Chapter 5 Flashcards: Genetics

linked genes

Genes located close together on the same chromosome.

linkage group

A group of linked genes.

nonrecombinant (parental) gamete

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

nonrecombinant (parental) progeny

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

recombinant gamete

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) map

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

physical map

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

map unit (m.u.)

Unit of measure for distances on a genetic map; also called a centiMorgan (cM). One map unit equals a 1% recombination frequency.

centiMorgan (cM)

Unit of measure for distances on a genetic map; also called a map unit (m.u.). One map unit equals a 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 expected double crossovers. 

mapping function

Mathematical function that relates recombination frequencies to actual physical distances between genes. 

genetic marker

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 study

Looks for nonrandom 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

Nonrandom association between alleles in a haplotype.

single-nucleotide polymorphism (SNP)

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