Sex Verification Testing of Athletes

Sex Verification Testing of Athletes Student Worksheet Click & Learn INTRODUCTION This handout complements the Click & Learn “Sex Verification Testing of Athletes.” LESSON PROCEDURE As you proceed through the interactive, follow the instructions and answer the questions in the spaces provided. INTRODUCTION Select the “Introduction” tab and watch the opening video. After watching the video, scroll down and read the text. As you read, click on the underlined terms to learn more about them. When you have finished, answer questions 1-3 below. 1. What evidence provided supports the claim that “A high level of testosterone provides an unfair advantage in women’s athletics”? Is this adequate evidence? Explain your answer. It is true that men usually have higher testosterone levels than women, and testosterone is associated with greater muscle mass and athletic performance. For this reason, female athletes are sometimes tested to ensure their levels remain within a defined range. However, it is impossible for a woman to control the amount of natural testosterone her body produces. Therefore, female athletes who have high levels of naturally occurring testosterone should not be disqualified from competing. While testosterone is an important factor, it is not the sole determining factor of performance. This is simply the nature of highly competitive athletic sports. 2. Click on the term “biological sex.” Describe how biological sex and gender differ from each other. As stated in the activity, "Biological sex is defined by an individual's combination of chromosomes, hormone levels, internal and external reproductive anatomy, and sex characteristics." It is typically considered a binary trait. Biological sex differs from gender, which is based on social and cultural ideas. Gender identity is a fluid concept and refers to the way an individual thinks of themselves. A person's gender identity does not always necessarily match their biological sex. 3. Are sex verification tests of athletes used to determine biological sex or gender? Explain why you selected sex or gender. Tests are conducted on highly performing female athletes to determine their biological sex, not their gender. These tests are used as a qualifying metric to decide whether a particular female athlete can participate in a given athletic event. Biological sex is tested, not gender, because gender cannot be measured in the same way. Gender is a fluid concept based on one's own perception of self and is shaped by the social and cultural factors of the society in which a person lives. HUMAN DEVELOPMENT Click the “Human Development” tab. As you navigate through this section, use the information to answer questions 4-20. 4. Rewrite the following statement to be correct regarding human chromosomes: “All chromosomes are autosomes, and some autosomes are allosomes.” Humans have 22 pairs of autosomes and 1 pair of allosomes "sex chromosomes" which are separate from autosomes. Genetics www.BioInteractive.org Published December 2018 Page 1 of 8 Click & Learn Student Worksheet Sex Verification Testing of Athletes 5. What does the presence of a Barr body indicate? The presence of a Barr body in each cell indicates that the individual has more than one X chromosome. 6. Regarding the SRY gene … a. What does SRY stand for? The term SRY stands for "Sex determining Region Y." b. On which chromosome is the SRY gene normally found? The SRY gene is typically located on the Y chromosome. c. What is the function of the SRY gene? The function of the SRY gene is to serve as the control point for the differentiation of immature gonads into testes. 7. Think about it. If an embryo made testosterone normally but did not have testosterone receptors in any of its cells, would the embryo develop female reproductive structures, male reproductive structures, or no reproductive structures? Explain your answer. The embryo would develop female reproductive structures. Even though testosterone is produced, without receptors the body cannot respond so the default female pathway would occur. 8. Examine the graph showing blood testosterone levels in elite male and female athletes. Fill in the table below to show the range and mode (highest frequency) of testosterone concentration for females and males in this study. Sex Range Low Mode High Females nmol/L nmol/L nmol/L Males nmol/L nmol/L nmol/L 9. Based on the data in the graph of blood testosterone levels in elite male and female athletes, is there a testosterone concentration that can reliably divide females from males? Explain your answer. No, there is not a single testosterone concentration that can reliably divide elite male athletes from elite female athletes. Although males generally have much higher amounts of testosterone, there is some overlap between males and females. Thus, a reliable bifurcation cannot be established. Genetics www.BioInteractive.org Published December 2018 Page 2 of 8 Sex Verification Testing of Athletes Click & Learn Student Worksheet 10. Secondary sex characteristics arise during puberty. What causes these developmental changes? Secondary sex characteristics develop during puberty due to the relative concentrations of estrogen and testosterone and the body's response to these hormones. Males usually produce more testosterone, and females usually produce more estrogen. This is the main driving force for their developmental changes. 