Reproductive Case Study 3

Sex Chromosome Variations


The normal genetic make-up of humans is 22 pair of chromosomes referred to as autosomes and one pair of chromosomes called sex chromosomes. The autosomes are the chromosomes that do not carry genes that determine sex. Autosomes carry information for traits such as eye color. The sex chromosomes determine the sex of an individual. All egg cells carry a single X chromosome, and sperm carry either an X chromosome or a Y chromosome. The sex of an individual is determined by whether an X carrying sperm fertilizes the egg or whether a Y carrying sperm fertilizes the egg. In the usual case, genetic females have two X sex chromosomes, and genetic males have an X and a Y chromosome. Variations in the sex chromosomes occur in approximately 1 in 500 – 1,000 live births. There are four different types of sex chromosome variations – XYY, XXX, XXY, and XO. Sex chromosome variations are largely undiagnosed, and are more common than Down syndrome and cystic fibrosis.


Answer the following questions in the fields below.


General Questions

1.)  Desribe the mechanism by which a peptide hormone initiates a cell response; a steroid hormone initiates a cell response. How are they the same? How are they different? Give a specific example of each and state their effect on the human body.

2.) Compare the hormonal controls of the male reproductive cycle with the hormonal controls of the female reproductive cycle.  How are they the same?  How are they different?

Specific Questions

Question 1:  What are the four most common conditions that males with the XXY variation express? What is the XXY sex chromosome variation known as?


Question 2:  When are males with the XXY variation frequently identified?   


Question 3:  It is possible for males with Klinefelter’s syndrome to have more than two X sex chromosomes. What correlation is there between the number of X sex chromosomes and their mental abilities?


Question 4:  What is the sex chromosome make up of an individual with Turner’s syndrome?


Question 5:  What are some physical characteristics of an individual with Turner’s syndrome?


Question 6:  What characteristics do metafemales (also called “super females” or XXX females) usually exhibit?



Question 7:  Describe the characteristics of an XYY male?


Question 8:  Are criminal tendencies associated with the XYY syndrome?


Adapted from: Human Physiology-from cells to systems by Lauralee Sherwood

Thomson/Brooks-Cole Publ. 5th edition 2004