Sequence Variation of Bovine Mitochondrial D-loop between Haplotypes of Composite and Hereford Breeds of Beef Cattle

The objective of the study was to know the sequence variation of D-loop region of mitochondrial DNA between haplotypes of Composite and Hereford breeds of beef cattle. The composite breed comprising approximately 1/4 Brahman, Charolais and Friesian, and 1/8 Angus and Hereford. PCR-RFLPs were applied for the detection of DNA polymorphism to reveal their haplotypes, and continued with cloning of amplified product to pCR II vector. PCR selection was done using M13 forward and reverse primers followed with checking the incorporation of insert in the amplified fragment. Cycle sequencing of extension product were then carried out using a dye-labeled terminator cycle sequencing kit. Sequence analysis indicated that the restriction site gains in the D-loop are a T to C transition at position 16273 to create a new Ava II site, and a C to T transition at position 245 to create a new Ssp I site. Comparing to the sequence from Gene bank, both haplotypes indicate their variability, confirming previous finding that D-loop region is the most variable region in mtDNA. Key words : D-loop, mitochondrial DNA, sequence, cattle.