Final answer:
Dr. Aikenhed may be concerned about Leah and Luke potentially carrying the BRCA gene mutations and being at higher risk for developing cancer in the future.
Step-by-step explanation:
According to the provided information, the specific gene listed as being defective in the genetic disorder is not mentioned. However, the question asks about the concerns of Dr. Aikenhed regarding Leah and Luke, despite them not having cancer. The gene mentioned in the previous information, BRCA1 and BRCA2, is highly prevalent in Ashkenazi Jews and greatly increases the risk of cancer. Therefore, Dr. Aikenhed may be concerned about Leah and Luke potentially carrying the BRCA gene mutations and being at higher risk for developing cancer in the future.