Sexlinked Traits and Disorders Some traits have their

Sex-linked Traits and Disorders

• Some traits have their genes on the X or Y chromosome.

• This is called a sex-linked gene because it is on our sex determining chromosomes.

Regular vision vs. red green colorblindness

There are different forms of colorblindness

• The gene causing color blindness is found on the X chromosome. What do you see in the circle? People with normal vision will see a 6 People with red-green color blindness will see spots

http: //www. colbli ndor. com/colorarrangementtest/ Click for answers

• It is a recessive disorder, you have to have both recessive alleles to be color blind. • However, males only have one X, so if they get one copy, they are colorblind. XX = normal female XY = normal male X*X = carrier female, normal vision X*X* = color blind female X*Y = color blind male

Try it: • Cross a carrier female with a normal vision male. X*X XY Female genotype____ Male genotype ___ X* X Offspring: 25% carrier F X Y X*X X*Y XX XY 25% normal F 0% color blind F 25% color blind M 25% normal M

What parents would make a color blind female? • X*X mom and X*Y dad X* Y X* X*Y X X*X XY https: //www. youtube. com/watch? v=i. Uj 7 y 7 eqzk. U What causes colorblindness? https: //www. youtube. com/watc h? v=m 1 X 0 QTTt. Pmc Colorblind brothers see color

Hemophilia is also sex-linked in humans. • Hemophilia is a bleeding disorder in which it takes a long time for blood to clot. http: //www. ncbi. nlm. nih. gov/pubmedhealth/PMH 0001564/

• Females can be normal (XX), carriers (X*X), or have hemophilia (X*X*). • Males can either have it (X*Y) or not (XY), they cannot be a carrier.

• Because hemophilia is sex-linked, it is seen in males (1 in 10, 000) more often than in females (1 in 100, 000).

Historical Connection: This disorder was seen in the British royal family and a number of princes died at a young age due to the disease.

Try it: Cross a man with hemophilia with a woman who is a carrier. X*Y Female genotype ___ X*X Male genotype ___ X* Y X* X*Y X X*X XY Offspring: 25% carrier F 0% normal F 25% hemophilia M 25% normal M 25% hemophilia F

Review • https: //www. youtube. com/watch? v=h 2 xufr HWG 3 E