Mendelian Genetics Lecture Notes

Vocabulary flashcards summarizing the key terms and definitions from the lecture on Mendel’s experiments and genetic principles.

Blending Inheritance

The discredited hypothesis that parental traits physically mix in offspring, producing intermediate phenotypes (e.g., white × purple flowers → light-purple flowers).

Phenotype

The observable physical or physiological trait of an organism, such as seed shape or flower color.

True-Breeding (Pure Line)

A population that, when self-pollinated, produces offspring with identical, predictable phenotypes generation after generation.

Self-Pollination

Fertilization of a plant with its own pollen, often achieved by covering flowers to prevent external pollen transfer.

P Generation

The parental, true-breeding generation used to start a Mendelian cross.

Hybrid

An offspring produced by crossing two different true-breeding parents; symbolized as F1 in Mendelian experiments.

F1 Generation

The first filial generation, consisting of hybrids produced from a cross between P-generation parents.

F2 Generation

The second filial generation, obtained by crossing or selfing individuals from the F1 generation.

Dominant Allele

An allele that masks the expression of its alternative (recessive) allele in a heterozygote and determines the phenotype.

Recessive Allele

An allele whose phenotype is expressed only when present in two copies (homozygous) and is masked by a dominant allele in heterozygotes.

Allele

An alternative version of a gene that occupies a specific locus on a chromosome.

Genotype

The combination of alleles present in an organism (e.g., AA, Aa, or aa) that determines genetic potential.

Homozygous Dominant

A genotype with two identical dominant alleles (e.g., AA).

Homozygous Recessive

A genotype with two identical recessive alleles (e.g., aa).

Heterozygous

A genotype possessing one dominant and one recessive allele for a given gene (e.g., Aa).

Monohybrid Cross

A genetic cross tracking the inheritance of a single trait, such as seed shape (round vs. wrinkled).

Dihybrid Cross

A genetic cross tracking two different traits simultaneously, such as flower color and seed color.

Punnett Square

A diagram that predicts genotypic and phenotypic ratios of offspring by combining possible gametes from each parent.

Principle of Dominance

Mendelian principle stating that when two different alleles are present, only the dominant allele is expressed in the phenotype.

Principle of Segregation

Mendelian principle stating that the two alleles for a gene separate randomly into different gametes during meiosis.

Principle of Independent Assortment

Mendelian principle stating that alleles of different genes segregate into gametes independently of one another.

Dependent Assortment Hypothesis

The (unsupported) idea that alleles of different genes remain linked together during gamete formation, limiting allele combinations.

Independent Assortment Hypothesis

The idea (supported by Mendel’s dihybrid cross) that alleles of different genes assort into gametes independently, producing all combinations.

Particulate Inheritance

Mendel's model proposing that discrete units (alleles) determine traits and are transmitted intact across generations.

Pedigree Analysis

A family-history method for tracing inheritance; if two identical-phenotype parents have a child with a new phenotype, the child is homozygous recessive and the parents are heterozygous.