A CLINICAL GENETICIST IS STUDYING A FAMILY WITH A RARE HEART DISEASE. THE GENETICIST DISCOVERS A MUTATION THAT HE BELIEVES MAY BE THE CAUSE OF THE DISEASE.
HOWEVER, THE MUTATION IS IN A GENE CALLED MRAG1 THAT IS NOT EXPRESSED IN THE HEART. THE GENETICIST ALSO PERFORMS AN EXPRESSION MICROARRAY EXPERIMENT WITH A BIOPSIES OF HEART TISSUE OF AFFECTED AND UNAFFECTED FAMILY MEMBERS AND DISCOVERS THAT A GENE CALLED HET1 IS EXPRESSED AT MUCH LOWER LEVELS IN FAMILY MEMBERS WITH THE DISEASE COMPARED TO MEMBERS WHO DO NOT HAVE THE DISEASE. IN OTHER WORDS, INDIVIDUALS WHO HAVE THE MRAG1 MUTATION HAVE LOW EXPRESSION OF HET1. THE MRAG1 GENE IS DISCOVERED TO BE ABOUT 80,000 NUCLEOTIDES AWAY FROM THE HET1 GENE. HOW MIGHT A MUTATION IN MRAG1 LEAD TO LOW EXPRESSION OF HET1? REMEMBER THAT MRAG1 IS NOT EXPRESSED IN HEART.
A clinical geneticist is studying a family with a rare heart disease. The geneticist discovers a mutation that he believes may be the cause of the disease. However, the mutation is in a gene called mrag1 that is not expressed in the heart. The geneticist also performs an expression microarray experiment with a biopsy of heart tissue of affected and unaffected family members and discovers that a gene called het1 is expressed at much lower levels in family members with the disease compared to members who do not have the disease. In other words, individuals who have the mrag1 mutation have low expression of het1. The mrag1 gene is discovered to be about 80,000 nucleotides away from the het1 gene. How might a mutation in a mrag1 lead to the low expression of het1? Remember that mrag1 is not expressed in heart.