Biology Chapter 10: Meiosis and Variation

Vocabulary terms and definitions covering the differences between asexual and sexual reproduction, chromosomal terminology, the mechanisms of genetic variation, and the phases of meiosis.

Asexual Reproduction

A process requiring DNA from only one parent where offspring are genetically identical clones produced via mitosis; mutations are the only source of variation.

Sexual Reproduction

A process where offspring receive half of their DNA from a female parent and half from a male parent, resulting in genetically different offspring; requires meiosis, mitosis, gamete formation, and fertilization.

Heredity

The transmission of traits from one generation to the next.

Genetics

The scientific study of heredity and inherited traits.

Genes

Hereditary units that code for specific traits, consisting of DNA sequences that code for proteins and enzymes.

Alleles

Different forms of the same gene.

Locus

A gene’s specific location on a chromosome.

Chromosomes

Single pieces of DNA containing $100\text{'s to } 1000\text{'s}$ of genes; humans have $46$ in each body cell.

Homologous Chromosomes

Also known as homologs or homologous pairs; a pair of chromosomes with the same length, centromere position, and staining pattern that control the same traits.

Sex chromosomes

Chromosomes that determine the sex of an individual; $XX$ for female and $XY$ for male.

Autosomes

The $22$ pairs of human chromosomes that are not sex chromosomes.

Diploid cell ($2n$)

A cell containing both members of a homologous pair; example includes somatic cells.

Haploid cell ($n$)

A cell containing only one chromosome belonging to a homologous pair; example includes gametes.

Fertilization

The joining of an egg and a sperm cell.

Zygote

A diploid fertilized egg.

Crossing over

The exchange of pieces of chromosomes between non-sister chromatids of homologous pairs during Prophase I, creating new combinations of alleles.

Independent assortment

The random orientation of pairs of homologous chromosomes during Metaphase I, where maternal and paternal chromosomes do not necessarily stay together.

Reduction division

Another name for Meiosis I because the number of chromosomes is cut in half.

Tetrads

A paired structure consisting of two homologous chromosomes (four chromatids total) that forms during Prophase I.

Anaphase I

The phase of meiosis where homologous pairs are split apart and one member moves towards each pole.

Telophase II/Cytokinesis

The final stage of Meiosis II where four varied daughter cells form, each with half the number of chromosomes as the original cell.