Biology 1 Honors Unit 6: Genetics and Meiosis Vocabulary

Allele

Different versions of a gene (e.g., blue eye allele, brown eye allele).

Homozygous

Having two identical alleles for a gene (e.g., BB or bb).

Heterozygous

Having two different alleles for a gene (e.g., Bb).

Dominant

An allele that masks the effect of a recessive allele (e.g., B in Bb).

Recessive

An allele that is masked by a dominant allele; only expressed in homozygous form (e.g., bb).

Genotype

The genetic makeup of an organism (e.g., BB, Bb, or bb).

Phenotype

The physical expression of a trait (e.g., brown eyes or blue eyes).

Traits

Characteristics that are inherited (e.g., eye colour, height).

Genetics

The study of heredity and the variation of inherited traits.

Gene

A segment of DNA that codes for a specific protein or trait.

Punnett Square

A diagram used to predict the outcome of genetic crosses.

Monohybrid Cross

A genetic cross involving one trait (e.g., height).

Dihybrid Cross

A genetic cross involving two traits (e.g., height and eye colour).

Testcross

A cross between an organism with an unknown genotype and a homozygous recessive organism to determine the unknown genotype.

Law of Segregation

During gamete formation, alleles for each gene separate so each gamete receives one allele.

Law of Independent Assortment

Genes for different traits are inherited independently of each other.

Probability

The likelihood of a particular genetic outcome.

P Generation

The parental generation in a genetic cross.

F1 Generation

The first generation of offspring from the parental cross.

F2 Generation

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

Carrier

An individual who has one copy of a recessive allele but does not express the trait.

Sex-Linked Genes

Genes located on the sex chromosomes (X or Y).

Incomplete Dominance

A situation where neither allele is completely dominant, resulting in a blended phenotype (e.g., red + white = pink).

Codominance

A situation where both alleles are fully expressed (e.g., red and white spots).

Polygenic Traits

Traits controlled by multiple genes (e.g., skin colour, height).

Pedigree

A chart used to trace the inheritance of traits through generations.

Karyotype

A visual representation of all the chromosomes in a cell.

Gametes

Sex cells (sperm and egg) that contain half the number of chromosomes.

Fertilized Egg

A zygote formed by the fusion of sperm and egg during fertilisation.

Fertilisation

The process of combining sperm and egg to form a zygote.

Somatic Cells

Body cells that contain a full set of chromosomes (not involved in reproduction).

Homologous Chromosomes

Pairs of chromosomes that have the same genes but may have different alleles.

Autosomes

Chromosomes that are not sex chromosomes.

Sex Chromosomes

Chromosomes that determine an organism's sex (e.g., X and Y).

Sexual Reproduction

A type of reproduction involving the fusion of gametes.

Diploid

A cell containing two sets of chromosomes (one from each parent).

Haploid

A cell containing only one set of chromosomes (e.g., gametes).

Meiosis

A type of cell division that reduces the chromosome number by half, producing gametes.

Meiosis I

The first division in meiosis where homologous chromosomes separate.

Meiosis II

The second division in meiosis where sister chromatids separate.

Crossing Over

The exchange of genetic material between homologous chromosomes during meiosis.

Independent Assortment

The random distribution of homologous chromosomes during meiosis.

Genome

All of an organism’s genetic material.

Purebred

Organism whose ancestors are genetically uniform.

Cross

Mating of two organisms.