<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Ayala, F J</style></author><author><style face="normal" font="default" size="100%">Rich, S M</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Genetic variation and the recent worldwide expansion of Plasmodium falciparum.</style></title><secondary-title><style face="normal" font="default" size="100%">Gene</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Gene</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Animals</style></keyword><keyword><style  face="normal" font="default" size="100%">Antigens, Protozoan</style></keyword><keyword><style  face="normal" font="default" size="100%">Base Sequence</style></keyword><keyword><style  face="normal" font="default" size="100%">Genetic Variation</style></keyword><keyword><style  face="normal" font="default" size="100%">Merozoite Surface Protein 1</style></keyword><keyword><style  face="normal" font="default" size="100%">Molecular Sequence Data</style></keyword><keyword><style  face="normal" font="default" size="100%">Phylogeny</style></keyword><keyword><style  face="normal" font="default" size="100%">Plasmodium</style></keyword><keyword><style  face="normal" font="default" size="100%">Plasmodium falciparum</style></keyword><keyword><style  face="normal" font="default" size="100%">Polymorphism, Genetic</style></keyword><keyword><style  face="normal" font="default" size="100%">Protozoan Proteins</style></keyword><keyword><style  face="normal" font="default" size="100%">Repetitive Sequences, Nucleic Acid</style></keyword><keyword><style  face="normal" font="default" size="100%">RNA, Ribosomal</style></keyword><keyword><style  face="normal" font="default" size="100%">Sequence Homology, Nucleic Acid</style></keyword><keyword><style  face="normal" font="default" size="100%">Species Specificity</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2000</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2000 Dec 30</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">261</style></volume><pages><style face="normal" font="default" size="100%">161-70</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Plasmodium falciparum, the agent of human malignant malaria, diverged from Plasmodium reichenowi, the chimpanzee parasite, about the time the human and chimpanzee lineages diverged from each other. The absence of synonymous nucleotide variation at ten loci indicates that the world populations of P. falciparum derive most recently from one single strain, or 'cenancestor,' which lived a few thousand years ago. Antigenic genes of P. falciparum (such as Csp, Msp-1, and Msp-2) exhibit numerous polymorphisms that have been estimated to be millions of years old. We have discovered in these antigenic genes short repetitive sequences that distort the alignment of alleles and account for the apparent old age of the polymorphisms. The processes of intragenic recombination that generate the repeats occur at rates about 10(-3) to 10(-2), several orders of magnitude greater than the typical mutational process of nucleotide substitutions. We conclude that the antigenic polymorphisms of P. falciparum are consistent with a recent expansion of the world populations of the parasite from a cenancestor that lived in tropical Africa a few thousand years ago.</style></abstract><issue><style face="normal" font="default" size="100%">1</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/11164047?dopt=Abstract</style></custom1></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Rich, S M</style></author><author><style face="normal" font="default" size="100%">Ferreira, M U</style></author><author><style face="normal" font="default" size="100%">Ayala, F J</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The origin of antigenic diversity in Plasmodium falciparum.</style></title><secondary-title><style face="normal" font="default" size="100%">Parasitol Today</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Parasitol. Today (Regul. Ed.)</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Amino Acid Sequence</style></keyword><keyword><style  face="normal" font="default" size="100%">Animals</style></keyword><keyword><style  face="normal" font="default" size="100%">Antigens, Protozoan</style></keyword><keyword><style  face="normal" font="default" size="100%">Base Sequence</style></keyword><keyword><style  face="normal" font="default" size="100%">Genes, Protozoan</style></keyword><keyword><style  face="normal" font="default" size="100%">Genetic Variation</style></keyword><keyword><style  face="normal" font="default" size="100%">Merozoite Surface Protein 1</style></keyword><keyword><style  face="normal" font="default" size="100%">Molecular Sequence Data</style></keyword><keyword><style  face="normal" font="default" size="100%">Plasmodium falciparum</style></keyword><keyword><style  face="normal" font="default" size="100%">Protozoan Proteins</style></keyword><keyword><style  face="normal" font="default" size="100%">Sequence Homology</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2000</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2000 Sep</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">16</style></volume><pages><style face="normal" font="default" size="100%">390-6</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Most studies of genetic variability of Plasmodium falciparum have focused on protein antigens and the genes that encode them. The consensus is that populations exhibit high levels of genetic polymorphism, most notably the genes encoding surface proteins of the merozoite (Msp1, Msp2) and the sporozoite (Csp). The age and derivation of this variation is a subject that warrants further careful consideration, as discussed here by Stephen Rich, Marcelo Ferreira and Francisco Ayala.</style></abstract><issue><style face="normal" font="default" size="100%">9</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/10951599?dopt=Abstract</style></custom1></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Rich, S M</style></author><author><style face="normal" font="default" size="100%">Hudson, R R</style></author><author><style face="normal" font="default" size="100%">Ayala, F J</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Plasmodium falciparum antigenic diversity: evidence of clonal population structure.</style></title><secondary-title><style face="normal" font="default" size="100%">Proc Natl Acad Sci U S A</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Proc. Natl. Acad. Sci. U.S.A.</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Amino Acid Sequence</style></keyword><keyword><style  face="normal" font="default" size="100%">Animals</style></keyword><keyword><style  face="normal" font="default" size="100%">Antigens, Protozoan</style></keyword><keyword><style  face="normal" font="default" size="100%">Molecular Sequence Data</style></keyword><keyword><style  face="normal" font="default" size="100%">Phylogeny</style></keyword><keyword><style  face="normal" font="default" size="100%">Plasmodium falciparum</style></keyword><keyword><style  face="normal" font="default" size="100%">Polymorphism, Genetic</style></keyword><keyword><style  face="normal" font="default" size="100%">Protozoan Proteins</style></keyword><keyword><style  face="normal" font="default" size="100%">Recombination, Genetic</style></keyword><keyword><style  face="normal" font="default" size="100%">Sequence Homology, Amino Acid</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1997</style></year><pub-dates><date><style  face="normal" font="default" size="100%">1997 Nov 25</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">94</style></volume><pages><style face="normal" font="default" size="100%">13040-5</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Plasmodium falciparum, the agent of malignant malaria, is one of mankind's most severe scourges. Efforts to develop preventive vaccines or remedial drugs are handicapped by the parasite's rapid evolution of drug resistance and protective antigens. We examine 25 DNA sequences of the gene coding for the highly polymorphic antigenic circumsporozoite protein. We observe total absence of silent nucleotide variation in the two nonrepeated regions of the gene. We propose that this absence reflects a recent origin (within several thousand years) of the world populations of P. falciparum from a single individual; the amino acid polymorphisms observed in these nonrepeat regions would result from strong natural selection. Analysis of these polymorphisms indicates that: (i) the incidence of recombination events does not increase with nucleotide distance; (ii) the strength of linkage disequilibrium between nucleotides is also independent of distance; and (iii) haplotypes in the two nonrepeat regions are correlated with one another, but not with the central repeat region they span. We propose two hypotheses: (i) variation in the highly polymorphic central repeat region arises by mitotic intragenic recombination, and (ii) the population structure of P. falciparum is clonal--a state of affairs that persists in spite of the necessary stage of physiological sexuality that the parasite must sustain in the mosquito vector to complete its life cycle.</style></abstract><issue><style face="normal" font="default" size="100%">24</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/9371796?dopt=Abstract</style></custom1></record></records></xml>