Genetics: Mendel's Principles and Inheritance Patterns

Sickle-Cell Anemia

A genetic disorder that develops when a person inherits two mutated copies of a gene that codes for a subunit of hemoglobin.

Gregor Mendel

The scientist who discovered the fundamental rules that govern inheritance.

Blending Theory of Inheritance

The belief held until about 1900 that offspring are a blend of parental traits.

True-Breeding Garden Peas

Pea plants that are pure-breeding, meaning they produce offspring with the same traits when self-fertilized.

Cross-Fertilization

The process of fertilizing flowers using pollen from a different plant, preventing self-fertilization.

Parental Generation (P generation)

The true-breeding plants used in an initial cross.

Filial Generation (F1 generation)

The first generation of offspring from a cross.

F2 Generation

The generation produced by self-pollination of individuals from the F1 generation.

3:1 Ratio

The ratio of purple to white flowers observed in the F2 generation from Mendel's crosses.

Homozygote

A true-breeding individual with both alleles of a gene being the same.

Heterozygote

An individual with two different alleles of a gene.

Monohybrid

An F1 heterozygote produced from a cross that involves a single character.

Monohybrid Cross

A cross between two individuals that are each heterozygous for the same pair of alleles.

Genotype

The genetic constitution of an organism in terms of genes and alleles.

Phenotype

The observable appearance of an organism.

Homozygous Dominant

Genotype PP, which produces the purple phenotype.

Heterozygous

Genotype Pp, which also produces the purple phenotype.

Homozygous Recessive

Genotype pp, which produces the white phenotype.

Mendel's Principle of Segregation

The principle stating that pairs of alleles segregate as gametes are formed.

Gametes

Haploid cells produced during gamete formation that carry one allele from each pair.

Alleles

Different forms of a gene that can exist at a specific locus.

Characters

Heritable features that have alternative forms or traits.

Crosses with One Character

Mendel's experiments involving true-breeding plants with a single trait.

Probability

Mathematical chance of an outcome occurring.

Product Rule

Multiply probabilities of independent events.

Sum Rule

Add probabilities of mutually exclusive outcomes.

Testcross

Cross dominant phenotype with homozygous recessive.

Dihybrid

F1 from a cross of two characters.

Dihybrid Cross

Cross between two heterozygous individuals.

Phenotypic Ratio

Observed ratio of traits in offspring.

Independent Assortment

Genes assort independently during gamete formation.

Locus

Specific location of a gene on a chromosome.

Incomplete Dominance

Heterozygote phenotype is intermediate.

Codominance

Both alleles expressed equally in heterozygotes.

Multiple Alleles

More than two alleles exist for a gene.

Epistasis

One gene masks effects of another gene.

Polygenic Inheritance

Multiple genes influence a single trait.

Pleiotropy

Single gene affects multiple traits.

ABO Blood Group

Blood types determined by three alleles.

Mendel's Principle of Segregation

Alleles segregate during gamete formation.

Mendel's Principle of Independent Assortment

Different traits independently assort in gametes.

Punnett Square

Tool for predicting offspring genotypes.

Gamete Formation

Process of producing reproductive cells.

Chromosome Theory of Inheritance

Genes located on chromosomes, inherited together.

Sutton's Chromosome Theory

Chromosomes behave like alleles during inheritance.

Quantitative Traits

Traits influenced by multiple genes.

Bell-Shaped Curve

Graphical representation of polygenic traits.

Insulin Resistance

Condition influenced by epistatic gene interactions.

Allele

Variant form of a gene.

Dominant Allele

Allele that masks the effect of another.

Recessive Allele

Allele whose effects are masked by dominant.

Genetic Cross

Breeding experiment to analyze inheritance.

F1 Generation

First filial generation from parental cross.