Presentation is loading. Please wait.

Presentation is loading. Please wait.

1 Cross-Dressing or Crossing-Over: Sex Testing of Women Athletes Maureen Knabb, Department of Biology, West Chester University, and Joan Sharp, Biological.

Similar presentations


Presentation on theme: "1 Cross-Dressing or Crossing-Over: Sex Testing of Women Athletes Maureen Knabb, Department of Biology, West Chester University, and Joan Sharp, Biological."— Presentation transcript:

1 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 2 Santhi’s Story /how-are-athletes- gender-tested.html

3 3 Santhi’s Story Santhi Soundararajan won the silver medal in the 800-meter race at the 2006 Asian Games in Doha, Qatar.

4 4 Santhi’s Story Following her silver medal performance, her sex was officially questioned.

5 5 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.

6 6 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.

7 7 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.

8 8 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.

9 9 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.

10 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: A: Male B: Female

11 11 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

12 12 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.

13 13 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.

14 14 What does an individual chromosome look like? During nuclear division, DNA is tightly packed. This chromosome is composed of 2 chromatids. In this diagram, the DNA has replicated (more on this later).

15 15 Karyotype In diploid organisms, chromosomes come in pairs. How many? Human Karyotype (picture of chromosomes in a cell)

16 16 Karyotype In diploid organisms, chromosomes come in pairs (e.g., 23 pairs for humans). How do you make a karyotype? Human Karyotype (picture of chromosomes in a cell)

17 17 CQ2: A karyotype was performed on a different athlete. Here are the results: From these results, the athlete is: A: Male B: Female

18 18 CQ2: A karyotype was performed on an athlete. Here are the results: From these results, the athlete is: Male

19 19 CQ3: So if Santhi is a normal female, her karyotype would be: A: XX B: XY C: YY D: XXY

20 20 CQ3: So if Santhi is a normal female, her karyotype would be: A: XX

21 21 SEX (Do I have your attention now?)

22 22 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?

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

24 24 Haploid and Diploid Chromosomes Haploid with two chromatidsHaploid with one chromatid Diploid with one chromatidDiploid with two chromatids

25 25 CQ4: Assume that this is one of Santhi’s chromosomes. This chromosome is composed of two chromatids joined by a centromere. Are the following statements TRUE or FALSE?

26 26 A.These chromatids make up a diploid chromosome. False

27 27 B. The cell that contains these sister chromatids must be diploid. False

28 28 C. The sister chromatids were formed by replicating a single chromatid. True

29 29 D. The sister chromatids were joined by fertilization, bringing together a maternal and paternal chromatid. False

30 30 Meiosis Purpose of meiosis: –in animals, to produce gametes with just half the parents’ genetic material. Gametes are _____(haploid/diploid). Haploid

31 31 Meiosis Mechanism: Only one of each pair of homologous chromosomes gets into each gamete. The happy ending: Gametes from the two parents get to fuse, restoring the original number of chromosomes in the fertilized egg (zygote).

32 32 Stages of Meiosis Meiosis (in animals) produces 4 haploid cells from 1 diploid cell. At the end of the first division (Meiosis I) the 2 cells are already haploid. The second division (Meiosis II) splits the 2 sister (identical, replicated DNA) chromatids to 1 chromatid. Animation:

33 33 CQ5: Which one is true after Meiosis I? A: Four cells have been produced. B: The cells are haploid. C: The DNA will be replicated once more. D: The cells are ready to perform as gametes. E: Each chromosome consists of a single strand of DNA.

34 34 CQ5: Which one is true after Meiosis I? B: The cells are haploid.

35 35 CQ6: During Meiosis II: A: Homologous chromosomes separate. B: The DNA is replicated. C: Gametes fuse. D: Sister chromatids separate. E: All of the above.

36 36 CQ6: During Meiosis II: D: Sister chromatids separate.

