1
Q
a colour blind boy has parents who both have normal colour vision. determine the genotype of his parents and produce a genetic cross to illustrate tour answer.
A
see diagram
2
Q
what are three things to look for when looking for evidence of sex linkage?
A
- look for much greater numbers of affected males than females, or no affected females at all (note there have to be lots of offspring to be confident)
- affected mother with a normal son - this cannot happen if the gene is a sex linked recessive one (son would also be affected because he would inherit X with recessive allele from mother and Y from father
- affected daughter with normal father - this cannot happen if the gene is sex linked and recessive (daughter would be normal as she would inherit X with dominant allele from her father)
