In spite of much comparative work, an uncertainty persists about the branching order of lineages leading to humans, chimpanzees, gorillas, and perhaps also orangutans and gibbons. Even molecular approaches failed to resolve unambiguously the evolutionary tree, the failure resulting from the small amount of differences encountered among the nuclear genes such as globins of closely related species. Fast evolving mitochondrial genes, on the other hand, cannot be taken as a reliable measure for the evolution of species, because they are maternally inherited and the evolutionary biology of cytoplasmic and nuclear genes may be quite different. It is proposed to construct an evolutionary tree for the primates, based on molecular evolution of the nuclear genes for Alpha-fetoprotein and serum ablumin. We have recently determined the structure of these two human genes and localized them to q11-22 of human chromosome 4. A comparison of the sequence data for different species revealed that Alpha-fetoprotein evolves at a very fast rate, approaching that of mitochondrial DNA. The project will involve: (a) the isolation of the albumin and Alpha-fetoprotein genes from the above primates, except man (already done), (b) DNA sequence determination of both genes from above primates (in humans, work in progress), (c) localization of both genes on the primate chromosomes, (d) construction of an evolutionary tree for humans and related primates. The genes will be cloned, starting with DAN obtained from peripheral blood. The DNA will be cleaved with restriction enzymes, then in vitro packaged into a phage Gamma cloning vector. The existing human DNA clones will serve as hybridization probes to screen for the primate genes. DNA sequence analysis will be performed by established methodologies, chromosomal localization of the genes will be accomplished by in situ hybridization of cloned DNA to metaphase chromosomes. The results are expected to give: (a) an accurate phylogenetic tree for the primates, for the first time based on single-copy nuclear genes with high evolutionary rates, (b) a more accurate chromosomal localization of both genes; the latter expectation is based on the existence of chromosomal translocations within qll-22 between man, chimpanzee, gorilla, and orangutan, (c) a potential identification of DNA sequences where chromosomal translocations took place, an event that could be involved in the process of speciation, and (d) a potential identification of newly evolved repetitive sequences which could be implicated in primate evolution.
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