Evolutionary Biology: Mendel and Basic Genetics

Flashcards covering key vocabulary from the lecture on Mendel and basic genetics, including Mendelian laws, crosses, and extensions to Mendelian inheritance.

Blending inheritance

The incorrect theory that parental traits mix and permanently merge in offspring.

True breeding plants

Plants that produce offspring with the same trait as themselves when self-pollinated.

Hybrids

Offspring resulting from the cross of two genetically different parents, often true-breeding parents.

P generation

The true-breeding parental generation in a genetic cross.

Cross fertilize

To deliberately mate two different individuals or organisms.

F1 generation

The first filial generation; the direct offspring of the P generation.

Self cross

The process of self-pollinating an individual from the F1 generation.

F2 generation

The second filial generation; the offspring produced by self-crossing or intercrossing the F1 generation.

Monohybrid cross

A genetic cross between parents that differ in only one specific heritable character.

Mendel's five element model

A set of five principles proposed by Mendel to explain the inheritance of traits: factors are transmitted, two copies per trait, different factors yield different traits, factors don't blend, and factors can be latent.

Factors (Mendelian)

Mendel's term for discrete units of heredity, now known as genes.

Latent traits

Traits coded for in an organism's genetic material but not expressed in its phenotype.

Homozygote

An individual having two identical alleles for a specific gene.

Heterozygote

An individual having two different alleles for a specific gene.

Phenotype

The observable physical traits or characteristics of an organism, resulting from its genotype and environmental interactions.

Genotype

The genetic constitution of an individual organism, specifically the set of alleles for a particular gene.

Dominant allele

An allele whose trait is expressed in the phenotype even when only one copy is present (in a heterozygote).

Recessive allele

An allele whose trait is only expressed in the phenotype when two copies are present (in a homozygote).

Principle of Segregation (Mendel’s 1st Law)

States that two alleles for a heritable character segregate (separate) from each other during gamete formation and are rejoined at random during fertilization.

Punnett Square

A diagram used to predict the probable outcomes of a genetic cross, showing all possible combinations of alleles from contributing parents.

Dihybrid cross

A genetic cross involving two different traits, with each parent contributing alleles for both traits.

Principle of Independent Assortment (Mendel’s 2nd Law)

States that alleles for different traits assort independently of one another during gamete formation.

Gene linkage

The phenomenon where genes located close together on the same chromosome tend to be inherited together, defying independent assortment.

Polygenic inheritance

A type of inheritance where a single phenotypic trait is determined by the additive effect of two or more genes.

Epistasis

A gene interaction where the phenotypic expression of one gene (epistatic gene) masks or modifies the effect of another gene (hypostatic gene).

Pleiotropy

The effect of a single gene on multiple, seemingly unrelated phenotypic traits.

Incomplete dominance

A form of inheritance in which the heterozygous phenotype is an intermediate blend of the two homozygous phenotypes.

Codominance

A form of inheritance in which both alleles in a heterozygote are fully and separately expressed, resulting in a phenotype that shows characteristics of both parental traits unblended.

Environmental effects on gene expression

The influence of external or non-genetic factors on how genes are expressed, leading to variations in phenotype.

Alleles

Different forms or variants of a gene.

Gametes

Haploid reproductive cells (sperm and egg) that carry one allele for each gene.

Monohybrid ratios

The expected ratios of genotypes and phenotypes in the F2 generation of a monohybrid cross (e.g., 1:2:1 genotype, 3:1 phenotype).

Dihybrid ratios

The expected phenotypic ratio in the F2 generation of a dihybrid cross, assuming independent assortment (e.g., 9:3:3:1).

Gregor Mendel

An Austrian monk and botanist whose research on pea plants established the fundamental laws of heredity, often called the 'father of genetics'.

Traits

Distinguishing qualities or characteristics of an organism that are often heritable.