Darwin's evolutionary theory in question?

A recent field called epigenetics, is based on studying the inheritance of characteristics not found in an organism's DNA sequence. Scientists in this field, argue that environmental factors, such as diet, temperature, and exposure to certain substances, can create distinct phenotypes without directly changing gene structure. These newly acquired phenotypical characteristics, then are passed on to a second generation.

This somewhat contradicts Darwin's theory which states that evolution is a result of a population and not of a single individual. Some scientists though, view results of epigentic research as an add on to Darwin's evolutionary theory, saying that both purely genetic characteristics as well as ones caused by environmental factors in single individuals are responsible for evolution.

Results of various studies, such as those done with Drosphila melanogaster and Agouti mice back up this new field. In the Drosphila experiment, a certain white eyed only strand was chosen. Embryos which are naturally nurtured at 25 degrees Celsius were nurtured at 37 degrees Celsius, resulting in red eyed offspring. After crossing these red eyed flies, the offspring appear partly red eyed without further temperature alterations, even though these flie's genes only encode for white eyes. Agouti mice are yellow, fat and prone to diabetes. When fed a diet high in B12 vitamin, follic acid and cholin prior to and during pregnancy, the offspring appear brown, slim and healthy.

Important factors that can account for this type of inheritance, are the action of histone protiens and cell memory. Histones, which are proteins important in the packaging of DNA, can activate or deactivate genes, at sites referred to as epigentic markers, depending on whether they are acetylated or methylated. It may be that certain environmental factors, can influence this step.

Ongoing research is aimed at explaining how these epigenetic markers are selected and the mechanism through which they are preserved and passed on to a second generation. During cell divison , histones break apart from the DNA strand. Because of this, it is not clearly known how the same gene can be silenced, or altered, in the daughter cells as well.

-Julio Rodriguez (Group C)

Update: Methylation of certain histones is catalyzed by a family of proteins called histone methyltransferases, or HMTs. Ifound a study that said "5'-S-(propionic acid)5'-deoxy-9-(1'-β-D-ribofuranosyl)1,3-dideazaadenine was an activator of EcoP15I and HhaI DNA methyltransferases." I believe this to be an amino acid derivative which can bind and activate a certain complex responsible for inducing transcription and consequently the synthesis of HMTs. I could not find what environmental factors were responsible for this.