Genetics leaves no bones unturned

In their article, Gill and colleagues report their use of molecular genetic techniques to confirm that a group of human remains uncovered in Russia in 1991 include those of the last Tsar his wife and three of their children. The methodology for family lineage identification is based on the fact that mitochondria are maternally derived and their genome contains highly variable segments suitable for DNA sequence analysis. As many copies of the mitochondrial genome exist within human cells the probability of finding intact copies in historic tissue is greatly improved. The family relationship is established by the examination of the inheritance of short tandem repeat (STR) sequences in the human genome. STR sequences, also known as microsatellites, are intermediately variable loci scattered richly throughout mammalian genomes, and contain a short nucleotide sequence ( similar to 2-5 nucleotides long) which is randomly repeated to a limited extent, say between 5 and 20 times. The short DNA sequences containing an STR is ideal for gene amplification analysis with each different repeat type (allele) distinguished by one repeat length difference using the latest gene analysis equipment.