Name ____________________________________________ hour __________ Date __________
Crossing-over XY Chromosomes
1. State 5 characteristics used to distinguish males from females.
a. .
b.
c. .
d. .
e. .
f. .
2. 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
3. Humans have _________ chromosomes or __________ pair.
4. What is the normal karyotype of sex chromosomes for a female?
a. XX
b. XY
c. YY
d. XXY
5. What is the normal karyotype of sex chromosomes for a female?
a. XX
b. XY
c. YY
d. XXY
6. What percent of offspring will be boys and what percent will be girls?
7. True or False - The homologous chromosomes line up in pairs.
8. True or False - The homologous chromosomes swap pieces with their adjacent
partners.
9. True or False - Crossing over decreases the genetic variability in the gametes.
10. True or False - Each chromatid is unique after it has crossed over.
11. How is Sex Characterized in Humans?
a. ________________________ –What they look like, genitals
b. _________________________ – hormones
c. __________________________- XX or XY
d. But there is a 4th answer: ________________________________
12. In Males during the 7th week of development, the ___________ gene on the
___________ chromosome ___________________ a number of genes, and the
_____________________ develop as ____________________.
13. With ______________ SRY gene, gonads develop as ___________________ by default
and the baby will be _________________.
14. After you watch the video, what sex is XX (SRY+)?
XX (SRY-)?
15. After you watch the video, What sex is XY (SRY-)?
XY(SRY+)?
16. Sex reversal occurs in 1 in __________________________ births!
17. 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 the SRY gene)
male, take her medal away.
c. Perform additional tests.
18. What do you think about requiring gender testing for female athletes in
international competition? (circle all that apply)
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
e. I don’t know.
19. Did Santhi get to keep her medal?