A particularly important category of genetic linkage has to do with the X and Y sex chromosomes. These not only carry the genes that determine male and female. How to determine recombination frequency for a pair of genes. Crossovers during meiosis happen at more or less random positions along the chromosome, so the frequency of To do so, we can start by crossing two homozygous flies as shown below: .. How can you create a tester to test if the trait is sex - linked?. Across species, different sexes are often characterized by different types and numbers of sex Because sex chromosomes contain different numbers of genes , different species of organisms have developed . XX females and XY males must find alternative ways to equalize X- linked gene expression among differing sexes. Sex linkage applies to genes that are located on the sex chromosomes. X & Y and Z & W are just two of the ways that sex is determined in animals. Study sex chromosomes, sex - linked inheritance, x-linked traits, y-linked part whose genes do not have corresponding alleles in the other sex chromosome. Since males and females do not have the same sex chromosomes, there will This is because colorblindness is a sex - linked, recessive trait.