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Cross-Dressing or Crossing-Over: Sex Testing of Women Athletes

Cross-Dressing or Crossing-Over: Sex Testing of Women Athletes. Maureen Knabb, Department of Biology, West Chester University, and Joan Sharp, Biological Sciences, Simon Fraser University Modified by Penny Dunning, EHS. Santhi’s Story.

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Cross-Dressing or Crossing-Over: Sex Testing of Women Athletes

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  1. Cross-Dressing or Crossing-Over: Sex Testing of Women Athletes Maureen Knabb, Department of Biology, West Chester University, and Joan Sharp, Biological Sciences, Simon Fraser University Modified by Penny Dunning, EHS

  2. Santhi’s Story Santhi Soundararajan won the silver medal in the 800-meter race at the 2006 Asian Games in Doha, Qatar.

  3. Santhi’s Story Following her silver medal performance, her sex was officially questioned.

  4. 18 Dec. 2006: “Indian athlete Santhi Soundararajan fails gender test” • Top Indian woman athlete Santhi Soundararajan, who won a silver medal at a recent regional championship, has failed a gender test, according to official reports.

  5. 18 Dec. 2006: “Indian athlete Santhi Soundararajan fails gender test” • Sports writer KP Mohan said that a team of doctors, including a gynecologist, endocrinologist and psychologist, normally examines athletes and puts them through physical and clinical examinations during a gender test.

  6. 18 Dec. 2006: “Indian athlete Santhi Soundararajan fails gender test” • Santhi Soundararajan's test was done soon after Soundararajan came in second in the women's 800m race on 9 December, but it is not clear how she failed the test at the Asian Games in Doha.

  7. How do you know if someone is male or female? • Talk to the person next to you and identify at least 5 characteristics to distinguish males from females.

  8. How is sex determined in humans? • Anatomy: Primary and secondary sexual characteristics - genitalia, body hair, pelvis, etc. • Physiology: Function and interaction of the sex organs including concentrations of sex hormones such as estrogen, progesterone, and testosterone.

  9. CQ1: Imagine you are a member of the committee assigned to determine whether Santhi is female. Here are possible results of the initial tests (we don’t know the real results): Female genitalia: Yes Breasts and pubic hair: Yes Regular menstrual cycle: Never From this information, you conclude that Santhi is: A: Male B: Female

  10. CQ1: Imagine you are a member of the committee assigned to determine whether Santhi is female. Here are possible results of the initial tests (we don’t know the real results): Female genitalia: Yes Breasts and pubic hair: Yes Regular menstrual cycle: Never From this information, you conclude that Santhi is: B: Female

  11. Is there another way that sex is characterized in humans? • Chromosomes: • Females possess two X chromosomes in each of their cells, • Males have one X and one Y chromosome.

  12. Is there another way that sex is characterized in humans? • How do you visualize chromosomes? • Chromosomes are only visible when preparing for nuclear division. • Chromosomes must be stained.

  13. Karyotype In diploid organisms, chromosomes come in pairs. How many? 0 (picture of chromosomes in a cell) Human Karyotype

  14. CQ2: A karyotype was performed on a different athlete. Here are the results: From these results, the athlete is: A: MaleB: Female

  15. CQ2: A karyotype was performed on an athlete. Here are the results: From these results, the athlete is: Male

  16. CQ3: So if Santhi is a normal female, her karyotype would be: A: XX B: XY C: YY D: XXY

  17. CQ3: So if Santhi is a normal female, her karyotype would be: A: XX

  18. 0 The Fate of Genetic Material During Sexual Reproduction • You contain genetic material from both your Mom and Dad. • You have 46 chromosomes, and so do (will) your children. • How does this happen?

  19. SEX Mom 46 chromosomes Dad (2n = diploid) Egg 23 chromosomes Sperm (1n = haploid) Zygote (fusion) 46 chromosomes again!

  20. Sex Determination • In mammals, males have one X and one Y chromosome. • A special cell division called Meiosis will form gametes (sperm) • Half their sperm are X-bearing and half are Y-bearing.

  21. Sex Determination • In mammals, females have two X chromosomes. • A special cell division called Meiosis will form gametes (eggs) • All eggs are are X-bearing.

  22. How is Sex Determined in Humans? • Sex is determined by the sex chromosome carried by the sperm. • What percent of offspring will be boys and what percent will be girls? sperm X Y X XX XY egg XX XY X girls boys

  23. CQ8: Could Santhi have an XX karyotype and be male? A: No, an XX individual is always female. B: Yes, this is common. C: Yes, if a male-determining control gene is carried on one of her X chromosomes.

  24. CQ8: Could Santhi have an XX karyotype and be male? We will see…

  25. Sources of Genetic Variability in Meiosis Crossing Over During Meiosis • When homologous chromosomes pair during meiosis, non-sister chromatids exchange homologous portions.

  26. Sources of Genetic Variability in Meiosis Crossing Over During Meiosis • A chiasma forms between the non-sister chromatids at the point of crossing over.

  27. Sources of Genetic Variability in Meiosis Crossing Over During Meiosis • Following crossing over, the chromatids are recombinant, combining paternal and maternal genes.

  28. Crossing Over • Crossing overcan occur anywhere along the autosomes. • In males, the sex chromosomes (X and Y chromosomes) normally cross over only at their tips if at all.

  29. CQ9: During crossover, all of the following happen EXCEPT: A: The homologous chromosomes line up in pairs. B: The homologous chromosomes swap pieces with their adjacent partners. C: Crossing over decreases the genetic variability in the gametes. D: Each chromatid is unique after it has crossed over.

  30. CQ9: During crossover, all of the following happen EXCEPT: C: Crossing over decreases the genetic variability in the gametes. (Crossing over actually INCREASES the genetic variability in the gamets)

  31. How is Sex Characterized in Humans? • Anatomy –What they look like, genitals • Physiology – hormones • Chromosomes- XX or XY • But there is a 4th answer: Genes Specific genes determine whether an embryo will develop as a male or female.

  32. SRY Gene (Sex-Determining Region of the Y chromosome) • Early in development, the immature gonads of males and females are indistinguishable. SRY gene Y X

  33. SRY Gene (Sex-Determining Region of the Y chromosome) • Males: In the 7th week of development, the SRY gene on the Y chromosome activates a number of genes, and the gonads develop as testes. SRY gene Y X

  34. SRY Gene (Sex-Determining Region of the Y chromosome) • Females: With no SRY gene, gonads develop as ovaries by default. SRY gene Y X

  35. Can you have an XX male or XY female? • Watch this video: http://www.hhmi.org/biointeractive/media/meiosis-lg.mov • What sex is XX (SRY+)? • What sex is XY (SRY-)? Sex reversal occurs in 1 in 20,000 births!

  36. CQ10: If you were a member of the Asian Games medal committee and Santhi’s karyotype revealed that she is XY and SRY-, what would you do? A: She has female genitalia, allow her to keep her medal. B: She is genetically (according to her chromosomes, but not SRY gene) male, take her medal away. C: Perform additional tests.

  37. CQ11: What do you think about requiring gender testing for female athletes in international competition?

  38. A: It should be banned because gender determination is so complex. B: It is necessary to ensure an even playing field. C: It is necessary, but needs to include a large number of genetic tests to ensure fairness. D: It should be required for all athletes, both male and female.

  39. What about Santhi Soundararajan? Santhi was stripped of her silver medal.

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