Tuesday 04/15/25 Genetics I

Phenotype

The physical manifestation or observable traits of a gene or set of genes.

Genotype

The genetic makeup of an organism, specifically the alleles it possesses.

Alleles

Different versions of the same gene found at the same locus on homologous chromosomes.

Homozygous

An organism that has two identical alleles for a particular gene.

Heterozygous

An organism that has two different alleles for a particular gene.

Dominant allele

An allele that expresses its trait even when only one copy is present in the genotype.

Recessive allele

An allele that expresses its trait only when two copies are present in the genotype.

Principle of Segregation

The principle stating that alleles for each gene segregate into gametes during meiosis, so each gamete carries only one allele for each gene.

Principle of Independent Assortment

The principle that states that genes on different chromosomes assort independently of one another during gamete formation.

Meiosis

A type of cell division that reduces the chromosomal number by half, resulting in gametes.

Punnett Square

A diagram used to predict the outcome of genetic crosses by showing all possible gamete combinations.

F1 generation

The first generation of offspring resulting from a cross between two parental organisms.

F2 generation

The second generation of offspring, produced by crossing the F1 generation.

True breeding

Organisms that produce offspring identical to themselves when self-fertilized.

Pea plants

The organisms used by Gregor Mendel to study inheritance and genetic traits.

3:1 ratio

The typical phenotypic ratio observed in the offspring of a monohybrid cross of heterozygous parents.

Gametes

Reproductive cells (sperm and egg) that carry only one allele for each gene.

Crossing Over

The exchange of genetic material between homologous chromosomes during meiosis, leading to genetic variation.

Diploid

Cells that contain two complete sets of chromosomes, one from each parent.

Random Orientation

The process during metaphase I of meiosis where chromosomes align independently of each other.

Homozygous dominant

An organism with two dominant alleles for a particular gene (e.g., AA).

Homozygous recessive

An organism with two recessive alleles for a particular gene (e.g., aa).

Dihybrid Cross

A genetic cross examining two traits at once, using individuals that vary in two characteristics.

Foil method

A mathematical technique used to determine the possible combinations of alleles in gametes during dihybrid crosses.

Seed color gene

A gene that has alleles A (yellow) and a (green) affecting the color of seeds.

Seed texture gene

A gene that has alleles B (smooth) and b (wrinkled) affecting the texture of seeds.

Inheritance

The process by which genetic information is passed from parents to offspring.

Mathematical Rules of Probability

Rules used to predict the likelihood of inheriting particular traits based on genetic crosses.

Genetic Makeup

The specific combination of alleles an organism carries for a particular trait.

Physical Appearance

The visual characteristics of an organism, influenced by its genotype.

Reappearing recessive traits

The phenomenon where recessive traits can appear in the offspring when two heterozygous organisms breed.

Gamete formation

The process by which gametes are produced during meiosis, separating alleles for each gene.

Monohybrid Cross

A genetic cross examining only one trait between two organisms.

Organism’s trait

A characteristic of an organism that is determined by its genotype.

Self-fertilization

The process in which an organism fertilizes its own gametes, leading to offspring.

Green seeds (trait)

The phenotype resulting from inheriting two recessive alleles (aa) for seed color.

Yellow seeds (trait)

The phenotype resulting from inheriting at least one dominant allele (A) for seed color.

Traits of pea plants

Seven easily observable characteristics studied by Mendel, such as seed color and texture.