Mapping the centromere.
If no crossover event occurs between a gene and the centromere,
the pattern of ascospores within an ascus
due to first-division segregation,
since the two alleles are separated during the first meiotic division. Crossover would produce
due to second-division segregation.
To calculate the distance between the gene and the centromere: d =
((1/2 recombinant asci) / total asci) * 100.
The distance (d in mu) counts half the number of recombinant asci.
since crossing over in each occurs in only two of the four chromatids during meiosis.