Why do humans only have 23? What happened to the other chromosome?
Chimp Chr 2q Human chromosome 2 is a fusion of the ancestral Chromosomes 2p and 2q Human Chr 2 Chimp Chr 2p
centromere centromere centromere remnant centromere Human Chimp
telomere DNA remnants telomere DNA Human Chimp
How common are chromosomal fusions? • In humans, about 1 in 1,000 are born with one copy of Chr 13 stuck to a copy of Chr 14 • Fusions can spread in a population if there • are no “costs” • Usually, there are problems in reproduction • (meiosis)
Asian musk shrew (Suncus murinus) Some individuals have 5 fewer chromosomes than others because of fusions – with no detrimental effects