Biology: Mitochondrial DNA
In 1987, a group of scientists published a paper about mitochondrial DNA and the common mitochondrial ancestor that humans all over the world share. Mitochondrial DNA is different from nuclear dna and is only inherited maternally (from mothers, because sperm cells do not contain mitochondria). The DNA stays relatively unchanged throughout generations and the only source of variation is mutation (which occurs at a slow and steady rate). Human mitochondrial DNA codes for around 37 genes (compared to nuclear DNA which codes for around 30,000 genes). The mitochondrial DNA that the scientists tested was from all over the world and can all be traced back to a singular woman who lived (probably in Africa) around 170,000 years ago. This woman is nicknamed “mitochondrial Eve”. The average differences in the mitochondrial dna of the participants of the study was 9.5. The DNA difference within a group (eg. just in Europe) is higher than the difference between groups (eg. between Europe and Asia). It was also found that Africa had the highest number of mutations (probably because that is where the lineage started) and Australia had the lowest number of mutations (because humans immigrated there relatively recently). They claimed in their conclusion that a larger sample size would have given a more definitive answer about the lineage of mtDNA.
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