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Cuba: A Country With Little Genetic Drift
Certain genetic disorders tend to be more prevalent in specific countries or regions of the world than in others. This is particularly true in countries and regions that experience little to no immigration or emigration due to the concept know as "genetic drift" (for an explanation of the effect of genetic drift, or lack thereof, on the incidence of a genetic disorder in a defined population, please see this article).
One such country is Cuba, which forbids its citizens from leaving the country and allows few foreign visitors. The following sections describe the commonly seen genetic abnormalities in Cuban people.
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Genetic Disorders Seen In Cuba
The most common genetic disorder in the Cuban population is sickle-cell anemia, as an estimated 3.7 percent of all Cubans carry one of the mutations that are causative of this dreaded blood cell disease. This is not particularly surprising, however, because the incidence of sickle-cell anemia is abnormally high among people of African descent and a large portion of Cuba's population originally descends from Africa.
Another genetic condition that has struck many Cubans is phenylketonuria, which is a metabolic disorder that causes those who have it to suffer from mental retardation, seizures, and brain damage. An estimated 1 in every 50,000 Cuban babies have phenylketonuria, which is higher than the world-wide incidence for this severe disorder.
Congenital hypothyroidism is another genetic condition that is relatively common among Cubans as a whopping 1 in about 4,000 Cuban babies are born with this disorder. Those who have congenital hypothyroidism chronically experience several or all of the following symptoms: fatigue, excessive weight gain, headaches and depression, among many others.
Down Syndrome, which is a genetic disorder that is due to abnormal chromosome count and not mutation and is not inherited because Down individuals are infertile, is also relatively common in Cuba. An estimated 6.8 of every 10,000 Cuban children under age 5 are inflicted with this disorder. Characteristics of Down Syndrome include cranio-facial defects, severe mental retardation, and poor muscle tone, among several others.
Finally, on a positive note, Cubans experience a relatively low rate of mental retardation due to genetic causes not related to Down Syndrome. Whereas it has been estimate that about 2-3 percent of all babies born in developed countries suffers from congenital mental retardation, only about 1 percent of Cubans experience this fate.
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Cuba's National Genetics Program
You may be interested to learn that in 2003, Cuba set up a national genetics program that is now staffed with over 1,600 individuals who work at more than 180 centers nationwide. This program is specifically aimed at researching and developing effective treatments for genetic disorders, pre-screening fetuses for genetic abnormalities, counseling parents on the subject of genetics and caring for those who have a genetic condition. For example, as part of the program, all women of Cuba are able to have their developing fetus tested for sickle-cell anemia, phenylketonuria, and neural tube defects, among many other genetic disorders. Additionally, pregnant women of age 37 or older are offered the opportunity to have their fetus tested for Down Syndrome and other chromosomal anomalies.
As another example, to facilitate the care of people who have genetic abnormalities, Cuba's genetics program has generated a large registry that is populated with the names and contact information of 360,000 such individuals. Specifically, the program helps manage the care of these individuals through collaboration with community social workers, who routinely monitor sick individuals' health status and living conditions.
Finally, to best advance genetic research for the purpose of discovering optimal treatment methods for genetic conditions, Cuba's genetics program has made it a top priority to train young scientific investigators. To this end, the program has implemented a strenuous Human Genetics course in all of Cuba's medical schools. Further, more than 50 research projects are now being conducted in laboratories throughout Cuba, which represents a great increase over the number that existed before the program was initiated. A national registry of over 43,000 families who have multiple members who suffer from the same genetic condition also has been created to facilitate the discovery of new mutations that are causative of disorders such as asthma, high blood pressure, diabetes, heart disease, cancer, alcoholism, mental retardation, and psychological conditions, including depression, bipolar disorder, and schizophrenia, for example.
Read here to learn more about this excellent program.
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A.L. Cruz et al., Epidemiology of Prenatal Genetic and Environmental Factors of Mental Retardation in Cuba, MEDICC Review, 2008: http://www.medicc.org/mediccreview/articles/mr_48.pdf
A.L. Cruz et al., Medical genetic services in Cuba, Rev. Cubana Genet. Comunit., 2007: http://bvs.sld.cu/revistas/rcgc/v1n1/gco02107.pdf
MEDICC Review, Cuba's National Medical Genetics Program, International Journal of Cuban Health & Medicine, 2009: http://www.medicc.org/mediccreview/index.php?issue=7&id=71&a=vahtml