Genetics Review

Question 1

What is the testing approach for CF?

Answer 1

begin with targeted screening with a MINIMUM 23 mutation panel (expanded panels are available) then follow up with scanning if the targeted is negative (applicable only for individuals with a positive family history or high risk, obligate carriers)

targeted scanning is sufficient for the general population. In other words, if there is no reason to suspect CF, and the mutation panel is negative, scanning testing is not necessary

Question 2

Does a screening test include introns?

Answer 2

Not commonly (but can), just exons, promoter regions, and relevant regions in introns that have seen mutation before. Never going to be 100% accurate but gets close (98-99%)

Question 3

Are all nonsense mutations pathogenic?

Answer 3

Yes. all frameshift mutations will eventually cause truncating sequences. Missions mutations on the other hand can be hard to interpret. If you see a missense mutation that has never been seen before and a person has a disease, you CANNOT assume that the missions mutation is the direct cause of the disease

Question 4

Can normal alleles ever expand?

Answer 4

NO, they are stable. A mutation must arise in order for TNR expansion to occur

Question 5

What protein would indicated possible DMD or BMD?

Answer 5

serum creatine kinase would be elevated (indicates muscle weakness)

Question 6

What is the preferred testing strategy for DMD?

Answer 6

scan the DMD gene for large deletions. A targeted approach is not useful because there are no common deletions for DMD> The only commonality is that large deletions are the cause in the majority of cases

Question 7

What is the difference between gain of function and loss of function mutations?

Answer 7

gain of function means that the protein is made and acts in some unintended manner, while loss of function mutations causes the protein never to be made