Two Questions

1) Provide an estimate of h2 for the disorder. Based on this, discuss how much influence selection could have on this trait.
Most forms of OI are inherited dominantly meaning only one copy of the mutant gene is required for the expression of OI. Type I, the mild form of OI, is the most common disorder (about 4-5 people out of 100,000 people are affected). In type I OI, the mutation produces normal collagen and mutant collagen because the normal allele (from a normal parent) produces normal collagen and the mutant allele (from an OI parent) produces mutant collagen. Consequently, normal collagen combined with mutant collagen produces a mild form of OI. The most severe form of OI is type II in which only mutant collagen is produced; as a result, bones that are made become brittle. h² shows the amount of genetic variation that is due to additive effect. Since OI is a genetic disorder, h² should be high. The equation, R=h²S, shows that selection has a strong influence on this trait because the mutation reduces the fitness of the person with this disorder.

2) What effect might inbreeding have on this disorder?

Inbreeding increases homozygosity and decreases heterozygosity. Therefore, inbreeding will result in individuals with severe OI (Type II) or no OI (normal) and no mild forms of OI (Type I). The frequency of OI (Type II) in the population will increase and Type I (heterozygous genotype) will decrease.

http://ghr.nlm.nih.gov/condition=osteogenesisimperfecta

John's Response

I learned that there were different forms of OI and that the different types ranging in different levels of severity. Through evolution, it is amasing how there is such a great similarity between the chicken and human. And, a possibility for the their differences is a divergence from a common ancestor. Gene targeting can be a difficult process and it is impressive how gene therapy could target the defective genes with a hope to help the OI patient.

Dung's Response

Most mutations at the COL1A1 and COL1A2 results in Type I or Type IV which usually follows an autosomal dominant pedigree. This means that they can receive the allele from either parents. Mutations in CRTAP and LEPRE1 results in Type III and usually follows an autosomal recessive pedigree. This means that offsprings must receive the recessive allele from both parents.

I learned that OI has some medical advancements in improving the lives of patients with OI because we cannot control what genes are passed on from parent to offspring. Thus, we must help those that receive slightly deleterious or deleterious genes. This will enable OI patients to have equal chances of reproduction as the rest of normal people without the mutated genes.

Why does a doctor need to know evolution?
Doctors should be well aware of evolution because each individual is different from another. Since people tend to ask doctor's about their decision, doctors should be well versed in all aspects of biology and evolution is included. For example, a person that has a regular cold. The person asks the doctor if he can get antibiotics. What should the doctor say? Should he state that it is a regular cold and the immune system can easily handle it or should he prescribe him antibiotics which may mutate the bacteria and then become resistant to bacteria? As one can see, using antibiotics increases the likelihood of bacteria to becoming resistant to the drug because some bacterium cells survive and then reproduce which causes all of their offspring to have the antibiotic resistance. Therefore, it is imperative for doctors to know evolution as well because this will play a role in making decision when a patient asks for drugs for their problems.