Human Chromosome 2 is a fusion of two ancestral chromosomes

I found an interesting article from Evolution Pages that explains not just the difference in the DNA string of a Human and that of a Chimpanzee, but also how that genetic string changed.

All great apes apart from human have 24 pairs of chromosomes.

There are 23 paired chromosomes in human DNA. A chromosome is a very long DNA molecule and associated proteins, that carry portions of the hereditary information of an organism.

There is therefore a hypothesis that the common ancestor of all great apes had 24 pairs of chromosomes and that the fusion of two of the ancestor's chromosomes created chromosome 2 in humans. The evidence for this hypothesis is very strong.

Not only is this strong evidence for a fusion event, but it is also strong evidence for common ancestry; in fact, it is hard to explain by any other mechanism.

Let us re-iterate what we find on human chromosome 2. Its centromere is at the same place as the chimpanzee chromosome 2p as determined by sequence similarity. Even more telling is the fact that on the 2q arm of the human chromosome 2 is the unmistakable remains of the original chromosome centromere of the common ancestor of human and chimp 2q chromosome, at the same position as the chimp 2q centromere (this structure in humans no longer acts as a centromere for chromosome 2.

Very cool stuff, but for more detailed information please read the full article.

Read the article