And here is its answer key: http://www.biologycorner.com/worksheets/genetics_practice_key.html
try some sex linkage questions here: http://www.k-state.edu/biology/pob/genetics/intro.htm
SEX LINKED GENES
The sex chromosomes are XX and XY in humans. Some alleles are located on the X chromosome. But very few on the Y chromosome. Remember that females have the genotype XX and males have XY.
The Y chromosome carries very little information, only enough to influence the embryo on the path towards male primary and secondary characteristics.
Meanwhile, many RECESSIVE ALLELES are located on the X chromosome, including
1. hemophilia, the inability to clot blood
2. colourblindness inability to tell the difference between red and green colour
3. baldness
These characteristics are far more common in men than women because men have only one X. And if that X contains the recessive allele, they will show the phenotype. Meanwhile, women may have the recessive and their "normal" dominant X will protect them. For example
An example of using a punnet square to calculate probability is here:
Some things to note about sex linkage: Signs of sex linked alleles are:
1. more males get the phenotype, but women can be carriers
2. men can inherit from mother but not father (because men get their X from mom)
3. Women have an extra X and this protects them. Women must be homozygous to show the sex linked phenotype.
Further reading on sex linkage here http://learn.genetics.utah.edu/content/pigeons/sexlinkage/
FYI if you are a guy and you want to know if you're colourblind: Test yourself here: Apparently most men find out they are colourblind from their science teacher...
http://colorvisiontesting.com/home.html