11. List two examples of secondary sex characteristics in females and two in males. Two examples of secondary sex characteristics in females are enlargement of the breasts and widening of the hips. Two examples of secondary sex characteristics in males are facial hair growth and deepening of the voice. 12. Are there secondary sex characteristics that could be the basis of a reliable sex determination test? Explain your answer. No, secondary sex characteristics cannot be used as the basis of a reliable sex determination test. This is because they vary widely among individuals and can overlap between males and females. 13. Regarding DSDs … a. What does the abbreviation DSD stand for? The abbreviation DSD stands for differences in sex development. b. How common are DSDs? According to the activity, "As many as 1 in 100 births show some differences from typical development." In addition, DSDs are also called intersex conditions or disorders of sex development. Answer the following questions using the table of DSDs. 14. CYP21A2 gene mutations a. By what mechanism can a mutation in CYP21A2 change testosterone levels? A mutation in CYP21A2 disrupts steroid hormone production, resulting in congenital adrenal hyperplasia and adrenal gland enlargement. Since the adrenal glands produce androgens, this results in excess testosterone and other hormones. The ultimate result is masculinized traits, while female reproductive organs can still remain present. b. What changes in phenotype are typical in people with a CYP21A2 mutation? People with the CYP21A2 mutation typically have ovaries and a uterus, but show masculinized traits such as an enlarged clitoris, a short vaginal canal, and elevated testosterone levels. They may also experience hyperandrogenism and decreased fertility. 15. SRY gene mutations a. How can an error in chromosome segregation during meiosis affect inheritance of the SRY gene? Mutations in the SRY gene can inactivate its function, rendering it ineffective. Additionally, errors in chromosome segregation during meiosis may result in the deletion of the SRY gene from the Y chromosome. Therefore, resulting in no inheritance of the SRY gene. Genetics www.BioInteractive.org Published December 2018 Page 3 of 8 Sex Verification Testing of Athletes Click & Learn Student Worksheet b. What is the effect of a nonfunctional SRY gene on the development of primary sex characteristics? Without a functioning SRY gene, the gonads do not differentiate into testes. c. Which sex is typically assigned at birth to an individual with a mutation that results in a nonfunctional SRY gene? Individuals are typically assigned to a female sex at birth. This is because the individual has female external sex characteristics. 16. XO a. How can an error in chromosome segregation result in Turner syndrome? When an error in chromosome segregation occurs during meiosis, it is due to one X chromosome being complete, while the second X chromosome is either wholly or partially missing. The condition varies significantly between individuals depending on the extent of the error on the second X chromosome. The condition is known as Turner syndrome. b. Can an individual with Turner syndrome have biological children? Since these individuals have absent or reduced secondary sex characteristics, they are typically infertile. In some individuals, they lack specific reproductive organs such as ovaries. Even if they do have ovaries, they may be non-functional and not synonymous with the creation of life. Therefore, no individual with Turner syndrome can have biological children. 17. AR gene mutation a. Which phenotypes may arise in an individual with a mutation in the AR gene? Individuals may present with female or ambiguous external genitalia, along with male or vague internal reproductive structures; breast development is also possible. These individuals are typically assigned female at birth, but their physical traits vary across a spectrum depending on the specific AR gene mutation involved. b. In humans, the AR gene is located on the X chromosome. If a person who is XY has a complete deletion of the AR gene, do you think giving them testosterone injections during puberty would cause an increase in expression of male secondary sex characteristics compared to not receiving injections? Explain your answer. No, this would not result in the expression of male secondary sex characteristics. With a complete deletion of the AR gene, the cells of the human body lack the functional androgen receptor. Therefore, even if exogenous or external testosterone was injected into an individual who suffered from this condition. That individual's body would not be able to effectively utilize said testosterone since they do not have the appropriate receptor. 