Cuban genes

¨Progreso Semanal¨ recently published an interview with Dr. Beatriz Marcheco Teruel, a specialist in Clinical Genetics of the National Center of Medical Genetics following her research: Genetic identity of Cuban population, which offers details of who Cubans are in biological terms. It is an interesting look that we wanted to share with the readers of OnCuba.

What were the expectations of the research on the genetic identity of Cuban people?Since the late 90s of last century, genetics researchers developed a new method to locate genes associated with the origin of diseases, this method was called ” miscegenation mapping”. This type of study is particularly applied to populations that have been originated from the mixture of different ethnic groups in the recent past (no more than about 15 generations ago).

Our geographic region provides an ideal setting to study miscegenation present in the DNA, as it has a population in which the mixture of different human groups – Native Americans, Europeans, Asians and Africans-took place in the relatively recent past. This makes possible its present generation to have regions in the genome where genetic information is conserved in a way that the percentage of genes belonging to the group or ethnic groups who originated it, can be estimated in each person.

What interest do these studies have to the social sciences?

They are important to characterize genetic heritage of our nation and contribute from this field to delve into the history of Cuban people. From these results we can draw a path towards our origins and contribute, from genetics, to confirm the findings of researching that other sciences such as history, anthropology, archeology, ethnology, ethnography have previously obtained.

I am convinced that by increasingly knowing about our origins, we can answer the ancestral questions of who we are and where we come from; it helps strengthening our identity as people and our unity as nation.

In your opinion, can we say, as Fernando Ortiz noted, that the word “race” is a bad word? Is it possible to find “scientific” sustenance to an ideology of racial superiority, or to racism?

Marti stated “… there are no races: there are just modifications of man, in the details of habits and ways which do not change identical and essential features of them …”

In the field of genetics and biomedical research the term “race” has been increasingly losing its validity and today, one of the problems with the use of this word as an identifier to classify individuals, is the absence of a clear definition of this term .

Historically, “race” has been classified on the basis of cultural and biological characteristics, including culture, religion, ethnicity, geographic origin, as well as morphology and color of the skin. However, these last two are not considered good indicators for racial description, because they are the result of adaptation to environmental conditions and may be subject to evolutionary changes yet.

The paradigms of human identity based on the concept of “race” as a biological and / or sociocultural construct can be questioned in light of the information available on the genetic variations found in the human genome sequence. Human beings are identical in more than 99% of our genome, the differences between us are on the order of 0.2% to 0.4% and it is only in that small range of variability of genetic information on which the wide diversity of our species lies.

There is a recently published study (1), which compared the responses of individuals who have been totally blind from birth to the question: how do you define the concept of “race”? with the response to the same question asked to sighted people. Both groups were questioned about: what is your definition of “race”? What is your first memory of “race”? If you marry to someone of a “race” different from yours, how would your family react? Why do you think “race” is important for some individuals? The study findings showed that in the opinion of both groups of participants the differences between “racial groups” are determined by characteristics that can be easily seen. Similarly, the results of this study reaffirm how “race” and racial thinking are internalized through of interactive social practices that train people to interpret in a certain way the world around them and these practices are so deeply rooted that even blind people “see” and interpret the definition of “race” based on visual “clues”, in a conceptual mode. These elements suggest that “race” is a socially built concept with a strata system that is non-argued by natural or biological differences.What defines, from the biological point of view, the changes in skin color?

The skin pigmentation is an adaptive and labile trait that has changed more than once in the process of human evolution, and currently has no value in determining phylogenetic relationships of modern humans. The geographical distribution of the skin color of humans is one of the best examples of the effect of natural selection that occurs from a strong relationship between phenotype and environment.

Ultraviolet radiations have highest incidence at the level of the Ecuador and decrease as taking distance from it. The investigations show that the skin color is darker in the southern hemisphere than in the north one, in the equivalent latitude, and it has been explained that these hemispheric differences are caused by higher levels of ultraviolet radiation in the southern hemisphere, due to factors as the concentration of ozone, atmospheric turbidity and the distance from the earth to the sun, among others.

The melanin is a black or blackish brown pigment in granular form and is the primary determinant of human skin color, an addition of biopolymers synthesized in melanocytes located in the basal layer of the epidermis. Although human beings generally possess a similar concentration of melanin in the skin, some ethnic groups and individuals express to a greater extent the effects of this pigment -producing gene and therefore a higher concentration of melanin in skin, hence its darker color.

Recent research aimed with growing evidence that changes in skin color have an adaptive component and are associated with the exposure to ultraviolet radiation as part of the process of natural selection.

How could you make the genetic characterization of Cuban people?

We use a “small scale” sample of our population, depending on the distribution by area of residence, gender, age groups, provinces, municipalities and other variables. We were able to study a little more than 1000 individuals from 137 of the 168 Cuban municipalities, of all the provinces. With the consent of each person we made interviews, anthropometric measurements, measures of the melanin index in order to have a more objective measurement of skin pigmentation and took a blood sample for DNA studies.

What do our genes say? Is it true that, as Guillen immortalized, “we all have of congo and Karabalí”?

The study results confirm not only that we have been mestizo for a long time, but new generations of Cubans are and will increasingly be mestizo.

All individuals studied have, at the same time, genes of European origin (69 %), genes of African origin (19 %) and even more, in the genetic background of our current population, we kept our Amerindian ancestors genetic information (12%). We have of congo and Karabalí, and much more. We are sure that it will become increasingly complex to group Cubans in 3 skin colors “blacks, whites and mestizos” since such classification boundaries become increasingly imprecise.

In terms of genetic studies, w hat new research do you hope to develop in the coming years?

Now we are working in a new stage of research, related to genes that are associated with skin pigmentation in our population. We also aim at studying genetic markers at the level of mitochondrial DNA and Y chromosome, to better understand where our ancestors come from and to study in more detail the genetic information coming particularly from our indigenous ancestors. All this will be useful to characterize in much detail as possible our genetic identity.