Odds of Affliction in Paternally Imprinted Pedigree

Subject : Biology

Question:

In a paternally imprinted pedigree, what are the odds that an individual born between an unafflicted father and afflicted mother will be afflicted with condition A?

Expert Verified Answer:

In a paternally imprinted pedigree, genes inherited from the father are imprinted, or “silenced,” meaning they are not expressed. This means that even if the father carries a gene for a particular condition, it will not manifest because the gene from the father is inactive. However, if the mother is afflicted with the condition, her gene will be expressed because maternal genes in this scenario are active.

For a child born to an unafflicted father and an afflicted mother in a paternally imprinted condition, the odds of the child being afflicted depend on whether the condition is dominant or recessive:

• If the condition is dominant, the child has a 50% chance of inheriting the active gene from the mother, and thus will be afflicted.
• If the condition is recessive, both copies of the gene must be defective for the condition to manifest. If the father does not carry a copy of the defective gene, the child will not be afflicted because the child will inherit one normal gene from the father.

The odds of affliction depend on whether condition A is dominant or recessive, but if it’s dominant, there’s a 50% chance that the child will be afflicted.