Glossary

Allele
alternative forms of a gene, one inherited from each parent

Centimorgan (cM)
measure of genetic distance between two loci based on the number of recombination events occurring between them, I cM = roughly I x 106 base pairs

Genetic heterogeneity
mutations in different genes produce a clinically similar picture

Informative marker
a marker with many alleles of relatively even frequency distribution with a polymorphism information content of at least 0.5

Linkage
a measure of the degree to which alleles at two loci fail to assort independently during meiosis and are inherited together some fraction of the time.

Linebreeding
breeding between related individuals (known as inbreeding between first?degree relatives

Locus
location of a gene or anonymous DNA sequence on a chromosome. Linkage or genetic map shows order and genetic distances between loci on a chromosome

Lod score
log of the odds supporting linkage of two loci. Traditionally, a lod score of three or greater is accepted as evidence of linkage between two markers or a marker and a disease gene

Marker Assisted Selection
use of genetic markers for selection of a linked characteristic, trait, or disease associated gene

Microsatellite markers
short tandem reiterated nucleotide sequences, usually (CA) 13 (CA)20, also known as short tandem repeat polymorphisms (STRP) or simple sequence tandem repeats (SSTR) that are flanked by unique sequence PCR primers (usually twenty mers in length)

Polymerase I Chain Reaction (PCR)
Utilizes oligonucleotide primers and a heat stable DNA polymerase to amplify a segment of DNA. Permits rapid genotyping of marker alleles from minute amounts of genomic DNA

Recombination
physical and breakage and reunion of chromosomal DNA