Analysing DNA from ancient human remains the researchers can determine sex and ethnicity of our ancestors that helps historians to compose a complete picture of their life and customs. In the region of Altai Mountains archaeologists discovered remains of an ancient civilisation. During excavations, they found many bones of newborns and wondered what happened there. The scientists have suggested that selective infanticide was accustomed in this culture, when all female or male newborns were killed.
The bone samples were handed over to a research team headed by Andrew Poltoraus from the Institute of Molecular Biology. The scientists drilled tiny holes in each sample and collected bone shavings. This small amount of bone tissues is enough to define the primary DNA sequence. For molecular and genetic analysis there is no need to decoder all the DNA, only its fragments. Firstly, it is necessary to multiply these fragments using the polymerase chain reaction (PCR). Then an automatic sequenator deciphers sequences of nucleotides in each fragment.
To define sex the researchers use the gene of amylogenine situated in sex chromosomes. In X-chromosome this gene is shorter in Y-chromosome. So, if PCR gives gene fragments of the same length (e.g. 106 bases), the remains probably belong to a female being (women have two X-chromosomes). If there are fragments of two lengths, e.g. of 106 and 112 bases, the studied remains belong to a male (with X and Y-chromosomes). "All the analysed samples were female", says Eugeny Kulikov, a participant of the study. "This means that in the Altai culture baby-girls were killed".
To define the ethnic group the scientists analysed the mitochondrion DNA situated not in the nucleus of cells but in mitochondria too. Mitochondrial DNA has a fragment of hypervariability which usually differs in different ethnoses. After studying DNA from the Altai bones the biologists found that all the newborns in this burial place were girls of one ethnic group.
The researchers can also identify diseases of ancient humans because genes of ribosomal DNA of each bacterium have their own original primary sequence. DNA exists not only in remains of humans and animals but also in objects made from natural materials so the scientists can say which bones our ancestors used for making their tools and what kind of fur for their clothes.
For PCR analysis only small DNA amount is needed, but it should be in more or less good condition. But if somebody says he can sequenate DNA of a dinosaur, it's only a tale because all dinosaur bones are for a long time fossils.
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