Genetic diversity among Canadienne, Brown Swiss, Holstein and Jersey cattle based on mitochondrial D-loop sequence variation
Academic Article
Overview
Research
Identity
Additional Document Info
Other
View All
Overview
abstract
Polymorphisms creating 36 unique haplotypes were observed with in breeds at 55 sites in the displacement loop (D-loop) region of the mitochondrial DNA (mtDNA) consisting of 814 bp. The majority (56%) of the differences observed were the result of nucleotide substitution events with 19 transitions, 12 transversions, 11 deletions, 12 insertions and 1 inversion. In all cases, the insertions and deletions were of a single nucleotide. Canadienne cattle were found to have 60% unique haplotypes within the population compared to 89% in Brown Swiss, 90% in Holstein and 100% in Jersey cattle, possibly reflecting the narrow genetic base in the Canadienne breed. The degree of sequence divergence in the D-loop region of mtDNA was based on samples from 20 Canadienne, 9 Brown Swiss, 10 Holstein and 10 Jersey cattle and a phylogenetic analysis showed that these cattle (Bos taurus) were not evolutionarily distinct. All four breeds grouped together when a strict consensus tree was generated. Intra-breed variability proved to be high for the Canadienne, Holstein and Jersey breeds (5773%) but not the Brown Swiss breed (29%). The Canadienne and Brown Swiss (45%), and Brown Swiss and Holstein (43%) showed the lowest degree of inter-breed variability. The greatest variability among the four breeds was between Canadienne and Jersey (80%) cattle. These findings question the validity of phenotypic assessment of genetic diversity, such as Canadienne cattle being described as Black Jersey. Key words: Genetic distance, phylogenetic analysis, D-loop sequence, cattle
