In the diagram at the right, a cell heterozygous for a gene that produces a level of pigment in epithelial cells is shown through one division. If the homologous chromosomes were to cross over, subsequent duplication of the genetic material could produce daughter cells that are homozygous either for the pigment gene or its recessive allele. Subsequent phenotypes produce a "twin spotting " effect where daughter cells carrying the dominant color gene are darker and daughter cells carrying the recessive allele are lighter than the surrounding cells. In the drawing at the right, no crossing over has occurred. Note that homologues separate from each other
(Mendel's Law of Segregation) and the daughter cells are thus identical to the parental cell. Now click on the button marked C.O. to see the crossover event. This is a timed process and will automatically take you to the next card several seconds after clicking on the C.O button.
