Evolutionary Analysis of Colon Cancer

1. What is the estimate of h squared?

Many different sources, including the Encyclopedia of Health and Behavior, the heritability of colon cancer is about 35%.

2. How much influence does selection have on this trait?

A tumor cell population will continue to evolve as a result of the mechanisms of natural selection. As an example, when chemotherapy is used, the resistant tumor cells are being selected for. Three very important conditions necessary for natural selection are obvious in the progression of cancer:
1. First and foremost, there must be variation in the population. Tumor cells are a blend of diverse genetic mutations.
2. Secondly, heritability of the variation must be at work in the population. When tumor cells divide, their daughter cells contain the same genetic mutations as the parent cells.
3. Finally, variation has to affect fitness.
a. High fitness is easily achieved fore tumor cells since they are capable of growing and dviding beyond normal, healthy growth potential.
b. These tumor cells no longer need outside signals to divide.
c. With the ability to suppress the internal mechanisms for self-destruction when genetic mutations have overcome the cell, they are capable of proliferation.
Science Daily: Does Natural Selection Drive the Evolution of Cancer
http://www.sciencedaily.com/releases/2006/11/061117114616.htm

3. What effect would inbreeding have on this trait (cancer)?

Any time there is inbreeding in a population, the frequency of recessive phenotypes, sometimes deleterious phenotypes, increase. For this reason, inbreeding in a population with genetically caused colon cancer would increase the frequency of colon cancer seen in this population.