The Genetic and Phylogenetic Analysis of the D-Loop Region in Mitochondrial Genome of Najdi Goat

The analysis of mitochondrial DNA has been a potent tool in our understanding of evolution, owing to characteristics such as high copy number, apparent lack of recombination, high substitution rate and maternal mode of inheritance. This study aims to carry outgenetic and phylogenetic analysis on the D-Loop region of the mitochondrial genome in Najdi goats and to evaluate the relations between Najdi goats and other goat breeds available in Iran and around the world.

12 blood samples from unrelated Najdi goats from various areas of Khuzestan Province were collected. After extraction of DNA, a 968 nucleotide fragment of the D-loop region of the mitochondrial genome was amplified and sequenced. Then, the fragments were compared to the other breeds submitted in NCBI database. Finally, a phylogenetic tree was constructed using MEGA6 software.  

The results showed that the Najdi goat breed classified into A Haplogroup and has the lowest genetic distance with the breeds of Chinese and Pakistani goats. The results of genetic variation led to the identification of 20 mutations with 5 Haplotypes in Najdi goat population. Moreover, the haplotype, nucleotide diversities and the average number of pairwise differences were estimated as 0.727, 0.009 and 0.540, respectively; which indicates a high diversity in the Nadji goat. The results obtained from Tajima's D show that in the population of the Najdi goat, a balanced natural selection is going on and the frequency of rare alleles in this population is very low.

The genetic diversity of Najdi goats has increased over the years, while the number of livestock in Khuzestan province has decreased. The increase in genetic diversity could be due to crossbreed of this breed with Pakistani breeds and so on. The result of these crossbreeding in the near future will be the extinction of Najdi goats, and this issue requires more attention from the authorities.