be inherited together and do not assort independently.

Epistasis

One gene affects or masks the expression of another gene, altering expected phenotypes.

Polygenic inheritance

Trait controlled by many genes; produces continuous variation (e.g., height).

Pleiotropy

One gene influences multiple, seemingly unrelated traits (e.g., sickle cell affects multiple systems).

Incomplete dominance

Heterozygote shows an intermediate phenotype (e.g., pink snapdragons from red x white).

Codominance

Heterozygote expresses both parental phenotypes distinctly (e.g., blood type AB).

Multiple alleles

More than two allele options exist for a gene (e.g., ABO blood groups A, B, O).

Latent allele

An allele that is present but not expressed in the phenotype of the heterozygote; may reappear in a later generation.

Environmental effects on phenotype

Environment can influence trait expression (e.g., temperature-sensitive pigment in Siamese cats).