By Amendeep Thakur

When it comes to the genetic history of African-Americans, two incidents played a major role in shaping the genetic component of Black descendants of slaves. The first one was the human trade that led thousands of African slaves to the southern United States, and the second was the Great Migration period, which started around 1910, when millions of African-Americans entered New York, Chicago, and various other parts of America.

In a recent study published in PLOS Genetics, Dr. Simon Gravel and his team researched the DNA of 3726 African-Americans. Among these African-Americans, 82.1 percent have African ancestors, 16.7 percent have European genes, and 1.2 percent show traces of American DNA.

They also claimed that the African-American-mixed genes came into existence around the year 1600, and that the genes that occurred in long stretches in early years now occur in very small chunks. However, as the DNA with European ancestors has longer stretches, that means European genes came into contact with African-American in recent decades.

Scientists and geneticists have made attempts to prove various events of Black history through researching the DNA of living African-Americans. Evidence of cruelties expressed towards African slaves through physical punishments in addition to the sexual exploitation of female slaves by white Americans has been discovered through various analyses.

Apart from this, the migration of the following generations of descendants of African slaves also influenced the distribution of mixed African-American genes throughout the country.

The occurrence of various diseases that resulted from these genetic variations has been examined, born during the times of slavery and migration period. The greatest challenges that the geneticists faced in finding the medical relevance of these diseases were that most of the African slaves in those times were captured from different genetic backgrounds, some of whom already had European or American ancestors.

This DNA research was mainly based on the study of X chromosome (women), as African slave women produced children with their white owners.

The research also targeted on the present location of their subjects to help understand the route of movement made by African Americans, in addition to finding the connection between their genes and the present population of those areas.

Along with Dr. Gravel, many other geneticists such as Dr. Burchard of U.C.-San Francisco; Alondra Nelson, the dean of social science at Columbia University; and Eimear E. Kenny, a geneticist at the Icahn School of Medicine at Mount Sinai in New York, have researched the reasons behind these African American genetic mixtures, their effects on Black Americans of today, and the diseases that may have occurred due to these genes.

Through such research, investigators aim to find solutions and treatments for the diseases that appear to be linked to common traits among the DNA of African-American people.

Source: http://www.nytimes.com/2016/05/28/science/african-american-dna.html?emc=eta1&_r=1