Genetics Week 4

Centimorgans (cM)

a unit of measure of recombination frequency. One cM is equal to a 1% chance that a marker at one genetic locus will be separated from a marker at a second locus due to crossing-over in a single generation.

Genetic Markers

genes identifiable through phenotypic variants that can serve as points of reference in determining whether particular progeny are the result of recombination.

Linkage group

a group of genes chained together by linkage relationships (genes are on the same chromosome)

Physical Distance

measures the number of nucleotides between the two genes or positions on a chromosome.

Recombination Spots

small DNA regions where the frequency of recombination is much higher than average.

Coefficient of Coincidence

the ratio between the actual frequency of double crossovers observed in an experiment and the number of double crossovers expected on the basis of independent probabilities.

Genetic Interference

Occurrence of crossover in one portion of a chromosome interferes with crossover in an adjacent part of the chromosome

Map unit (m.u.)

a unit of measure of recombination frequency. One m.u. is equal to a 1% chance that a marker at one genetic locus will be separated from a marker at a second locus due to crossing-over in a single generation.

Recombinant type

phenotypes reflecting a new combination of genes that occurs during gamete formation.

Genetic Distance

Genetic distance measures the genetic divergence between species or between populations within a species

Linked/unlinked

describes genes whose alleles are inherited together more often than not; linked genes are usually located close together on the same chromosome

Parental type/classes

phenotypes that reflect a previously existing parental combination of alleles that is retained during gamete formation/ combinations of alleles present in the original parental generation.

Recombination frequency

the percentage of recombinant progeny; can be used as an indication of the physical distance separating any two loci on a chromosome.