1. Eduardo has a very rare disorder that is caused by a mutation in an imprinted gene that is only expressed from the maternally inherited allele. Is it surprising that Eduardo is a male/XY? No! This is a common misconception. Males and females are equally likely to suffer from imprinting-­‐related disorders, since both males and females only express one allele (in this case, the one that they inherited from their mothers). What matters is not the sex of the child but the sex of parent from whom they inherited the allele. 2. Eduardo’s mother does not have the disorder. Is this surprising? If you didn’t know, what would you say is the chance that she has the disorder? No! Even though Eduardo inherited the mutant allele from his mother we do not know if she was expressing it, because we don’t know which parent she inherited it from. If she inherited the mutant allele from her mother, we expect that she will have the disorder. However, if she inherited the mutant allele from her father, we expect she will not have the disorder. Without any further knowledge, it’s a 50% chance that she has the disorder. 3. Given that Eduardo’s mother does not have the disorder, which of her parents (mom or dad) must she have inherited the mutant allele from? Her father. … So, is her father affected? … Maybe! (see the answer to #2) 4. Celine has a rare disorder that is caused by a mutation in an imprinted gene that is only expressed from the paternally inherited allele. Her parents are not related. Celine maternal grandmother also has the disorder. Is this surprising? Why? Yes! She inherited her mutant allele from her father, who is not related to her maternal grandmother, so this means both her father and maternal grandmother must independently have inherited rare mutant alleles. 5. Kabir has a rare disorder that is caused by a mutation in an imprinted gene that is only expressed from the maternally inherited allele. His maternal grandfather (his mother’s father) also has the disorder. Which parent did this grandfather inherit his mutant allele from? His mother, because, just like all of us, the grandfather only expresses the allele he inherited from his mother. 6. Do we expect Kabir’s mother to have the disorder? Why? The allele is rare, so we assume that the two individuals in the family share the same allele due to inheritance. This means that Kabir inherited his allele from his mom and she inherited it from her dad. So, she has a mutant allele that she inherited from her dad. Because we do not express the allele we inherit from our fathers, we expect Kabir’s mother will not have the disorder.