DNA Favoritism Leads to the Continuation of Diseases

     There are many diseases that are passed down from generation to generation that are extremely harmful to those who are affected, while other disease are beneficial to the population. Some examples include Sickle Cell Anemia, six fingered dwarfism, and other genetic diseases. Typically individuals are supposed to acquire one-half of their genes from their mother and one-half from their father, but a recent study shows that this may not be the case.

Sickle Cell Anemia can be beneficial to those living in places with high rates of Malaria, giving the bacteria that cause Malaria a less livable environment than normal red blood cells. 

      Joseph Lachance and Sarah A. Tishkoff have studied gene conversion during meiosis and have found that certain forms of DNA are biased, potentially explaining why certain diseases are still very common throughout the population. One phenomenon believed to have lead to a small amount of bias is GC-bias, where a DNA mis-match causes one of the alleles from parent to be replaced, possibly by another allele from the same parent. This would result in the offspring having two alleles from the same parent instead of one allele from each.
 
       In order to see if this bias is the reason that so many diseases are persistent in their appearance in the population, Lachance and Tishkoff analyzed the genetic sequence of twenty-five individuals from five very diverse populations. Of the many polynucleotide sequences found, they grouped the mutations involving a single nucleotide into groups according to the type of change that occurred (either G and C to A and T, or the reverse). They discovered that GC-bias did play a role in deciding which genes underwent changes, but they also found that in areas where recombination occurred, were very popular spots for gene conversion.

      Although, the strength of their results was not incredibly strong, the results to do show that GC-bias is responsible for certain diseases still existing among certain populations. They also found that the reason GC-bias keeps diseases around is because often when the genes are converted, they are given another of the same allele, making the individual homozygous. If this allele is the recessive allele, and the disease is homozygous recessive, then the offspring will be affected with the disease and the chance of it being passed on becomes greater. If the GC-bias is occurring often, as Lachance and Tishkoff have shown, then if the conversions are equipping offspring with the genes for a disease, there is more of a chance that the disease will stay common in a population.

Orginal Article: DNA bias may keep some diseases in circulation, biologists show