| Litter size trait is a known most important economic trait, which highly associateswith economic efficiency of the goat industry. The traditional methods of selection forincrease in litter size are limited mainly because of the low heritability, and also, thegenetic progress of it is therefore unstable and slow. With the development of moleculartechniques, the developing MAS/MAI strategy and technique provide new opportunitiesfor the genetic improvement in reproductive traits. Two major genes affecting ovulationhad been identified in some sheep populations, and then more and more evidences of newfecundity genes has been found in other sheep breeds. There has been few publishedstudy of major gene for the same trait in goat so for.In present study, Inhibin gene, INHA, INHBB and INHBA, were studied as strongcandidate for goat fecundity gene based on its important roles in ovaries. Boer, Matou,Haimen and Nubian were chosen as study populations because of both their highreproduction and good meat. The litter sizes of a total of 380 animals were analyzed todetermine whether the genes explain responses in litter size within populations.The possible genetic polymorphisms in majority of the three genes with an emphasisin INHA gene were detected and selectively genotyped using PCR-SSCP-sequencingmethod and PCR-RFLP test respectively, Chi-square test for the homogeneity of allelicdistribution was carried out and the effect of locus as a fixed effect on the litter size usinga fixed model was preliminary estimated using GLM procedures of SAS (v8.1) within thepreliminary populations samples. Additionally, linkage disequilibrium and possiblehaplotype were assessed within the gene for selection of polymorphism for genotyping infurther work. The results were as follows:1. Twelve polymorphisms within INHA gene consisted of -522C＞G, -506-＞G,-446C＞T, -155C＞T, -65G＞C, 129G＞A, 567G＞A, 651A＞G, 792T＞C, 906C＞T, 911T＞Cand 946A＞C are exist in the study goat breeds, which are highly likely common onesamong them. The polymorphisms at 911 and 946 result in change in expressed aminoacids respectively (i.e., 299Val＞Ala and 311Thr＞Pro). Additionally, the SSCP resultsalso indicated any possible polymorphisms within INHBB and INHBA.2. Three loci, -446C＞T, 651A＞G and 946A＞C, were statistically associated withlitter size of the second parity within both Matou and Nubian, Boer and Matou,respectively.3. All populations were in Hardy-Weinberg equilibrium at all genotyping lociwithout zeros in the observational cells of the contingency table, except Boer population at -446C＞T, 651A＞G and 792T＞C loci, Haimen population at -155C＞T, 129G＞A and651A＞G (P＜0.05). Distributions for polymorphisms at all found but -506-＞G,-155C＞Tand 651A＞G loci were significantly assocated with populations (P＜0.05).4. A common positive consistent genotype between 567G＞A and 911T＞C wasdirectly seen within and among all four breed populations except 3 exceptions to thispattern, which suggests that 567A allele is in complete linkage disequilibrium with 911C.Quantifying for linkage disequilibrium between polymorphisms revealed thatpolymorphism -506-＞G was in linkage disequilibrium with -65G＞C within Boer (r2=0.70,D'=0.98) and Haimen(r2=0.54, D'=0.91).5. A common poyerty (less than three times each) even absence (none unexpectedly)of a total three certain 2-marker combination genotypes, namely, M1M1M2M2,M1M1W2M2 and W1M1M2M2, for many (40-50%) of the pairs of loci above (i.e., both ofloci at -155, -65, and 129, -446 and -65 within exon 1, 651 and 792, 792 and 906, 792 and911, 792 and 946, 906 and 946, and 911 and 946 within exon 2, and -506 and 567, -155and 567, and -65 and 567 across the two exons) was found within Boer and Haimensamples. Such poverties suggest that the haplotype frameworks with co-occurrence of two"mutate-type" alleles are lack for those pairs within those populations. Within Nubiansample, whereas, all 9 (32=9) theoretical 2-marker genotype combinations for loci at -446and -65 were seen; also, the total three absent genotype combinations which were presentin neither 55 Haimen ewes nor 209 Boer ewes had a total 29.7% frequency, whichappeared close to normal distributions (3/9=33.3% theoretically). |