18. XXY a. Which of the following terms describes the process of homologous chromosomes failing to separate correctly during meiosis? C. Ametaphasia A. Chromatid adhesion syndrome D. Anti-anaphase B B. Nondisjunction b. If a person with Klinefelter’s syndrome wanted to look more like an average male, what medical treatment could help accomplish this? Medical treatments that could help individuals who suffer from Klinefelter's syndrome are treatments such as testosterone replacement therapy. Testosterone replacement therapy would help develop and promote more typical male secondary sex characteristics. Additionally, this would help with overall health. Genetics www.BioInteractive.org Published December 2018 Page 4 of 8 Sex Verification Testing of Athletes Click & Learn Student Worksheet 19. SRD5A2 gene mutation A mutation of the SRD5A2 gene causes a deficiency in the enzyme 5-alpha reductase. Describe how this affects … a. embryonic development Embryonic development is significantly affected by the SRD5A2 gene mutation. The embryos do not produce enough of the hormone known as dihydrotestosterone. Dihydrotestosterone is essential because it is responsible for male sex development in embryos. b. external reproductive anatomy at birth The SRD5A2 gene mutation results in female or ambiguous external reproductive anatomy at birth. Additionally, it results in male internal reproductive anatomy. c. secondary sex characteristics at puberty The SRD5A2 gene mutation causes a surge in testosterone at puberty. This effect results in an individual mainly having male sex characteristics. Additionally, they can be assigned either female or male at birth. However, the individual may elect to change or reassign their sex after reaching sexual maturity. 20. AMH or AMHR2 gene mutations a. What typically happens to the Müllerian ducts in females during development? b. What typically happens to the Müllerian ducts in males during development? c. Which internal reproductive structures would a person with a mutation in the AMH or AMHR2 gene have? Genetics www.BioInteractive.org Published December 2018 Page 5 of 8 Sex Verification Testing of Athletes Click & Learn Student Worksheet CASE STUDIES Click the “Case Studies” tab, read about the two athletes and the history of sex verification tests, and then use the information to answer questions 21-22. 21. Click the "Sprinter" tab. a. Which four tests have historically been performed to determine an athlete’s biological sex? b. What is a genotype that would explain the sprinter’s phenotype? Explain. 22. Click the "Swimmer" tab. Under current regulations, would the swimmer be allowed to compete? Explain. EXTENSION ACTIVITY DSD TABLE The table on the following page provides additional information on the DSDs shown at the bottom of the Human Development tab. Complete the table to indicate whether a “sex verification test” of a person with each listed DSD would show Barr bodies or the SRY gene, whether their testosterone level would be low (typical of a female) or high (typical of a male), and whether they are likely to menstruate or be fertile (able to have biological children without in vitro fertilization or other medical interventions). Genetics www.BioInteractive.org Published December 2018 Page 6 of 8 Chromosomes Genetic mutation Syndrome Internal reproductive anatomy External genitalia Secondary sex characteristics Sex typically assigned at birth 46,XX None None Female Female Female Female 46,XX CYP21A2 mutation or deletion Congenital adrenal hyperplasia Female Ambiguous Male but reduced Female 46,XY SRY mutation or deletion Swyer syndrome Female but nonfunctional ovaries Female Absent or female, but reduced Female 45,X Complete or partial loss of X chromosome Turner syndrome Female but absent or nonfunctional ovaries Female Absent or female, but reduced Female 46,XY Androgen receptor (AR) deletion Complete androgen insensitivity syndrome Shortened vaginal canal and testes, no fallopian tubes or uterus. Female Female Female 47,XXY Extra X chromosome Klinefelter syndrome Male Male Male but reduced. Breast growth may occur Male 46,XX SRY gene translocation to X XX male syndrome Male Male but small testes Male but reduced Male 46,XY SRD5A2 mutation or deletion 5-alpha reductase deficiency Male Female or ambiguous Male Female No 46,XY Mutation or deletion of the genes for AMH or AMH receptor (AMHR2) Persistent Müllerian duct syndrome Male reproductive organs plus uterus and fallopian tubes Male, but one or both testes may be undescended Male Male No 46,XY None None Male Male genitalia Male Male Genetics www.BioInteractive.org Barr body (Y/N) SRY gene (Y/N) Testosterone (Low/High) Menstruation (Y/N) Fertile (Y/N) Published December 2018 Page 7 of 8 Sex Verification Testing of Athletes Click & Learn Student Worksheet EXTENSION ACTIVITY Four factors are considered when determining a person’s biological sex: 1) chromosomes, 2) hormones, 3) primary sex characteristics that are features essential for sexual reproduction (internal reproductive structures and external genitalia), and 4) secondary sex characteristics, features that typically appear during puberty and are different between the sexes, but are not directly involved in reproduction (for example, females typically have enlarged breasts and widened hips; and males typically have increased facial and body hair, increased muscle mass, and a larger Adam’s apple). Given that the top male athletes outcompete the top female athletes by about 10% in most sports, provide a justification for how each of these four factors is or is not likely to contribute to performance differences between sexes. Factor that helps determine biological sex Likely to affect athletic Justification performance? (Y/N) Chromosomes Hormones Primary sex characteristics Secondary sex characteristics Genetics www.BioInteractive.org Published December 2018 Page 8 of 8