Discussion Assignment #1

The Birds and the Bees

There's a lot more to sex determination than most people think. We're all very familiar with the system found in mammals: normal females have two X chromosomes, normal males have one X and one Y. The key to this is the Y chromosome: in mammals, the presence of a properly functioning Y chromosome creates a male.

But other kinds of animals utilize different sex determining systems. Your task for this week is to investigate this phenomenon.

The chromosomal basis of gender was actually discovered in Drosophila melanogaster (fruit flies). However, it turns out that, though these insects do have an XX/XY system, it doesn't actually work the same as the mammalian system. Your first task is to discover how the Drosophila system actually works.

After you've figured out how the fruit flies do it, consider the issue of chromosome anomalies. Errors in sex chromosome numbers are relatively common, compared to errors in other chromosome numbers. Fill out the blank spaces in the following chart with "male" or "female," depending upon whether the particular chromosome complement would produce a male or a female mammal or fruit fly.

Finally, investigate gender determination in the following kinds of animals:

Fish (not all are the same--have fun!)
Honey Bees

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