**4.4 Cytochrome b gene**

*Landraces - Traditional Variety and Natural Breed*

*Incomplete stop signals are denoted by lowercase letters.*

*Features of the* Ovis aries *mitochondrial genomea*

tRNA-Pro (L) 15,371 15,436 66 Control region 15,437 16,616 1,180

**Feature From To Size Start** 

Dymova et al. [51] carried out archeological mitochondrial DNA D-loop fragment analysis based on about 4,000–1,000 years old sheep bone remains in Altai. They found all the previously determined haplogroups (A, B, C, D and E lineages). That richness of diversity led them to conclude that the Altai region had been a

 *[45].*

*Nucleotide number 1 is the 5′ end of the tRNA-Phe-specifying gene. Anticodons for the two tRNA-Leu and the two tRNA-Ser are given in parentheses. (L) denotes light-strand sense. Positions include the 58 and 38 nt of each feature. ATPase6 and ATPase8, genes encoding subunits 6 and 8 of ATPase; COI-III, genes encoding subunits I–III of cytochrome c oxidase; Cyt b, gene encoding cytochrome b; NADH1–6, genes encoding subunits 1–6 of nicotinamide* 

**codon**

**Stop codonb** **3′ spacer**

Study of Horsburgh and Rhines [52] evaluating sheep finds excavated in a South

Mitochondrial displacement-loop (D-loop), called also as control region (CD) is

Divergence times estimated for types B and A (which was about 1.5–0.45 Mya)

can be overestimated when it is based solely on hypervariable sequence of CR [54]. In regard of calibrating a molecular clock, the consideration of the codifying cytochrome b gene seems to be more accurate. To eliminate the distortive effect (known heteroplasmic behavior) of CR the repeat unit located within the CR region

The purpose of sequencing is, in addition to the genetic characterization of a given breed (population), to compare its genetic material to genetic material of other already sequenced breeds (GenBank sequences). Thus, we try to get an answer to the origin of the given breed and its genetic relatives. This is important when studied in the former natural range of the sheep species (primarily Asia, then Europe and Africa), but it is also important on the continents (America and

For example, based on the CR, Annus et al. [55] confirmed the common origin of the Hungarian Tsigai with European sheep after finding that they are belonging to the haplogroup B (with the exception of 6% to the haplogroup A). An example of the latter case is the evaluation of the Mexican Creole sheep carried out by Alonso et

Lancioni et al. [57] discovered relationships of the three Italian Merino-derived

sheep breeds, and obtained that these are representatives of the predominant haplogroup B (99%). Since almost all the animals are carrying an own individual haplotype these are characterized with a diverse genetic background. On the other hand, this processing gives an example of how, despite upgrading (with Merino),

was removed before phylogenetic inference made by Meadows et al. [46].

In comparative study of samples dated primarily by archeological context and ranged from Late Bronze Age, through Iron Age to post-medieval period Rannamäe et al. [53] identified four novel ancient haplotypes specific to Estonia (H3, H4, H5

migratory area for many sheep and peoples in the past.

and H9), and haplogroups A and B in a ratio of one to two.

a frequently investigated sequence in researches, also in sheep.

Australia) where sheep individuals later entered with migrants.

al. [56], which revealed a narrow Iberian maternal origin.

the maternal background (Appeninica) is clearly discernible.

**4.3 Displacement-loop**

*adenine dinucleotide dehydrogenase.*

*a*

*b*

**Table 1.**

African Neolithic Age cave shown their assignation to haplogroup B.

**186**

It was observed cytochrome b (Cyt b) gene is also quite mutable than other mtDNA coding regions. For this reason, phylogenetic studies have used that marker too to investigate the genetic relationships among breeds. By use of cytochrome b gene and displacement-loop together or individually, like before, five haplogroups of sheep can be distinguished from each other [46].

In the phylogenetic sequence analysis based on cytochrome b gene Bunch et al. [58] revealed an about 3.12 million yearlong evolution of true sheep (*Ovis*). On the course of its evolutionary history there have been three major genetic groups developed. Foremost, the Argaliforms (*Ovis ammon*, 2n = 56) and Moufloniforms (*Ovis musimon* or *O. orientalis*, 2n = 54, and Urial/*Ovis vignei* 2n = 58) diverged from the initial ancestral stock 2.3 million years ago and spread on Eurasian continent. The domestic sheep (*Ovis aries*, 2n = 54) descend solely from *O. orientalis*. Second, the snow sheep group (*Ovis nivicola*, 2n = 52) as a variant of Pachyceriforms took their own shape in Eastern Asia from about 1.96 million years ago, then the other variants of Pachyceriforms (*O. canadiensis*, 2n = 54; *O. dalli*, 2n = 54) separated from them at about 1.41 million years ago, and evolved further in North America. Argaliforms are represented by only one species, *O. ammon*. The ancestral karyotype had 2n = 60 chromosomes. During the evolutionary development of variants of the species, also acrocentric fusions of chromosomes are observed.

According to the initial studies (e.g. [59, 60]) haplogroup A predominates in Asian sheep, while haplogroup B predominates in European sheep. Nevertheless, haplogroup C seems to have a wide geographical distribution [61]. Pedrosa et al. [28] and Chen et al. [61] suggested the divergence time of haplogroup C from haplogroup A and B to be approximately 0.42–0.76 million year ago and approximately 0.45–0.75 Mya from the analysis of control region and Cyt b gene sequences, respectively. However, a study of Meadows et al. [46] using 12 protein-coding genes of mtDNA puts the separation between the haplogroups less early (0.59–1.17 Mya between A and B, and 0.26–0.09 Mya between C and E.