37 37 Sources of Genetic Variability in Meiosis Independent Assortment Each pair of homologous chromosomes lines up at Metaphase I plate.

38 38 Sources of Genetic Variability in Meiosis Independent Assortment There is a 50:50 chance that a daughter cell will get one or the other copy of the chromosome. Animation:

39 39 CQ7: How many possible combinations of maternal chromosomes are possible in a human ovum due to independent assortment during meiosis? A: 23 combinations. B: 46 combinations. C: 23 2 = 529 combinations. D: 2 23 = ~ 8 million combinations.

40 40 CQ7: How many possible combinations of maternal chromosomes are possible in a human ovum due to independent assortment during meiosis? D: 2 23 = ~ 8 million combinations.

41 41 Sex Determination In mammals, males have one X and one Y chromosome. In males, half the daughter cells formed by Meiosis I get an X chromosome and half get a Y chromosome. Following Meiosis II and sperm differentiation, half the sperm are X-bearing and half are Y- bearing.

42 42 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.

43 43 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.

44 44 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 egg XXXY XXXY girlsboys X X Y X

45 45 How is Sex Determined in Humans? Sex is determined by the sex chromosome carried by the sperm. What sex chromosome is carried by the egg? sperm egg XXXY XXXY girlsboys X X Y X

46 46 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.

47 47 CQ8: Could Santhi have an XX karyotype and be male? We will see…

48 48 Sources of Genetic Variability in Meiosis When homologous chromosomes pair during meiosis, non-sister chromatids exchange homologous portions. Crossing Over During Meiosis

49 49 Sources of Genetic Variability in Meiosis A chiasma forms between the non- sister chromatids at the point of crossing over. Crossing Over During Meiosis

50 50 Sources of Genetic Variability in Meiosis Following crossing over, the chromatids are recombinant, combining paternal and maternal genes. Crossing Over During Meiosis

51 51 Crossing Over Crossing over can occur anywhere along the autosomes. In males, the sex chromosomes (X and Y chromosomes) normally cross over only at their tips if at all.

52 52 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.

53 53 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)

54 54 How is Sex Characterized in Humans? Anatomy –What they look like, genitals Physiology – hormones Chromosomes- XX or XY But there is a 4 th answer: Genes Specific genes determine whether an embryo will develop as a male or female.

55 55 SRY Gene Early in development, the immature gonads of males and females are indistinguishable. SRY gene X Y (Sex-Determining Region of the Y chromosome)

56 56 SRY Gene Males: In the 7 th week of development, the SRY gene on the Y chromosome activates a number of genes, and the gonads develop as testes. SRY gene X Y (Sex-Determining Region of the Y chromosome)

57 57 SRY Gene Females: With no SRY gene, gonads develop as ovaries by default. SRY gene X Y (Sex-Determining Region of the Y chromosome)

58 58 Can you have an XX male or XY female? Watch this video: What sex is XX (SRY+)? What sex is XY (SRY-)? Sex reversal occurs in 1 in 20,000 births!

59 59 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.

60 60 CQ11: What do you think about requiring gender testing for female athletes in international competition?

61 61 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.

62 62 What about Santhi Soundararajan? Santhi was stripped of her silver medal.

63 63 What about Santhi Soundararajan? An anonymous official in the know has reported that Ms. Soundarajan's tests revealed more Y chromosomes than are usually present in the genetic make-up of a female. No official statement has been made.

64 Assignment Write a paragraph, stating your opinion on how, or if Olympian athletes should be tested, and which methods should not be used. Use the words sexual characteristics, chromosome, and SRY gene. Use this paragraph to prove your knowledge on sex determination. You will not be graded on your opinion, but how you defend that opinion. 64


Download ppt "1 Cross-Dressing or Crossing-Over: Sex Testing of Women Athletes Maureen Knabb, Department of Biology, West Chester University, and Joan Sharp, Biological."

Similar presentations


Ads by Google