Reference no: EM132633377
Name Sex Testing of Athletes Worksheet
Go to the HHMI Biointeractive Sex Testing of Athletes virtual lab at https://media.hhmi.org/biointeractive/click/testing-athletes/ Start by watching the introductory video and reading the "Human Development" section outlining ways in which human sexual development can lead to a range of phenotypes. Based on what you read in this section, answer the following questions:
1. Why does a Barr body form in some cells? What does its presence indicate about the sex chromosomes in that cell?
Barr corpuscles also called Barr bodies are a dense mass of highly condensed chromatin that is observed in the nucleus of somatic cells of women, these corpuscles are a kind of remnant of the X chromosome that has undergone the process called chromosome inactivation X which occurs randomly (that is, in either of the two X chromosomes of a woman) during embryonic development of female individuals in order to achieve a compensation of the genetic dose with respect to the genes located in the X chromosome in women.
Therefore, the presence of a Barr corpuscle in a cell tells us that its sex chromosomes are two X chromosomes, that is, XX.
2. What is the role of the SRY gene? Where is it located?
The SRY gene Sex determining region of the Y chromosome is located on the short arm of the Y chromosome, that is, under normal conditions it is only present in male individuals, this gene encodes a protein called testis-determining factor that is responsible for triggering a series of processes at the cellular level that have as a consequence the formation or differentiation of the testes from the germ cells of the genital organs.
3. Examine the graph of blood testosterone in athletes.
What is the range (lowest value to highest value) of testosterone levels measured for self-identified female athletes?
According to the Two large-scale studies of testosterone levels in athletes have been conducted, and they provide different results. The one shown here reported that 13.7% of female athletes have testosterone levels above the typical female range. The second study (Bermon, S. et al. J. Clin. Endocrinol. Metab. 99: 4328, 2014), which did not include any male athletes, reported that only 1.5% of female athletes have testosterone levels above the typical female range. Differences in how the measurements were taken and the athletes who were included may explain the differences in results.
b. What is the range of testosterone levels measured for self-identified male athletes?
c. What does this graph tell you about the potential issues with measuring testosterone in athletes?
As can be seen on the graph, there is not a testosterone concentration that can reliably divide females from males as there were still female outliers in the data that had higher testosterone concentration than others.
Complete the "Case Studies" section outlining cases of athlete sex testing.
1. In the case of the sprinter, what is the most likely genotype from the table above that fits with the athlete's test results?
Explain your answer.
The phenotype of the sprinter is most consistent with a 46, XY individual with androgen insensitivity. Without a functioning androgen receptor, testosterone does not affect cells and so the individuals with this condition have a functioning SRY gene, high testosterone levels and no bar bodies.
2. In the case of the swimmer, what is the most likely genotype from the table above that fits with the athlete's test results? Explain your answer.
Under current regulations the swimmer would be allowed to compete as her testosterone levels are low.
3. Is there a single test that can divide humans into two categories with respect to sexual development? Explain why or why not.