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*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
*N
n
* XNXN=Normal *XNXn=CARRIER, but IS
NOT colorblind
*XNY=Normal
*XnY=HAS red-green colorblindess
*Carrier mom XNXn
*Normal Dad XNY
XN Xn
XN XNXN XNXn
Y XNY XnY
*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