1. Sex Determination, pedigrees and more

2. I. Sex Determination in Humans
General Information
1. 23 chromosomes come from Mom
2. 23 chromosomes come from Dad
3. 23rd pair of chrs. Is XX if ♀
4. 23rd pair of chrs. Is XY if ♂

3. ★Total # of chrs. In normal human = 46
I. Non-sex chrs. (autosomes)
2. Sex chrs.

4. B. Details of Sex determination
Having a Y chr. makes a ♂ child
Absence of an X chr. Is fatal
♂s make X & Y sperm

5. B. Details of Sex determination
4. If X sperm fertilizes egg, then ♀ child
5. If Y sperm fertilizes egg, then ♂ child
★Therefore, ♂ determines the sex of the child

6. II. Pedigrees
= diagram showing the inheritance of a certain gene through several generations
Symbols ♀ ♂
breeding
breeding
offspring

7. III. Sex-linked traits Usually found on X chromosome
Affects males more than females
Females can be carriers, & not have the disorder (but can pass it to offspring)
Examples: color blindness and hemophilia

8. IV. Hemophilia Background Facts 1. Bleeding disorder
2. Caused by lack of clotting factor
3. Slight injury or nose-bleed can be fatal

9. IV. Hemophilia 4. Recessive sex-linked genetic disease
5. Info. on X chromosome (no info. On Y)

10. II. History One of Victoria’s Secrets… Queen Victoria of England
was a carrier
of hemophilia
Victoria, age 16

11. II. History

12. Queen Victoria’s Family 1881
II. History
Queen Victoria’s Family 1881

13. Queen Victoria’s descendants

14. Alexei Romanov, son of Tsar Nicolas II
One of the most famous hemophiliacs was Russian Prince Tsarevitch Alexei, killed along with all his family during the Russian revolution in 1917.

15. Treatment Transfusions w/ clotting factor VIII Danger: HIV & other
blood-borne
pathogens

16. Hemophilia problem Alice is a carrier
Her husband does not have the disorder.
Can their children have the disorder?
Yes!
Let’s use a Punnett square to determine the probabilities. X

17. Hemophilia problem X Y Xh