<P> Because recombination can occur with small probability at any location along chromosome, the frequency of recombination between two locations depends on the distance separating them . Therefore, for genes sufficiently distant on the same chromosome, the amount of crossover is high enough to destroy the correlation between alleles . </P> <P> Tracking the movement of genes resulting from crossovers has proven quite useful to geneticists . Because two genes that are close together are less likely to become separated than genes that are farther apart, geneticists can deduce roughly how far apart two genes are on a chromosome if they know the frequency of the crossovers . Geneticists can also use this method to infer the presence of certain genes . Genes that typically stay together during recombination are said to be linked . One gene in a linked pair can sometimes be used as a marker to deduce the presence of another gene . This is typically used in order to detect the presence of a disease - causing gene . </P> <P> The recombination frequency between two loci observed is the crossing - over value . It is the frequency of crossing over between two linked gene loci (markers), and depends on the mutual distance of the genetic loci observed . For any fixed set of genetic and environmental conditions, recombination in a particular region of a linkage structure (chromosome) tends to be constant, and the same is then true for the crossing - over value which is used in the production of genetic maps . </P> <P> In gene conversion, a section of genetic material is copied from one chromosome to another, without the donating chromosome being changed . Gene conversion occurs at high frequency at the actual site of the recombination event during meiosis . It is a process by which a DNA sequence is copied from one DNA helix (which remains unchanged) to another DNA helix, whose sequence is altered . Gene conversion has often been studied in fungal crosses where the 4 products of individual meioses can be conveniently observed . Gene conversion events can be distinguished as deviations in an individual meiosis from the normal 2: 2 segregation pattern (e.g. a 3: 1 pattern). </P>

What process of genetic recombination involves genes from both parents