crossing over
The reciprocal exchange of genetic material between nonsister chromatids during synapsis of meiosis I.

(KY-as-muh) (plural, chiasmata) The X-shaped, microscopically visible region representing homologous chromatids that have exchanged genetic material through crossing over during meiosis.

gel electrophoresis
(JELL eh-LEK-troh-for-EE-sis) The separation of nucleic acids or proteins, on the basis of their size and electrical charge, by measuring their rate of movement through an electrical field in a gel.

homologous (homologous chromosomes)
(home-OL-uh-gus) Chromosome pairs of the same length, centromere position, and staining pattern that possess genes for the same traits at corresponding loci. One homologous chromosome is inherited from the organism's father, the other from the mother.

linked genes
Genes that are located on the same chromosome.

(LIH-pid) One of a family of compounds, including fats, phospholipids, and steroids, that are insoluble in water.

(LOH-kus) (plural, loci) A particular place along the length of a certain chromosome where a given gene is located.

The general term for the production of offspring that combine traits of the two parents.

A family tree describing the occurrence of heritable characters in parents and offspring across as many generations as possible.

restriction fragment length polymorphisms (RFLPs)
Differences in DNA sequence on homologous chromosomes that result in different patterns of restriction fragment lengths (DNA segments resulting from treatment with restriction enzymes); useful as genetic markers for making linkage maps.

Southern blotting
A hybridization technique that enables researchers to determine the presence of certain nucleotide sequences in a sample of DNA.

The pairing of replicated homologous chromosomes during prophase I of meiosis.

An aberration in chromosome structure resulting from an error in meiosis or from mutagens; attachment of a chromosomal fragment to a nonhomologous chromosome.