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In genetics, the coefficient of coincidence (c.o.c.) is a measure of interference in the formation of chromosomal crossovers during meiosis. It is generally the case that, if there is a crossover at one spot on a chromosome, this decreases the likelihood of a crossover in a nearby spot. [1] This is called interference.
Crossover interference is the term used to refer to the non-random placement of crossovers with respect to each other during meiosis.The term is attributed to Hermann Joseph Muller, who observed that one crossover "interferes with the coincident occurrence of another crossing over in the same pair of chromosomes, and I have accordingly termed this phenomenon ‘interference’."
Where d is the distance in map units, the Morgan Mapping Function states that the recombination frequency r can be expressed as =.This assumes that one crossover occurs, at most, in an interval between two loci, and that the probability of the occurrence of this crossover is proportional to the map length of the interval.
There are two distinctive mapping approaches used in the field of genome mapping: genetic maps (also known as linkage maps) [7] and physical maps. [3] While both maps are a collection of genetic markers and gene loci, [8] genetic maps' distances are based on the genetic linkage information, while physical maps use actual physical distances usually measured in number of base pairs.
Genetic linkage is the tendency of DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction.Two genetic markers that are physically near to each other are unlikely to be separated onto different chromatids during chromosomal crossover, and are therefore said to be more linked than markers that are far apart.
The effective population size (N e) is the size of an idealised population that would experience the same rate of genetic drift as the real population. The effective population size is normally smaller than the census population size N, partly because chance events prevent some individuals from breeding, and partly due to background selection and genetic hitchhiking.
The problem is that the term “gene” has been used since the foundation of genetics without a clear understanding of what a gene actually is. So, despite its widespread popular usage, its use is now avoided in genetics journals (see [3] for a discussion about the changing definition of the gene). This is unfortunate for discussions of ...
In population genetics, the Hill–Robertson effect, or Hill–Robertson interference, is a phenomenon first identified by Bill Hill and Alan Robertson in 1966. [1] It provides an explanation as to why there may be an evolutionary advantage to genetic recombination .