title: Whole-genome analysis of animal A- and B-type cyclins.
abstract: BACKGROUND
  Multiple A- and B-type cyclins have been identified in animals, but their study is complicated by varying degrees of functional redundancy. A non-essential phenotype may reflect redundancy with a known or as yet unknown gene. Complete sequencing of several animal genomes has allowed us to determine the size of the mitotic cyclin gene family and therefore to start to address this issue.
  
  
  RESULTS
  We analyzed the Caenorhabditis elegans, Drosophila melanogaster and Homo sapiens genomes to identify known and novel A- and B-type cyclin genes and distinguish them from related pseudogenes. We find only a single functional A-type cyclin gene in invertebrates but two in vertebrates. In addition to the single functional cyclin A gene, the C. elegans genome contains numerous cyclin A pseudogenes. In contrast, the number and relationship of B-type cyclins varies considerably between organisms but all contain at least one cyclin B1-like gene and a cyclin B3 gene.
  
  
  CONCLUSIONS
  There are three conserved families of mitotic cyclins in animals: A-, B3- and B-type. The precise number of genes within the A- and B-type families varies in different organisms, possibly as an adaptation to their distinct developmental strategies.
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, UK.
authors.forename: Conrad A
authors.initials: CA
authors.lastname: Nieduszynski
authors.forename: James
authors.initials: J
authors.lastname: Murray
authors.forename: Mark
authors.initials: M
authors.lastname: Carrington
mesh_terms: D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D015139:Blotting, Southern; D017173:Caenorhabditis elegans / Q000235:genetics*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics; D019925:Cyclin A / Q000235:genetics*; D019926:Cyclin B / Q000235:genetics*; D029721:Drosophila Proteins / Q000235:genetics; D004331:Drosophila melanogaster / Q000235:genetics*; D016678:Genome; D015894:Genome, Human; D006801:Humans; D008969:Molecular Sequence Data; D010802:Phylogeny; D011544:Pseudogenes / Q000235:genetics; D016415:Sequence Alignment
chemical_list: D029742:Caenorhabditis elegans Proteins; C503698:CycB protein, Drosophila; D019925:Cyclin A; D019926:Cyclin B; D029721:Drosophila Proteins