ORGANIZATION AND INFORMATIONAL CONTENT OF THE THEILERIA-PARVA GENOME

When compared with other Apicomplexan organisms, Theileria parva has a n exceptionally small, 10-12 Mbp, genome. There are only 4 chromosomes , each in the Mbp range, and a complete physical map, based on SfiI li nking data, is available for each one. A number of genes and cDNAs hav e been mapped to specific SfiI fragments. Telomeres consist of the sim ple repeat sequence typical of chromosomal ends but sub-telomeric homo logies do not extend beyond 5 kbp. The only dispersed repetitive seque nces identified to date are minisatellites, but these are found on a s ubset of SfiI fragments. There are clusters of distinct multicopy sequ ences which contain ORFs. However, the majority of parasite protein co ding genes are present in a single copy. They have a compact structure , exhibit a bias in codon usage and non-translated regions are small. Introns, if present, are unusually short. Overall, the genome contains remarkably little repetitive, non-coding DNA. The parasite mitochondr ial DNA is linear in structure, has a limited protein coding capacity and fragmented rRNA genes and its telomeres contain inverted repeat se quences. (C) 1998 Published by Elsevier Science B.V. All rights reserv ed.