Genetic and phylogenetic studies of Chinese native sheep breeds (Ovis aries) based on mtDNA D-loop sequences

To determine the genetic diversity and the origin of Chinese sheep, we analyzed 83 complete sequences of mtDNA D-loop from nine Chinese sheep breeds and a foreign breed, together with nine sheep and cattle available sequences from GenBank. The length of the sequences was considerably variable between 1103 and 1225 bp. The hapolotype diversity was 92.7%. The nucleotide diversity was 3.058%. And the mean nucleotide composition of the 83 sequences was 32.9% A, 29.8% T, 22.9% C and 14.4% G, respectively. The NJ phylogenetic tree (the number of replications of bootstrap test is 1000) revealed that there were three distinct major domestic sheep lineages (termed as lineages A-C) in the 10 breeds. The result indicated that Chinese native sheep breeds derive from three different maternal sources. The mismatch distribution analysis showed that the Fs values were -25.15, -12.28, -8.60 for the lineages A-C, respectively (P<0.01), which suggested that atleast one population expansion events occur in the demographic history of Chinese sheep breeds. (c) 2006 Elsevier B.V. All rights reserved.