This work was created by Dr Jamie Love and Creative Commons Licence licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

Self Assessment Questions for Lesson 12

Sex Determination, Chromosomes and Mosaicism

by Dr Jamie Love Creative Commons Licence 2002 - 2005

#1

What is the difference between monoecious and dioecious?

What word is sometimes used for a monoecious animal?

Is the sex of all organisms determined by genetics?

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#2

What is the difference between an autosome and a sex chromosome, how are they designated and how many of each does a normal person have?

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#3

Give the chromosome count (total number of chromosomes), the sex chromosomes compliment (X, Y and numbers of each) and number of Barr bodies (inactivated X chromosomes) would you find in:

  1. a normal man?
  2. a normal woman?
  3. someone with (standard) Klinefelter syndrome?
  4. someone with XYY syndrome?
  5. someone with Turner syndrome?
  6. someone with Trisomy syndrome?

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#4

(True story.)
A veterinarian was presented with a calico cat. You may recall that the calico pattern of these cats is caused by the mosaic X inactivation patterns for genes involved in coat color. To the vet's surprise, the cat was a "tom" (a male cat)!

Is that normal?

How could that happen?

Hint - the vet solved the mystery by checking the cat's karyotype. What do you think was discovered about this cat's chromosomes?

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#5

Assume a human sperm cell, carrying 22 autosomes and both an X chromosome and a Y chromosome, fuses with a normal human egg carrying 23 chromosomes, including the X chromosome.

What will be the sex of the child?

How many Barr bodies, if any, will the child have?

If that child were able to make gametes - s/he cannot, but assume s/he can - what combination of sex chromosomes would be possible in the gametes. (Ignore the autosomes, just tell me what sex chromosomes could be in the gametes.)

What would be the composition of each zygote produced if each gamete, above, fertilized another gamete with an X chromosome and the normal complement of 22 autosomes?

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This work was created by Dr Jamie Love and Creative Commons Licence licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.