* The gene is NOT on a sex chromosome, but SEX affects the phenotype * Example-baldness- dominant in males, recessive in women * If ‘B’ represents bald and ‘b’ is hairy then Men must be bb to keep hair Women can be Bb or bb to keep hair

* Caused by a gene that is located on a SEX chromosome (X or Y) * Most sex-linked traits are found on the X chromosome * Is the pedigree beside this like MOST sex- linked traits?

* Most are recessive * Examples-hemophilia, red-green colorblindness * Males are more likely to have these because they cannot be carriers * Why? * Males are XY-if their ‘X’ has a bad gene, there is nothing on the ‘Y’ to dominate over it

*Nn*Nn * X N X N =Normal * X N X n =CARRIER, but IS NOT colorblind * X N Y=Normal * X n Y=HAS red-green colorblindess

* Carrier mom X N X n * Normal Dad X N Y X N X n X N X N X N X N X n Y X N Y X n Y

* Orange and Black Alleles are on the X chromosome in cats * White is on another chromosome (autosome). * Result-some cells make black fur, some orange

* Polygenic-more than one pair of alleles determines phenotype--eye color

* Female genotype? * Male genotype? * What percent of possible offspring are female? * What percent of possible offspring are male?

What is the genotype of a woman who is a carrier of hemophilia? What is the genotype of a man who does not have hemophilia? Will any of their children potentially have hemophilia? What sex will the child have to be?

Last vocabulary term of importance. Purebred – Always breeds true to dominant trait. i.e. homozygous dominant individual