جستجوی مقالات مرتبط با کلیدواژه « genetic variation » در نشریات گروه « علوم دام »

The majority of selection and breeding programs for sheep focus on improving weight and growth traits. Body weight uniformity is a crucial economic characteristic within the industry of sheep breeding. Birth weight is an important trait that has an optimal limit, and extremely high or extremely low birth weight can cause difficulties during birth, stillbirth, and problems such as dystocia, stillbirths, and diminished growth of lambs. The existence of genetic variability for the residual variance is a necessary condition for improving this trait through breeding. Recent studies have demonstrated that the residual variance is governed by additive genetic influences. The enhancement of uniformity in body weight traits can be achieved as an economic advantage by employing selection strategies that take into account the genetic variability of the residual variance. The present study was undertaken to ascertain variance components and genetic parameters pertaining to the residual variance of birth weight and weaning weight traits in Sangsari sheep. Also, the genetic correlation between these traits and their residual variance was calculated.

To carry out this study, the phenotypic data of 5986 lambs obtained between 1986 and 2016 from the Sangsari sheep breeding station were utilized. The traits examined comprised birth weight, weaning weight, and the residual variance associated with them. To incorporate fixed factors into the model and assess their impact on the examined traits, a least-squares analysis was conducted utilizing the GLM procedure of SAS software. The estimation of variance components and genetic parameters was conducted using the average information restricted maximum likelihood (AI-REML) algorithm implemented in the DMU software, employing the DHGLM method. Firstly, an animal model was applied to estimate the residual variance of birth weight and weaning weight traits. Following that, a bivariate model was employed to examine the influence of additive genetic effects on the residual variance.

The additive genetic standard deviations for the residual variance of birth weight and weaning weight were determined to be 7.74 and 17.90, respectively, consequently, a decrease of one standard deviation in the breeding value of residual variance resulted in a reduction of 7.74 and 17.90% in the uniformity of the respective traits. The heritability estimates for the mean and residual variance of birth weight and weaning weight were found to be 0.26 ± 0.09, 0.059 ± 0.003, 0.23 ± 0.06, and 0.037 ± 0.001, respectively. The genetic coefficient of variation was determined to be 0.58 for birth weight and 0.48 for weaning weight. The genetic correlation ranged from -0.16 for birth weight and residual variance to 0.11 for weaning weight and residual variance.

The results of the current study offer crucial information regarding the presence of additive genetic variation for the residual variance of birth weight and weaning weight within Sangsari sheep herds, which can be utilized to enhance uniformity by selecting for reduced residual variance. The selection for increasing birth weight resulted in a reduction of the breeding value of residual variance and an enhancement of herd uniformity, owing to the favorable genetic correlation observed between birth weight and its residual variance. The genetic correlation for weaning weight was found to be unfavorable, indicating that selecting for higher weaning weights led to increased heterogeneity within the herd.

The aim of this study was to identify the genome-wide copy number variations (CNV) in one of the sheep breeds in Afghanistan named Arabic breed, and to study the associations between these regions containing this kind of diversity with different biological pathways. For this purpose, 15 animal samples from different ages were collected from their natural rearing environment in Herat province of Afghanistan and then were genotyped using Illumina Ovine 50kSNP array. After various steps of the data quality control, the genome-wide detection of CNVs was carried out using Hidden Markov Model in PennCNV (version 1.0.3) software. The results showed that all animals used in this study have CNVs in their genome. In total, 306 CNVs were observed for autosomal chromosomes. The total genomic length of CNVs was 128 Mbp and the average CNV numbers per animal was 20.4. After merging overlapped regions, a total of 286 CNVR regions were identified. These genomic regions were then further evaluated using bioinformatics tools for identifying the metabolic pathways associated with them. The results of gene ontology study indicated that many of these regions are associated with different metabolic pathways such as fertility and reproductive performance, body weight and carcass characteristics, immune system development, and skeletal-muscular system.

