What is the mode of inheritance for breast cancer? Explain.

Question:

What is the mode of inheritance for breast cancer? Explain.

Breast Cancer

Breast cancer is the abnormal growth of cells throughout breast tissue. This includes certain anatomic points of the breast including ducts, lobules, nipples, etc. Breast cancer presents various ways and at the time, can be difficult to diagnose and treat properly.

Answer and Explanation:

There are many different genes associated with breast cancer. The most well known and studied are BRCA1 and BRCA2 which are inherited in an autosomal dominant fashion. There are other genes associated with breast cancer as well, but they are not as heavily studied and can easily turn a simple answer into a 10-page paper. Other genes associated with breast cancer are ATM, STK11, CDH1 and many others and can increase chances for developing breast cancer as well. BRCA1 and BRCA2 are single-gene mutations, meaning that only a single gene is affected. The most prominent cause of familial breast cancer are BRCA1 and BRCA1 mutations.

Breast cancer caused by BRCA1/2 mutations is inherited in a dominant pattern would mean only one parent would have to have the mutated gene for the offspring to inherit it. Men and women can both have this mutation. So if a mother has a BRCA1 or BRCA2 mutation and a father did not, their offspring have at least a 50% chance of expressing this as well which would increase the chances of developing breast cancer, as well as ovarian cancer. The only way to know if one expresses this because it is not observable by the naked eye, would be to get tested for it. So let's say we know the mother has this trait, which we will identify as "B" and the recessive variant we will express as "b". So the mother genotype can either be BB or Bb, but just for the example we will say "Bb". The father does not express this at all so his genotype will be "bb".

B b
b Bb bb
b Bb bb

Breast cancer can also present due to several environmental factors. Not only this but it also can arise from other gene mutations. As mentioned earlier, they are not as heavily studied because they account for very few cases. The limited cases hinder researchers in gathering deeper knowledge of the mode of inheritance.


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Pedigree Analysis in Human Genetics: Inheritance Patterns

from Biology 102: Basic Genetics

Chapter 6 / Lesson 3
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