Each crossover produces two spores like the parents and two spores that are a result of the crossover. Thus, to determine the number of crossovers, you must divide the number of asci counted by two since only half the spores in each ascus result from crossing over.Click to see full answer. Also know, what does the frequency of crossing over allow scientists to do?Crossing over occurs in the first division of meiosis . Because the frequency of crossing over between any two linked genes is proportional to the chromosomal distance between them, crossing over frequencies are used to construct genetic, or linkage, maps of genes on chromosomes.Also Know, why are there 8 spores in an ascus? Some fungi produce their sexual spores in long, sausage-shaped sacs called asci. There are usually eight spores to an ascus. This is achieved by the ascus generating four sex cells by the normal process of meiosis, and then each of those four cells splitting. Also know, what is the map distance between the gene for spore color and the centromere? You divide the percentage of asci showing crossover by 2 because that is how you calculate the map units and because one map unit equals one recombinant per 100 total events. 2. The published map distance between the spore color gene and the centromere is 26 map units.What is the term for crossing over?Chromosomal crossover, or crossing over, is the exchange of genetic material between two homologous chromosomes non-sister chromatids that results in recombinant chromosomes during sexual reproduction.