Chapter 5: Linkage, recombination, and eukaryotic gene mapping

The independent separation of alleles results in…

Recombination

Recombination

The sorting of alleles into new combinations

Linked genes

Genes located close together on the same chromosome.

Linkage group

a group of linked genes.

Non-recombinant (parental) gamates

Gamete that contains only the original combinations of alleles that were present in parents.

Non-recombinant (Parental) progeny

Progeny that possess only the original combinations of alleles that were present in the P generation

Recombinant Gametes

Gamete with new combinations of alleles.

Recombinant Progeny

Progeny with new combinations of alleles formed from recombinant gametes.

Recombination Frequency

Proportion of recombinant progeny produced in a cross

Coupling (Cis) configuration

Arrangement of linked genes in which wild-type alleles of two or more genes are found on one chromosome, and mutant alleles are on the homologous chromosome.

Repulsion (Trans) Configuration

Arrangement of two linked genes in which each of a homologous pair of chromosomes contains one wild-type (dominant) allele and one mutant (recessive) allele

Genetic (Linkage) Maps

Map of the relative distances between genetic loci, markers, or other chromosome regions determined by rates of recombination; measured in recombination frequencies or map unit

Physical Maps

Map of the physical distances between loci, genetic markers, or other chromosome segments, measured in base pairs.

Map Units (m.u.) aka centiMorgans (cM)

Unit of measure for distances of a genetic map one map unit equals 1% recombination frequency:

Two-Point testcross

Cross between an individual heterozygous at two loci and an individual homozygous for recessive alleles at those loci.

Three-point testcross

Cross between an individual heterozygous at three loci and an individual homozygous for recessive alleles at those loci

Interference

Degree to which one crossover interferes with additional crossovers in the same region.

Coefficient of Coincidence

Ratio of observed double crossovers to ecxpected double crossovers

Mapping Functions

mathematical function that relates recombination frequencies to actual physical distances between genes

Genetic Markers

Any variable gene or DNA sequence used to identify a location on a genetic or physical map.

Linkage Analysis

Gene mapping based on the detection of physical linkage between genes, as measured by the rate of recombination in the progeny of a cross

Genome-wide association studies

Looks for non-random associations between the presence of a trait and alleles at many different loci scattered across a genome— that is, for associations between traits and particular suites of alleles in a population.

Haplotype

A specific set of linked genetic variants or alleles on a single chromosome or on part of a chromosome.

Linkage disequilibrium

Non-random association between alleles in a haplotype.

single-nucleotide polymorphisms (SNPs)

A site in the genome where individual members of a species differ in a single base pair.