A) Yes, Jan should undergo genetic sequencing.
BRCA1/BRCA2 are the causes of 20-25% of all hereditary breast cancers, so if Jan's mother and sister both have breast cancer, then the odds are that she has BRCA1 as well.
B)
Pros: If she does have an abnormal BRCA1 gene, she can take steps to lower her risk of breast cancer.
Cons: The tests can incite discrimination towards her in the workplace, and having it known she has a risk for breast cancer can severely increase the cost of insurance.
C) Genetic sequencing could affect the frequency of genetic diseases because the test could point out --- I can't finish because I have to go. I'm so sorry, reask the url of this question and ask someone to finish. Have a nice day!
Vitamins help them function as fats.