Virtual Lab: Sex-Linked Question: How can sex - linked traits be identified?

Virtual Lab: Sex-LinkedWebsite: http://glencoe.mheducation.com/sites/dl/free/0078802849/383935/BL_15.htmlQuestion: How can sex - linked traits be identified?Background:Sex-linked traits are characteristics carried on genes of the sex chromosomes. Thomas Hunt Morgan wasone of the first scientists known to observe sex linkage. In his experiments with the common fruit fly,Drosophila melanogaster, he analyzed the results of the following Drosophila mating:1. A white-eyed male crossed with a red-eyed female produced all red-eyed F1 offspring, as expectedaccording to Mendelian laws of inheritance. An F1 red-eyed male crossed with an F1 red-eyed femalewould result in 3 red-eyed F2 offspring (male or female): 1 white-eyed F2 offspring (male or female)according to Mendelian laws of inheritance. But Morgan found that all of the F2 female offspring andhalf of the F2 male offspring had red eyes, which is not expected according to Mendelian laws ofinheritance.A white-eyed female crossed with a red-eyed male resulted in all of the F1 female offspring having redeyes and all of the F1 male offspring having white eyes, which is expected according to Mendelian lawsof inheritance. An F1 red-eyed female crossed with an F1 white-eyed male would result in 3 red-eyed F2offspring (male or female): 1 white-eyed F2 offspring (male or female) according to Mendelian laws ofinheritance. But Morgan found that half of the F1 offspring of each sex had red eyes and the other halfhad white eyes, which is not expected according to Mendelian laws of inheritance.2. Morgan's results proved that more complex laws of inheritance exist. The alleles for Drosophila eye-color are not simply dominant or recessive. Because of the ratios that resulted from his Drosophilacrosses, Morgan concluded that the gene for eye color is carried by, or linked to, the X chromosome. Healso found that the Y chromosome does not carry a gene for this characteristic.Fruit flies are often used to study genetics because of their short life cycle (about 2 weeks), their smallsize (several hundred can be housed in a small jar), and their fecundity (a single pair may produce morethan a hundred offspring).1