The Drosophila melanogaster Genetic Reference Panel
Mackay, Richards et al., Nature
North Carolina State University's Trudy Mackay and her colleagues present the Drosophila melanogaster Genetic Reference Panel, "a community resource for analysis of population genomics and quantitative traits."
The Surprising Variability of Mitochondrial DNA
March 09, 2010
Researchers led by Johns Hopkins' Nickolas Papadopoulos found that different versions of the mitochondrial genome can be found in different organs in the same person. As they report in Nature, the researchers used next-gen DNA sequencing, and were able to find single-letter DNA changes that occur in as few as one in 10,000 mitochondria. And when the researchers tried to see if the variations were limited to cancer cells, what they found is that the mitochondrial DNA in healthy colon tissue can also vary. The implications for forensic science are clear — if mitochondrial DNA taken from a crime scene doesn't match a DNA sample taken from a suspect, that doesn't necessarily mean that the two samples aren't from the same person. And as for cancer detection, the researchers say that mutations specific to colon tumors can be found in tiny blood samples, and that those mutation signatures vanish after the tumor is removed.
The concept that
The concept that mitochondrial DNA may vary slightly in nucleotide sequence is hardly that surprising at all. Mitochondria DNA is maternally derived, originally from the oocyte. The oocyte is one of the largest cells in the human body. The average liver cell is known to feature about 1700 mitochondria on average, so an oocyte probably features several times this number. While half of the DNA and centrioles in a fertilized egg are derived from the male, all of the mitochondria and its DNA is from the female. During the reductive cell divisions following fertilization, the populations of mitochondria become portioned out in the daughter cells, which ultimately give rise to different organs following differentiation. It is reasonable to suppose that mitochondria undergo faster rates of replication than the cells that harbor them, so there would be more opportunity for SNP's within mitochondrial DNA to accumulate and be propagated, even within the same individual. Mitochondrial genes may represent the ultimate "selfish" genes from the Richard Dawkin's perspective.