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Genetics (Expert Forum)
BRCA-1 Odds
Answered by
AccessDNA
Welcome to the Genetics Forum! Questions in the Genetics Forum are being answered by genetic experts from AccessDNA. This forum is for questions and support regarding a person’s predisposition to a variety of medical conditions such as Ashkenazi Jewish Diseases, Bleeding Disorders, Blood Clotting Disorders, Cancer Genetics and Hereditary Cancer Syndromes, Chromosome Abnormalities, Congenital Birth Defects, Cystic Fibrosis, Family History, Fragile X Syndrome, Infertility, Newborn Screening, Rare Genetic Disorders, Prenatal Screening and Testing.
This forum is for questions and support regarding a person’s predisposition to a variety of medical conditions such as Alzheimer’s Disease, Blood-clotting Disorders, Breast Cancer, Cystic Fibrosis, Diabetes, Marfan Syndrome, Ehlers-Danlos Syndrome, etc.
BRCA-1 Odds
by lonebrother, Aug 10, 2009 06:56PM
We have the BRCA-1 mutation on my dad's side of the family. Three geneticists claim that the odds of inheriting the mutation are 50/50 with no exception. 6 out of 6 of his kids have the mutation. While statistics can jive with these results, it really is quite unlikely. So, something else is going on beyond the 50/50 odds. Can someone explain? Is "overexression" the right term here? If so (or not), how does that work?
Doctor's Answer
by Jordanna Joaquina, MS, CGC, Aug 12, 2009 11:15AM
, Aug 12, 2009 11:15AMTo: lonebrother
Although it may appear that the odds are greater than 50% given the amount of family members with the mutation, it's still 50/50 as the geneticists explained.
Not to minimize the significance of a BRCA mutation, but one way to explain it is like tossing a coin. Each time you flip a coin there is a 50% chance to get heads and a 50% chance to get tails. Each flip is an independent event and the coin is unaware of the last result or the next result. Each pregnancy is an independent event with a 50% chance of inheriting the gene copy with the mutation and a 50% chance of inheriting the normal gene copy - that is as long as only one parent has a mutation and not both parents. Although it is very unfortunate, this is how 6 children can each have had inherited the same mutation from a parent.
As you are probably aware, having a BRCA mutation does not cause cancer but does increase the lifetime risk to develop certain types of cancer. We recommend that your family meet with genetics and oncology to discuss appropriate, routine cancer screening and surveillance (if not already doing so). We hope your family is getting the support it needs and wish you the best.
Not to minimize the significance of a BRCA mutation, but one way to explain it is like tossing a coin. Each time you flip a coin there is a 50% chance to get heads and a 50% chance to get tails. Each flip is an independent event and the coin is unaware of the last result or the next result. Each pregnancy is an independent event with a 50% chance of inheriting the gene copy with the mutation and a 50% chance of inheriting the normal gene copy - that is as long as only one parent has a mutation and not both parents. Although it is very unfortunate, this is how 6 children can each have had inherited the same mutation from a parent.
As you are probably aware, having a BRCA mutation does not cause cancer but does increase the lifetime risk to develop certain types of cancer. We recommend that your family meet with genetics and oncology to discuss appropriate, routine cancer screening and surveillance (if not already doing so). We hope your family is getting the support it needs and wish you the best.
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