4. Mendel Inhertence

Mendelian Inheritance

The pattern of inheritance of single-gene traits described by Gregor Mendel through his pea plant experiments.

Gregor Mendel

The scientist whose pea plant experiments established the basic principles of Mendelian inheritance.

Mendel's Pea Plant Experiments

Experiments in which Mendel studied seven distinct traits in pea plants to determine predictable patterns of inheritance.

Seven Traits Studied by Mendel

Seven distinct pea plant traits, including flower color, seed shape, and plant height.

Gene

A discrete unit of heredity that determines or influences a specific trait.

Allele

A different version or form of a gene found at the same locus on homologous chromosomes.

Locus

The specific position of a gene or allele on a chromosome.

Homologous Chromosomes

A pair of chromosomes containing the same genes at corresponding loci, with one chromosome inherited from each parent.

Homozygous

Having two identical alleles at a particular gene locus.

Heterozygous

Having two different alleles at a particular gene locus.

Dominant Allele

An allele whose associated phenotype is expressed in a heterozygous individual under complete dominance.

Recessive Allele

An allele whose associated phenotype is generally masked by a dominant allele in a heterozygous individual and expressed when homozygous.

Mendel's Law of Dominance

The principle that, under complete dominance, the dominant allele masks the effect of the recessive allele in a heterozygous individual.

Mendel's Law of Segregation

The principle that the two alleles of a gene separate during gamete formation, so each gamete receives only one allele.

Segregation

The separation of the two alleles of a gene during gamete formation.

Mendel's Law of Independent Assortment

The principle that alleles of different genes assort independently during gamete formation when the genes are not genetically linked.

Independent Assortment

The independent distribution of alleles of different genes into gametes during meiosis.

Gamete

A haploid reproductive cell that carries one allele for each gene.

Punnett Square

A diagram used to predict the possible genotypes and phenotypes of offspring from a genetic cross.

Genotypic Ratio

The relative proportions of different genotypes expected among offspring from a genetic cross.

Phenotypic Ratio

The relative proportions of different observable traits expected among offspring from a genetic cross.

Genetic Cross

A mating between individuals with known or assumed genotypes used to predict offspring inheritance.

Single-Gene Trait

A trait primarily determined by alleles of a single gene and capable of following Mendelian inheritance patterns.

Mendelian Inheritance in Humans

The inheritance of certain single-gene human traits and disorders according to Mendelian patterns.

Examples of Mendelian Traits and Disorders

Cystic fibrosis, sickle cell anemia, and widow's peak hairline are commonly used examples in introductory Mendelian genetics.

Genotype

The genetic makeup or combination of alleles of an individual.

Phenotype

The observable characteristics of an individual resulting from genotype and environmental influences.

Homozygous Dominant

An individual with two dominant alleles, such as AA.

Heterozygous

An individual with two different alleles, such as Aa.

Homozygous Recessive

An individual with two recessive alleles, such as aa.

AA

A homozygous dominant genotype.

Aa

A heterozygous genotype.

aa

A homozygous recessive genotype.

Mendelian Inheritance Sequence

Parents → gametes → fertilization → offspring genotypes → offspring phenotypes.

Law of Segregation vs Independent Assortment

Segregation separates the two alleles of one gene; independent assortment describes how alleles of different genes are distributed independently during gamete formation.