Exhibitions about science and technology are notoriously difficult to keep up-to date because those scientists just won't stop discovering and inventing things! Curator Kate Phillips encountered an example of this last week, after someone spotted a discrepancy between two Melbourne Museum exhibitions, Darwin to DNA (2000) and 600 Million Years: Victoria Evolves (2010).
Both exhibitions compare the similarity of DNA between chimpanzees and humans. The earlier exhibition states that there is less than two per cent difference while the more recent exhibition declares a 96 per cent similarity. While the numbers don't seem to agree, they're not necessarily incorrect because they compare different aspects of the genomes.
Young adult male chimpanzee.
Image: Frans de Waal, Emory University
Source: Used under Creative Commons CC BY-NC-SA 2.0 from Wikimedia Commons.
"The discrepancy comes about because these two exhibitions were developed ten years apart and the understanding of DNA has changed over that time. In 2001 the draft human genome was published and a final version in 2004. In 2005 the draft chimp genome was published and could be accurately compared to the human one. The percentage similarity that came out of this comparison was 96 per cent. Before this time the similarity was probably based on comparing known genes, and therefore was working with less information."
"However the percentage you come up with also depends on how you make the comparison – on which bits of the genome you compare and that could also account for the discrepancy. If you compare genes, we are more similar, if you include the non-coding sequences, we are slightly less similar. Really 98 per cent and 96 per cent are both indicate great genetic similarity."
Chromosomes of a human male. Humans have 23 pairs of chromosomes and chimpanzees have 24 pairs.
Source: National Human Genome Research Institute
We love that someone noticed this because it means that people are reading exhibition text closely, and keeps us on our toes. It's also, as Kate concludes, a pointed demonstration of "the scale of scientific discovery in the area of genome research over the last ten to twenty years."
The Chimpanzee Sequencing and Analysis Consortium (2005) 'Initial sequence of the chimpanzee genome and comparison with the human genome' Nature, Vol 437 pp 69-87. (PDF, 4.3 MB)
Media release from NIH News, 'New Genome Comparison Finds Chimps, Humans Very Similar at the DNA Level' (2005)