Genetics Video http www youtube comwatch v54 wx

Genetics Video! • http: //www. youtube. com/watch? v=54 wx. J 6 E_2 K 8

Sex-linked Traits and Determining Probability with Punnett Squares

Sex Linked Traits • • Humans have 23 pairs of chromosomes One of your 23 pairs are your sex genes o o • • Females: have 2 X chromosomes Males: have 1 X and 1 Y chromosome These chromosomes do more than determine sex-they also carry other genes Example-2 important genes that help control blood clotting are on the X chromosome o A recessive allele for one these produces hemophilia

Determining Probability with Punnett Squares • How to make a Punnett Square: 1 -Draw Box o 2 -Put Mom's Genotype on top, and dad's along side o 3 -Determine the 4 possible offspring by seeing which allele Mom/Dad donates o

Predicting Outcomes • • For Autosomal traits, you will all be heterozygous. o What can predict about the outcomes? For Sex-linked traits (hemophilia) the Mothers will be heterozygous and the fathers will be Normal (dominant) o What can we predict about the outcomes?

How many children total did you make? How Many Boys/Girls ? How many children with blue eyes? How many children with brown eyes? Brown Hair? Blonde hair? How many boys with hemophilia ? How many girls with hemophilia ?

Follow Up Questions 1. None of the males in today's activity were hemophiliacs. Is it possible, therefore, for any of the female children to be hemophiliacs? 2. Why is it much less likely for females to have hemophilia? 3. Do our results match predicted outcomes? 4. What if the Mother was homozygous recessive. How would that change our predicted outcomes?