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

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

• Modified from Maureen Knabb, Department of
  Biology, West Chester University, and Joan Sharp,
  Biological Sciences, Simon Fraser University

2
Gender Testing in Sports

• Do a quick internet search to find out more
  information about the history of female gender
  testing in athletics.

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Santhis Story

• http//www.ibnlive.com/videos/28851/how-are-athle
  tes-gender-tested.html

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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.
• 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.
• 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.

5
How do you know if someone is male or female?

• Identify at least 5 characteristics to
  distinguish males from females in your small
  group.

6
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.

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Q1 Imagine you are a member of the committee
assigned to determine whether Santhi is female.
Here are possible results of the initial tests
(we dont 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

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Is there another way that sex is characterized in
humans?

• Chromosomes
• Females possess two X chromosomes in each of
  their cells, whereas males have one X and one Y
  chromosome.
• How do you visualize chromosomes?
• Chromosomes are only visible when preparing for
  nuclear division.
• Chromosomes must be stained.

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What does an individual chromosome look like?
0

• 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).

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Karyotype(picture of chromosomes in a cell)
0
Human Karyotype

• In diploid organisms, chromosomes come in pairs
  (e.g., 23 pairs for humans).
• How do you make a karyotype?
• http//learn.genetics.utah.edu/units/disorders/kar
  yotype/karyotype.cfm

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Q2 A karyotype was performed on an athlete.
Here are the results

• From these results, the athlete is
• A Male B Female

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Q3 So if Santhi is a normal female, her
karyotype would be

• A XX
• B XY
• C YY
• D XXY

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SEX(Do I have your attention now?)
0
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The Fate of Genetic Material During Sexual
Reproduction
0

• You contain genetic material from both your Mom
  and Dad.
• You have 46 chromosomes, and so do (will) your
  children.
• How does this happen?

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SEX

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

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Haploid and Diploid Chromosomes
Haploid with two chromatids
Haploid with one chromatid
Diploid with one chromatid
Diploid with two chromatids
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Q4 Assume that this is one of Santhis
chromosomes. This chromosome is composed of two
chromatids joined by a centromere.

• A These chromatids make up a diploid chromosome.
• B The cell that contains these sister chromatids
  must be diploid.
• C The sister chromatids were formed by
  replicating a single chromatid.
• D The sister chromatids were joined by
  fertilization, bringing together a maternal and
  paternal chromatid.

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Meiosis
0

• Purpose of meiosis in animals, produce gametes
  with just half the parents genetic material.
• Gametes are ______ (haploid/diploid).
• 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).

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Stages of Meiosis
0

• 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 http//www.johnkyrk.com/meiosis.html
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Q5 What is true after Meiosis I?

0

• 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.

161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180
181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200
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Q6 During Meiosis II

0

• A Homologous chromosomes separate.
• B The DNA is replicated.
• C Gametes fuse.
• D Sister chromatids separate.
• E All of the above.

161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180
181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200
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Sources of Genetic Variability in Meiosis

• Independent Assortment
• Each pair of homologous chromosomes lines up at
  Metaphase I plate.
• There is a 5050 chance that a daughter cell will
  get one or the other copy of the chromosome.

Animation http//wps.prenhall.com/wps/media/objec
ts/487/498795/CDA10_2/CDA10_2b/CDA10_2b.htm
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Q7 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 232 529 combinations.
• D 223 8 million combinations.

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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.

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How is Sex Determined in Humans?
sperm

• Sex is determined by the sex chromosome carried
  by the sperm.
• What sex chromosome is carried by the egg?

X
Y
X
XX
XY
egg
XX
XY
X
girls
boys
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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.

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Sources of Genetic Variability in Meiosis

• Crossing Over During Meiosis
• When homologous chromosomes pair during Prophase
  I, non-sister chromatids exchange homologous
  portions.
• A chiasma forms between the non-sister chromatids
  at the point of crossing over.
• Following crossing over, the chromatids are
  recombinant, combining paternal and maternal
  genes.

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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.

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Q9 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.

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How is Sex Characterized in Humans?

• In addition to anatomy, physiology, and
  chromosomes, there is a 4th answer
• Genes Specific genes determine whether an
  embryo will develop as a male or female.

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SRY (Sex- Determining Region of the Y chromosome)
Gene

• Early in development, the immature gonads of
  males and females are indistinguishable.
• 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.
• Females With no SRY gene, gonads develop as
  ovaries by default.

SRY gene
Y
X
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Can you have an XX male or XY female?

• Watch this video http//www.hhmi.org/biointeracti
  ve/media/meiosis-lg.mov
• What sex is XX (SRY)?
• What sex is XY (SRY-)?
• Sex reversal occurs in 1 in 20,000 births!

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Q10 If you were a member of the Asian Games
medal committee and Santhis 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 male, take her medal away.
• C Perform additional tests.

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Q11 What do you think about requiring gender
testing for female athletes in international
competition?

• 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.

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

• Use the following link to review the process of
  gender testing in athletes
• Gender Testing of Female Athletes