Friday, September 28, 2007

Mammoth DNA

Whole-Genome Shotgun Sequencing of Mitochondria from Ancient Hair Shafts. 2007. M. Thomas P. Gilbert, et al. Science 317: 1927-1930.

Art by Roy Krenkel from Tanar of Pellucidar
Abstract: Although the application of sequencing-by-synthesis techniques to DNA extracted from bones has revolutionized the study of ancient DNA, it has been plagued by large fractions of contaminating environmental DNA. The genetic analyses of hair shafts could be a solution: We present 10 previously unexamined Siberian mammoth (Mammuthus primigenius) mitochondrial genomes, sequenced with up to 48-fold coverage. The observed levels of damage-derived sequencing errors were lower than those observed in previously published frozen bone samples, even though one of the specimens was >50,000 14C years old and another had been stored for 200 years at room temperature. The method therefore sets the stage for molecular-genetic analysis of museum collections.

From the press release:

A new DNA-method to examine hair will give us more precise information about why the mammoth died out, or what the ingredients are in the cocktail of human races that are mixed in Europe and elsewhere.

“So far you would have to drill in old bones if you wanted to compare the genetic imprint of mammoths to that of elephants, or if you wanted to see how they coped during the ice-age before they died out. Usually, the problem is that the remaining DNA samples have been scarce, and that they have been “polluted” by bacteria. But DNA from hair is very clean because it has been encapsulated in keratin, a kind of plastic membrane that protects the hair and the DNA” says Thomas Gilbert.

The centre of research has been the mitochondria. A mitochondrion is a kind of power plant in the cell, and it is very suitable for use in comparable DNA-studies of both mammals and humans.