Unit 1: Mendelian Laws of Inheritance

Vocabulary flashcards summarizing key terms and definitions from the Mendelian Laws of Inheritance lecture.

Genetics

The biological discipline that studies heredity and genetic variation.

Heredity (Inheritance)

The transmission of traits from parents to their offspring.

Genetic variation

The degree of DNA difference among individuals within a population.

Gene

A basic unit of heredity; a DNA segment that encodes information for a trait.

Allele

An alternative form of a gene found at a specific locus.

Locus

The fixed position a gene occupies on a chromosome.

Homologous chromosomes

A pair of chromosomes, one from each parent, carrying the same sequence of genes.

Genotype

The allelic makeup of an organism for a given gene or set of genes.

Phenotype

The observable expression of a genotype as physical or biochemical traits.

Dominant allele

An allele that masks the expression of a recessive allele in heterozygotes.

Recessive allele

An allele whose expression is masked by a dominant allele in heterozygotes.

Homozygous

Having identical alleles for a given gene (e.g., TT or tt).

Heterozygous

Having two different alleles for a given gene (e.g., Tt).

True-breeding

Producing offspring with the same trait over many generations; genetically homozygous for the trait.

Hybrid

The offspring resulting from a cross between parents with different traits; typically heterozygous.

Transmission genetics (Mendelian genetics)

The subfield that investigates patterns of inheritance across generations.

Molecular genetics

The study of DNA structure, gene expression, and regulation at the molecular level.

Cytogenetics

The branch of genetics that examines chromosome structure and behavior during meiosis.

Population genetics

The study of how evolutionary forces affect allele frequencies in populations.

Gregor Mendel

Austrian monk (1822–1884) known as the father of modern genetics for his pea-plant experiments.

Pisum sativum

The garden pea species used by Mendel as a model organism.

Model organism

A species chosen for research due to practical advantages such as easy cultivation and short generation time.

Hybridization

The deliberate mating of individuals with different traits to study inheritance.

Self-pollination

Fertilization in which pollen from a plant fertilizes ovules of the same plant.

Cross-fertilization

Transfer of pollen from one plant to fertilize the ovule of another plant.

Monohybrid cross

A genetic cross tracking inheritance of a single contrasting trait.

Dihybrid cross

A genetic cross tracking inheritance of two contrasting traits simultaneously.

Principle of Dominance

Mendel’s concept that in heterozygotes one allele (dominant) masks another (recessive).

Law of Segregation

Mendel’s first law stating that allele pairs separate randomly into gametes during meiosis.

Law of Independent Assortment

Mendel’s second law stating that alleles of different genes segregate into gametes independently.

Punnett Square

A diagrammatic tool for predicting genetic cross outcomes by combining parental gametes.

P generation

The true-breeding parental individuals in a genetic cross.

F1 generation

The first filial generation; offspring of the P generation.

F2 generation

The second filial generation; offspring resulting from crosses among F1 individuals.

Gametogenesis

The formation of haploid gametes (sperm or eggs) via meiosis.

Anaphase I (Meiosis)

The meiotic phase where homologous chromosomes—and therefore allele pairs—separate, underpinning Mendel’s laws.

Pangenesis

An obsolete theory positing that all body parts release “seeds” that combine in offspring.

Homunculus theory

An outdated idea that a miniature human resides in the sperm