This is the blog for GW students taking Human Evolutionary Genetics. This site is for posting interesting tidbits on: the patterns and processes of human genetic variation;human origins and migration; molecular adaptations to environment, lifestyle and disease; ancient and forensic DNA analyses; and genealogical reconstructions.

GWHEG figure

GWHEG figure

Tuesday, December 4, 2018

Epigenetics found in Single-Cell Archaea, not just Eukaryotes

By; Maria Groussis

In a study by the University of Nebraska-Lincoln, epigenetics was found in single-celled archaea, meaning that they are not only present in eukaryotes as previously thought. Evidence of epigenetics was found in Sulfolobus solfataricus, a sulfur-eating species that live in the boiling, acidic springs of Yellowstone National Park. Through previous studies where they increased levels of acidity through the years, scientist developed three independent and genetically different strains. These super acid-resistant derived strains were named Crenarchaeota (SARC) and they showed a resistance 178 times greater than that of their Yellowstone ancestors. This heritable acid-resistance trait was believed to be resulted from a mutation, but this later was proven to be a false assumption. By sequencing the genomes of the three strains of SARC (SARC-C, SARC-O, and SARC-I) and comparing it to the parental genome the mutations were found. SARC-C had 5 mutations and SARC-O had 29, while SARC-I had none. This implies SARC-I must have a different non-mutation mechanism. The scientists then disrupted proteins that are thought to control the expression of resistant-relevant genes and left no change in the DNA. This immediately stopped the resistance in future generations. Therefore, it can be concluded that SARC-I has an epigenetic-like mechanism.

This new evidence of Archaea having epigenetics indicates that it is not as relatively ‘new’ thing to the Earth. It also raises the question whether the shared common ancestor of Archaea and Eukaryotes had this mechanism, or did each evolve epigenetics independently through coevolution. This also raises the question if epigenetics is the reason why no known archaea cause disease or are antibiotic like bacteria. This finding could accelerate the study of epigenetics in Humans. The differentiation of eukaryotic cells and the occurrences of cancer makes it difficult to study in eukaryotes, but the simplicity of archaea and the structural similarity to eukaryotes make it easier to study. Using archaea to study epigenetics is also faster and cheaper. This may finally help scientists determine how to reverse epigenetics and learn how to switch it on and off.

Monday, December 3, 2018

According to an article titled "Coffee or Tea? The Answer Might Be In Your Genes" written by Nicola Davis, a genetic predisposition to perceiving the bitterness of particular substances is key in our selection of beverages. This study involves two sets of data. The first study shows that particular genetic variants are linked to the strength of perception of different tastes: one specific variant was associated with slightly higher ratings of bitterness for caffeine and another to great bitterness for quinine and a third to greater bitterness for a drug known as propylthiouracil, or prop. The team found people with a greater genetic predisposition to perceiving the bitterness of caffeine drank a little more coffee but an increase perception of the bitterness of quinine and prop were linked to a small reduction in coffee drinking. The team also found that greater perception of the bitterness of prop was linked to a lower chance of being a heavy drinker of alcohol. Their findings also lead to the conclusion that people who prefer to drink tea, drink it as it contains a lower concentration of bitter substances meaning that it might prove more acceptable than coffee to those with a heightened perception of bitterness. It has also been reported that the preference towards tea can be seen as a consequence of abstaining from coffee because our genes might have made coffee a little bitter for our palates to handle.

Nana Evison