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Most recombination occurs naturally and can be classified into two types: (1) interchromosomal recombination, occurring through independent assortment of alleles whose loci are on different but homologous chromosomes (random orientation of pairs of homologous chromosomes in meiosis I); & (2) intrachromosomal recombination, occurring through ...
This principle of "independent assortment" of genes is fundamental to genetic inheritance. [28] However, the frequency of recombination is actually not the same for all gene combinations. This leads to the notion of "genetic distance", which is a measure of recombination frequency averaged over a (suitably large) sample of pedigrees.
In this example, the recombination frequency is 50% since 2 of the 4 gametes were recombinant gametes. [citation needed] The recombination frequency will be 50% when two genes are located on different chromosomes or when they are widely separated on the same chromosome. This is a consequence of independent assortment. [citation needed]
Although an autosomal chromosome contains genes that are passed down from parents to children via independent assortment from only one of the two parents, genetic recombination (chromosomal crossover) mixes genes from non-sister chromatids from both parents during meiosis, thus changing the genetic composition of the chromosome.
The rate of recombination of two discrete loci corresponds to their physical proximity. Alleles that are closer together have lower rates of recombination than those that are located far apart. The distance between two alleles on a chromosome can be determined by calculating the percentage or recombination between two loci.
Causes of differences between individuals include independent assortment, the exchange of genes (crossing over and recombination) during reproduction (through meiosis) and various mutational events. There are at least three reasons why genetic variation exists between populations.
Recombination theory allows for the calculation of x(t), the expected frequency of E2 in association with the allele ΔF508 in generation t, and y, the frequency of E2 on chromosomes without the ΔF508 allele. The recombination rate, c, is assumed to be known, and so the allele age can be calculated as an estimate of t. [4] [5]
In the absence of evolutionary forces other than random mating, Mendelian segregation, random chromosomal assortment, and chromosomal crossover (i.e. in the absence of natural selection, inbreeding, and genetic drift), the linkage disequilibrium measure converges to zero along the time axis at a rate depending on the magnitude of the ...