Due to their roles in regulating embryonic growth and development  members of DNA Methyltransferases (DNMTs) family have been shown to play fundamental parts in  embryonic fertilization to postnatal life; through regulating the establishment and/or maintenance of specific epigenetic marks. The present study was conducted to identify potential reported mutations within the exon 33 of DNMT-1, introns 4 of DNMT-3a and introns 3 DNMT-3a genes and their relationship with birth weight in Iranian Holstein cows. A total of 60 blood samples from Holstein dairy cattle with records of weight from birth to adult age were randomly collected from industrial dairy cattle farm located in Kerman province. Genomic DNA samples was extracted using Phenol-Chloroform method and target sequence was amplified with PCR using specific primers. Polymerase chain reaction-single stranded conformational polymorphism (PCR-SSCP) and silver nitrate staining methods was used for screening potential mutation in target sequences. According to results of this study, in all cases, no mutation in target sequence were identified as all samples had the same specific SSCP pattern with respect to their size. The lack of polymorphism may imply that these region may be attributable to a relative inefficiency of PCR-SSCP for mutation detection, small sample size, stochastic effects of genetic drift and/or conserved nature of these genes due to either natural or artificial selection. According to the results of this study, analyzed sequence may not be informative as molecular marker for birth weight in Holstein cattle.

Due to the importance of conservation and preserving indigenous breeds, Baluchi sheep as the most populous breed of Iranian sheep with reliable pedigree was selected. In this study genetic variations were analyzed with 15 microsatellites markers (BM737, BM1815, BMS332, BMS995, BMS2721, KD101, LSCV36, LSCV38, McM63, McM139, McM214, McMA1, McMA10, OarVH110, TGLA231) in a population of Baluchi sheep. Whole blood samples were randomly collected from 140 sheep at Abbas Abad Breeding Station (Mashhad). After PCR reactions, McM139 locus wasn't amplified and LSCV38 locus was ignored for many null Alleles. Thirteen microsatellites loci were %100 polymorphic. Number of alleles, observed and expected heterozygosity, polymorphic information content (PIC) and Shannon index were calculated. Highest and lowest allele numbers was observed in OarVH110 locus with 12 alleles and 6 alleles in BM737, BMS332, McMA10, respectively. Effective number of allele was between 3.51 (LSCV36) to 8.66 (OarVH110). The highest and the lowest heterozygosity belonged to 0.89 (OarVH110) and 0.71 (LSCV36), respectively. OarVH110 locus indicated the highest PIC (0.873) and LSCV36 locus indicated the lowest PIC (0.669). The highest and lowest Shannon index were belonged to 2.21 (OarVH110) and 0.66 (LSCV36), respectively. These results verify high efficiency of microsatellites marker for screening of population's structure in Iranian native sheep and in future study for QTL mapping. So, presence of new alleles and allele range indicates difference between Baluchi sheep population structure with foreign Sheep breeds.

In this study, the genetic variation in Zandi sheep was investigated using 15 microsatellite markers. Genomic DNA was extracted from 120 Blood samples, using modified salting-out method. All of fifteen loci were amplified successfully and all tested loci were all polymorphic. The Tests of genotype frequencies for deviation from the Hardy-Weinberg equilibrium (HWE) were performed at each locus and revealed significant departure from HWE (P<0.001) due to heterozygote excess.Parameters of variability such as effective number of alleles and gene diversities (Heterozygosity) corroborated the high level of variation frequently displayed by microsatellite markers. Furthermore, other criteria of genetic variation including PIC values and Shanon information index had calculated in this study. The mean of polymorphism information content of the Zandi sheep population was equal to 0.808 and indicate high level of polymorphism. Also the Shannon's information index of the Zandi sheep population was high (1.92 ± 0.09). Based on results of this research, high level of genetic diversity was observed in Zandi breed. This research also was shown that microsatellite markers is a useful tool for evaluation of genetic variation among of domesticated animals.

This study investigated genetic variation within indigenous chicken of Khorasan using four microsatellite markers (MCW5, MCW16, MCW18 and MCW34). 90 blood samples were collected from this population and phenol-chloroform extraction method was used to isolate the DNA. The highest and the lowest allele number and effective alleles are shown in MCW5 (6 and 5.293) and MCW34 (4 and 3.138), respectively. The expected heterozygosis varied from 0.8157 (MCW5) to 0.6854 (MCW34). The amount of genetic variation within this population was found 0.74 this could be due to low inbreeding in this population. The Hardy-Weinberg equilibrium (HWE) test showed that all loci deviated from HWE (p