FIGURE 8-39 Evolution of primate chromosomes. (a) Chromosome paint probes (yellow) for chromosome 16 of the tree shrew (T. belangeri, distantly related to humans) hybridized to tree shrew metaphase chromosomes (red). (b) The same tree shrew chromosome 16 paint probes hybridized to human metaphase chromosomes. (c) Proposed evolution of human chromosomes (bottom) from the chromosomes of the common ancestor of all primates (top). The proposed common primate ancestor chromosomes are numbered according to their sizes, with each chromosome represented by a different color. The human chromosomes are also numbered according to their relative sizes and labeled with colors taken from the colors of the proposed common primate ancestor chromosomes from which they were derived. Small numbers to the left of the colored regions of the human chromosomes indicate the number of the ancestral chromosome from which the region was derived. Various human chromosomes were derived from the proposed chromosomes of the common primate ancestor without significant rearrangements (e.g., human chromosome 1); by fusion (e.g., human chromosome 2 by fusion of ancestral chromosomes 9 and 11); by breakage (e.g., human chromosomes 14 and 15 by breakage of ancestral chromosome 5); or by chromosomal translocations (e.g., a reciprocal translocation between ancestral chromosomes 14 and 21 generated human chromosomes 12 and 22).

[Parts (a) and (b) republished with permission of Springer, from Muller, S., et al., “Defining the ancestral karyotype of all primates by multidirectional chromosome painting between tree shrews, lemurs and humans,” Chromosoma, 1999, 108(6):393-400; permission conveyed through Copyright Clearance Center. Part (c) data from L. Froenicke, 2005, Cytogenet. Genome Res. 108:122.]