Biology Forums - Study Force

Jane Brown has ptosis of the eyes (pronounced toe-sis).  This results in drooping eyelids so that the eyes look half open all the time.  Harry Brown has normal looking eyes.  Ptosis is a rare autosomal dominant condition and Jane is known to have a heterozygous genotype as her mother Mary Smith, has normal eyes.  Jane has 1 younger brother, Max, also with the condition, while Harry has an older sister June.

a)   Use a diagram to set this family pedigree out in a logical manner.  Jane’s parents are Jim and Mary and Jane’s children are Daniel, Mark and Eve (born in that order).  Harry’s parents are Tom and Susie.  Identify all genotypes and phenotypes for the people in this extended family where possible. 

b)   For the children of Jane and Harry determine what eye condition they could have and the probability for each. 

c)   Harry also has A type blood group and is known to have an IA i genotype for this, while Jane has AB blood group.  Copy the table with the eye information from part (b) to here and then add this new information to it so you can determine the phenotype probabilities for any children they may have considering both traits at the same time.


Any help would be greatly appreciated  :)

Jane's father must have the condition since the mother does not.

Jane's children have a 50% chance of having the condition.

Harry's parents do not carry the defect.

For bloodtype, the children can be A, B or AB with the odds being 50% AB, 25% B, and 25% AB.