Algorithms|Analysis of Variance|Codon|Computer Simulation|Databases, Nucleic Acid|Decision Trees|Evolution, Molecular|Genes, gag|Genetic Variation|HIV|HIV Core Protein p24|HIV Infections|HLA Antigens|Humans|Linkage Disequilibrium|Mutation|Peptide Fragments|Phylogeny|Selection, Genetic|T-Lymphocytes, Cytotoxic|env Gene Products, Human Immunodeficiency Virus