Genes in the differential region of the X show an inheritance pattern called X linkage ; those in the differential region of the Y show Y linkage. Eye color in Drosophila was one of the first X-linked traits to be identified, and Thomas Hunt Morgan mapped this trait to the X chromosome in Although the Y chromosome contains a small region of similarity to the X chromosome so that they can pair during meiosis, the Y chromosome is much shorter and contains many fewer genes.
The crosses are illustrated diagrammatically in Figure 4. Operations Management. Now, consider a cross between a homozygous white-eyed female and a male with red eyes Figure 2. Electrical Engineering. Mendel hypothesized that there were heritable factors, later called genescontrolling the development of those characteristics.
These specimens were isolated and back crossed to create stable phenotypic strains.
When a gene being examined is present on the X chromosome, but not on the Y chromosome, it is said to be X-linked. Sex-linked inheritance regularly shows different phenotypic ratios in the two sexes of progeny, as well as different ratios in reciprocal crosses.
At meiosis in females, the two X chromosomes pair and segregate like autosomes so that each egg receives one X chromosome. Red eye color is wild-type and is dominant to white eye color. Eye color in Drosophila was one of the first X-linked traits to be identified, and Thomas Hunt Morgan mapped this trait to the X chromosome in
In these organisms, there are two categories of chromosomes, sex chromosomes and autosomes the chromosomes other than the sex chromosomes. What ratio of offspring would result from a cross between a white-eyed male and a female that is heterozygous for red eye color?
Because of the location of the eye-color gene, reciprocal crosses do not produce the same offspring ratios. Figure 1.