MadSci Network: Genetics

Re: How many chromosomes did the ape/human common ancestor have?

Date: Thu Jan 13 14:31:29 2000
Posted By: Michael Onken, MadSci Admin
Area of science: Genetics
ID: 947779581.Ge

The common ancestor of the Human and Chimp lines had 24 pairs of chromosomes. This comes from two observations: first, that chimps, bonobos, gorillas, and orangutans all have 24 pairs of chromosomes, suggesting the change occured specifically within the human lineage; and second, that human Chromosome 2 is homologous to two smaller chimp chromosomes placed end to end. This suggests that the diminution in chromosome number along the path to humans involved a simple translocation that merged the two smaller ape chromosomes into one large human chromosome (chromosomes are numbered from largest to smallest, so chromosome 2 the second largest). No information was gained or lost; it was simply rearranged. For a diagram of this translocation event go to:

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