Sex Determination, pedigrees and more

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 ♂

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

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

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

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

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

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

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

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

II. History

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

Queen Victoria’s descendants

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.

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

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

Hemophilia problem X Y Xh