Genetic distance has nothing at all to do with any actual physical measure of distance. Genetic distance is a value used to reflect a degree of genetic divergence. Statistical distances like a genetic distance are not related to physical space at all - they are measures of statistical difference/similarity (that is they are measures of the difference between two probability distributions).
Two populations with identical allele frequencies for a given gene would have a Genetic Distance of zero. The genetic distance would increase as the differences in allele frequency between the two populations increases.
There are multiple algorithms for calculating genetic distance - Nei's distance, Cavalli-Sforza distance, Reynolds, Weir, and Cockerham's distance, and others. These algorithms reflect different assumptions about forces driving each population's allelic probability distribution.
Genetic distance has nothing at all to do with any actual physical measure of distance. Genetic distance is a value used to reflect a degree of genetic divergence. Statistical distances like a genetic distance are not related to physical space at all - they are measures of statistical difference/similarity (that is they are measures of the difference between two probability distributions).
Two populations with identical allele frequencies for a given gene would have a Genetic Distance of zero. The genetic distance would increase as the differences in allele frequency between the two populations increases.
There are multiple algorithms for calculating genetic distance - Nei's distance, Cavalli-Sforza distance, Reynolds, Weir, and Cockerham's distance, and others. These algorithms reflect different assumptions about forces driving each population's allelic probability distribution.
Thanks for the info, Michael Black
so what is difference between intra and inter genetic distances?
Physical distance = the number of nucleotides between two genes or two positions on a chromosome.
You can think of the chromosome as a meter stick and each nt has a number position starting with number 1 and going to the last nucleotide (normally for tomatoes this might be 56,000,000). So to calculate the distance between two nucleotides, you subtract the numbers corresponding to the two positions. This would be the same as asking the number of mm between 200 mm position and 350mm position, it is 150 mm. But in the case of the nucleotides you have 1,400,000 nt position number and 1,550,000 nt position number, so you subtract these two and you get 150,000 nt as the number of nucleotides between the two positions.
On a practical basis for tomatoes, there is about 1,000,000 nt for each 1cM or a recombination frequency of 1%.
Genetic distance in centimorgans:
https://sciencing.com/calculate-centimorgans-8493492.html
https://www.ndsu.edu/pubweb/~mcclean/plsc731/analysis/analysis5.htm
https://video.search.yahoo.com/yhs/search;_ylt=A0geK9iJKMZaGXcA1GwPxQt.;_ylu=X3oDMTByMDgyYjJiBGNvbG8DYmYxBHBvcwMyBHZ0aWQDBHNlYwNzYw--?p=how+do+determine+centimorgan+distances&fr=yhs-adk-adk_sbnt&hspart=adk&hsimp=yhs-adk_sbnt#id=1&vid=6dbd88fbd1c67d8310648ccd08daa6ef&action=view
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