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Genetics of Populations as Related to Health and Disease

Specific diseases and health issues can be directly connected to the genetics of populations. The distribution of genetic variations differ greatly among human populations. This is largely due to their historical patterns of mutation, migration, reproduction, mating, selection, and genetic drift. Inherited mutations usually occur during gametogenesis within a single individual and eventually passed onto offspring for many generations.

Some mutations that are passed on and become a prevalent polymorphism. These mutations within a population are more frequent than others. This is determined by both evolutionary forces and chance events. For instance, it depends on whether the child who inherited the mutation survives to adulthood, if they reproduce, and whether that child’s children survive to reproduce. 

Additionally, the number of children in a family also influences the likelihood of the mutation to be inherited. This is typically dependent on environmental factors that impact fertility and mating patterns which influence the speed with which a private mutation becomes a public polymorphism. There are well-known examples of what are known as founder mutations in which this trajectory can be documented.

Genetics Mutations of Populations

One example of these genetic mutations of populations can be found in a particular district in what is now known as Quebec (Canada) today. The area was originally founded by only a few families from a particular French province. One of the founding fathers carried a 10kb deletion in his LDL receptor (LDL-R) gene. This mutation was passed down through the generations quickly and today is carried by 1 in 154 French Canadians in northeastern Quebec.

This genetic mutation can now be associated with familial hypercholesterolemia. French Canadians are some of the most susceptible to the disease in the world because of the small founding populations followed by population expansion.

There are also several other examples of genetic mutations that have arisen from an individual and have become more prevalent due to the selective advantage they impart on their carriers. 

 

One of the most well known examples of this type of mutation is associated with sickle cell anemia. The geographical pattern of this mutation strongly mirrors the geographical pattern of malarial infection. It has been molecularly demonstrated that individuals carrying the sickle cell mutation have a resistance to malaria related infections.

However, since there are many of the selection pressures that may have given rise to the current distribution of mutations in particular populations in our evolutionary past, it is difficult to confirm how much variation within or among populations is due to these types of selection forces.

Migration and Genetics Variation of Populations

Another major factor in identifying the distribution of genetic variations within particular human populations is their history of migration and reproductive isolation. According to historical studies and our best knowledge, one of the most important periods in human evolution occurred approximately 100,000 years ago. During this time, humans migrated to other continents from the African basin and established new communities with relative reproductive isolation. 

Therefore, genetic differences among people in different geographical areas have been associated with the concept of race for hundreds of years. While race is still used as a label, the original concept of race as genetically distinct subspecies of humans has been rejected through modern genetic information. For this reason,  it is more appropriate to reconceptualize the old genetics of race into a more accurate genetics of ancestry.

In addition to distant evolutionary patterns of migration, more modern migration patterns also have had a strong effect on the genetics of populations today. For instance, the current population of the United States and much of North America has become extremely genetically diverse. This can be attributed to the mixing of many people from many different countries and continents.

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