Meiosis, Genetic Variation, and Inheritance Notes

Inheritance (heredity)

The transmission of genes and associated traits from one generation to the next.

Genetics

The study of heredity and inherited variation.

Gametes

Reproductive cells (sperm and eggs) that pass genes to the next generation.

Locus

A gene’s specific position along a chromosome.

Homologous chromosomes

Paired chromosomes (one from each parent) that carry the same genes at the same loci but can carry different alleles.

Meiosis

A process that reduces chromosome number by half, producing haploid gametes (n) from diploid (2n) parent cells.

Diploid (2n)

A cell containing two sets of chromosomes.

Haploid (n)

A cell containing a single set of chromosomes.

Fertilization

The union of a sperm (n) and an egg (n) to form a zygote (2n), restoring diploidy.

Zygote

The diploid cell formed by the union of gametes (fertilization), with 2n = 46 in humans.

Meiosis I

The first meiotic division where homologous chromosomes separate.

Meiosis II

The second meiotic division where sister chromatids separate.

Prophase I

Stage of Meiosis I where homologous chromosomes pair up and crossing over occurs.

Chiasmata

X-shaped regions on homologous chromosomes where crossing over occurred.

Metaphase I

Stage of Meiosis I where pairs of homologous chromosomes line up at the metaphase plate.

Anaphase I

Stage of Meiosis I where homologous chromosomes separate and move toward opposite poles.

Telophase I

Stage of Meiosis I where each half of the cell has a haploid set of duplicated chromosomes; followed by cytokinesis.

Centromere

The DNA region where sister chromatids are held together and where the kinetochore forms.

Kinetochore

A protein complex at the centromere that attaches chromosomes to spindle microtubules.

Crossing over

The exchange of genetic material between non-sister chromatids during prophase I, producing recombinant chromosomes.

Recombinant chromosomes

Chromosomes that carry DNA from both parental origins, formed by crossing over.

Independent assortment

The random orientation of homologous chromosome pairs at the metaphase plate during Meiosis I, leading to varied combinations in gametes.

Random fertilization

The phenomenon that any sperm can fuse with any ovum, dramatically increasing genetic variation.

Allele

Different versions of a gene.

Sister chromatids

Identical copies formed by DNA replication, held together at the centromere.