Recombination - Part 1

Flashcards on Recombination - Part 1 from Genetics and Molecular Biology lecture

Law of Independent Assortment (Law of Reassortment)

The alleles of different genes segregate independently of one another during gametogenesis and are distributed independently of one another in the next generation.

Linked genes

Genes located on the same chromosome that tend to be inherited together.

Cis (coupling) configuration

Mutant alleles of both genes are on the same chromosome (e.g., ab/AB).

Trans (repulsion) configuration

Mutant alleles are on different homologues of the same chromosome (e.g., Ab/aB).

Allele

Alternative forms of a given gene.

Crossing over (or recombination)

The exchange of DNA from one homologous chromosome to another, leading to new allele combinations.

Recombinant

An individual or gamete with a new combination of alleles not found in the parental generation.

Test crosses

Genetic crosses used to determine the genotype of an individual by mating it with a homozygous recessive individual.

Linkage group

All known genes on a chromosome.

Linked Genes Recombination Frequency

Genes with recombination frequencies less than 50 percent are on the same chromosome.

Unlinked Genes

Genes that undergo independent assortment, having a recombination frequency of 50 percent, located on nonhomologous chromosomes or far apart on the same chromosome.

Genetic maps

Gene mapping methods use recombination frequencies between alleles to determine the relative distances between them.

Distance measurement

1 map unit = 1 percent recombination (true for short distances) = 1 centimorgan.

Most frequent types of gametes in a genetic cross

Nonrecombinant gametes; these provide the linkage phase (cis versus trans) of the alleles in the multiply heterozygous parent.

The two rarest classes in a genetic cross identify the

Double-recombinant gametes.

Linkage groups

Genes connected by linkage relationships.