Mendelian Genetics - Simple Traits and Punnett Square

Vocabulary flashcards covering key Mendelian concepts, genotype/phenotype, Punnett squares, and simple traits discussed in the lecture notes.

Allele

A variant form of a gene; e.g., R (dominant) and r (recessive) for tongue rolling.

Dominant allele

An allele that expresses its trait even when only one copy is present; represented by uppercase letters (e.g., R).

Recessive allele

An allele that is expressed only when two copies are present (homozygous recessive, e.g., rr).

Heterozygous

A genotype with two different alleles (Rr); phenotype shows the dominant trait (tongue rolling).

Homozygous

A genotype with two identical alleles (RR or rr); RR shows the dominant trait, rr shows the recessive trait.

Genotype

The genetic makeup of an individual—the specific alleles present (e.g., RR, Rr, rr).

Phenotype

The observable trait of an organism (e.g., ability to roll the tongue).

Punnett square

A diagram used to predict the probabilities of offspring genotypes from parental genotypes.

Mendelian trait

A trait that follows a simple dominant–recessive inheritance pattern.

Tongue rolling

A simple Mendelian trait example where rolling is caused by the dominant allele.

Attached ear lobes

A simple Mendelian trait phenotype where the ear lobes are attached to the head.

Unattached ear lobes

A simple Mendelian trait phenotype where the ear lobes hang free.

Cleft chin

A chin with a crease or dimple; cited as a simple Mendelian trait.

Hand clasping

A trait used as an example of a simple Mendelian trait (pattern not specified in notes).

Polygenic trait

A trait controlled by multiple genes, such as eye color, often with environmental influence.

Environmental influence

Environmental factors can affect trait expression even for genetically influenced traits.

Genetic oversimplification

Statements like a single “alcoholism gene” are oversimplifications; real traits are often complex.