Mendelian Genetics: Understanding Traits, Genotypes & Phenotypes

These flashcards cover key concepts related to Mendelian genetics, including definitions of traits, inheritance patterns, and key laws.

Genetics

The study of how genes and traits are passed down from one generation to the next.

Trait

A physical characteristic that is inherited from one generation to the next.

Alleles

Alternative versions of a specific gene that account for variation in inherited characteristics.

Dominant Alleles

Alleles that determine the organism's trait and will always show up in the organism if they are present.

Recessive Alleles

Alleles that have a noticeable effect on the organism only when an individual has two copies of that allele.

Law of Segregation

Two alleles for a heritable character segregate during gamete formation and end up in different gametes.

Genotype

The genetic makeup of an organism.

Phenotype

The observable trait or physical manifestation of a genotype.

Punnett Square

A diagrammatic device used for predicting the allele composition of offspring.

Incomplete Dominance

A genetic situation in which neither allele is dominant, resulting in an intermediate phenotype.

Codominance

A genetic situation in which both alleles are expressed separately, resulting in different traits in the individual.

Multiple Alleles

When genes have more than two alleles.

Sex-linked Traits

Inherited traits determined by genes located on sex chromosomes.

X-linked Dominant Traits

Traits where one X chromosome is enough to cause conditions in both females and males.

X-linked Recessive Traits

Traits that require a mutation in both X chromosomes for females, while males only need one X chromosome.

Pedigree

A graphic representation of how a trait is passed from parents to offspring.

Autosomal Dominant

Traits that appear in every generation and affect males and females equally.

Autosomal Recessive

Traits that can skip generations and affect both males and females.

X-linked Dominant Patterns

Affected fathers pass the trait to all daughters but not to sons. More females affected than males.

X-linked Recessive Patterns

More males affected, as affected fathers do not pass the trait to sons.

Homozygous

An organism that has two identical alleles for a specific gene (e.g., AA or aa).

Heterozygous

An organism that has two different alleles for a specific gene (e.g., Aa).

Law of Independent Assortment

A principle stating that each pair of alleles segregates independently of each other pair during gamete formation.

Testcross

Breeding an individual of unknown genotype with a homozygous recessive individual to determine the unknown genotype.

Carrier

A heterozygous individual who carries a recessive allele for a trait or disorder but does not express it phenotypically.

P Generation

The parental, true-breeding generation in a series of genetic crosses.

F1 Generation

The first filial generation; the hybrid offspring produced by crossing the P generation.

F2 Generation

The second filial generation; the offspring resulting from interbreeding or self-pollinating the F1 generation.

Polygenic Inheritance

A pattern of inheritance where multiple genes determine a single physical characteristic, such as height or skin color.

Epistasis

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