Huntington's disease is an inherited disorder that affects the nervous system. It is caused by a dominant allele HHH. The recessive allele hhh results in a normal phenotype (no disorder).
The pedigree chart below shows the inheritance of Huntington's disease in a family:
a.[3]
Give the genotype of Person 2 and explain your answer.
b.[3]
Person 10 and Person 12 are expecting a fourth child. What is the probability of this child having Huntington's disease? Describe the Punnett square to support your answer.
c.[2]
Explain how the pedigree chart shows that the allele for Huntington's disease is not on the Y chromosome.