Sex-Linked Traits Most traits of the human genome are autosomal traits, which means the alleles for these traits are located on pairs 1 –22. Some traits are inherited on the "X" chromosome of the 23rd pair of sex chromosomes. The "Y" chromosome carries NO alleles for any traits. The trait for colorblindness is caused by a recessive allele on the "X" chromosome. The allele for normal vision is "C" and is dominant over the recessive allele "c".

The answer is 12, people with abnormal vision see 45

The answer is 15, people with abnormal vision see 76

The answer is 6, people with abnormal vision see 8.

The answer is 73, people with abnormal vision see 18.

Trait: Colorblindness Alleles: C =normal vision c = colorblind GenotypesPhenotypes X C X C Female w/normal vision_ X C Y X c X c X C X c (Known as a “".) X c Y

Trait: Colorblindness Alleles: C =normal vision c = colorblind GenotypesPhenotypes X C X C Female w/normal vision_ X C YMale w/ normal vision X c X c X C X c (Known as a “ ".) X c Y

Trait: Colorblindness Alleles: C =normal vision c = colorblind GenotypesPhenotypes X C X C Female w/normal vision_ X C YMale w/ normal vision X c X c Colorblind Female X C X c (Known as a “ ".) X c Y

Trait: Colorblindness Alleles: C =normal vision c = colorblind GenotypesPhenotypes X C X C Female w/normal vision_ X C YMale w/ normal vision X c X c Colorblind Female X C X c Female w/ normal vision (Known as a “carrier".) X c Y

Trait: Colorblindness Alleles: C =normal vision c = colorblind GenotypesPhenotypes X C X C Female w/normal vision_ X C YMale w/ normal vision X c X c Colorblind Female X C X c Female w/ normal vision (Known as a “carrier".) X c YColorblind male

Sample Problems Normal man (___ ___) & Carrier woman (___ ___) What % of offspring will be normal? ____ Colorblind? ______ What % of the females will be normal? ____ Colorblind? _____ What % of the males will be normal? _____ Colorblind? _____ What % will be carriers? _________ If they have a daughter, what is the chance she will be a carrier?_____

Sample Problems Colorblind man (___ ___) & Normal woman (___ ___) What % of offspring will be normal? ____ Colorblind? ______ What % of the females will be normal? ____ Colorblind? _____ What % of the males will be normal? _____ Colorblind? _____ What % will be carriers? _________ If they have a daughter, what is the chance she will be colorblind?_____

Sample Problems Normal man (___ ___) & Colorblind woman (___ ___) What % of offspring will be normal? ____ Colorblind? ______ What % of the females will be normal? ____ Colorblind? _____ What % of the males will be normal? _____ Colorblind? _____ If they have a son, what is the chance that he is colorblind? _____ If they have a daughter, what is the chance she is colorblind?_____ Carrier? __

Questions Is it possible for a man to be a "carrier"? ______ Why? ______________________________

Questions Is it possible for a man to be a "carrier"? NO Why? Because men only have ONE X chromosome so they either “normal” or have the disorder.

Questions Why is it that men are more likely to inherit sex-linked traits like colorblindness and baldness?

Questions Why is it that men are more likely to inherit sex-linked traits like colorblindness and baldness? AGAIN… Men only have ONE X chromosome, so they either inherit the “normal” allele on their X chromosome, or they inherit the recessive allele for the disorder.

Questions Which parent do men inherit sex-linked traits from? _________________

Questions Which parent do men inherit sex-linked traits from? Their mothers…because they get their Y from their dad.

Hemophilia Caused by a recessive allele on the X chromosome, X h Causes excessive bleeding even after minor injury due to lack of clotting factors in the blood. Treatment requires injecting clotting factors