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1.
Genetic differentiation among Hereford populations from Britain, Ireland, Sweden, Canada and New Zealand together with six other beef breeds was assessed using blood type polymorphisms. Changes in the genetic structure of the British Hereford population over time were also examined. Loci surveyed were seven red cell antigen systems (A, B, C, F, L, S, Z), and two serum protein loci (transferrin and albumin). Within group variation was measured by the average expected heterozygosity, and between group relationships by genetic distance. There was significant genetic differentiation among Hereford populations from different countries. Differences between Hereford groups, however, were not as large as differences between breeds. There were also significance differences among British herds. The proportion of Canadian genes in the British 'hybrid' population was estimated to have increased from 0·42 (±0·34) in the 1970s to 0·98 (±0·11) in the 1990s. Canadian Hereford groups were found to be less heterozygous than other groups, and replacement of the British population with Canadian animals may lead to loss of variation. Breeding strategies that preserve original native genes in British Hereford populations should be considered by commercial breeders, in order to prevent the long-term loss of genetic variation within the breed.  相似文献   

2.
From approximately 1000 papers with data on protein polymorphism in some 216 breeds of cattle, 10 polymorphic proteins were compared in means and variances of gene frequencies (arcsin p½) for ten well-recognized breed groups for 196 of the breeds. The polymorphic proteins were α-lactalbumin, β-lactoglobulin, caseins (αsl, β and x), serum albumin, transferrin, haemoglobin, amylase I and carbonic anhydrase II. The breed groups were North European, Pied Lowland, European Red brachyceros, Channel Island brachyceros, Upland brachyceros, primigenius-brachyceros mixed, primigenius, Indian Zebu, African Humped (with Zebu admixture), and African Humped (Sanga).
The coherence within groups and the differences between groups are often impressive. Only carbonic anhydrase II fails to differentiate at least some of the major breed groups.
In some cases paradoxical distributions of rare genetic variants can be explained by a more detailed inspection of breed history.
The chemical data support the morphological and geographical divisions of cattle into major breed groups. There are three distinct but related brachyceros groups; for some polymorphisms the two Channel Island breeds, the Jersey and the Guernsey, are quite divergent. Although some authorities have considered the Pied Lowland as primigenius, it is a very distinct breed group.  相似文献   

3.
Previous mitochondrial DNA (mtDNA) studies have suggested that European and Asian pig populations were derived through multiple domestication events. We investigated whether domestic pig populations were derived from distinct ancestors within their respective regions, using eight domestic breeds (five European and three Asian), and also European and Asian wild boar populations. Genomic analyses utilized 21 microsatellite markers (MS) selected for their distribution across the pig genome in addition to the mtDNA D-loop region. The number of alleles per MS loci ranged from 8 (Sw2008) to 16 (S0097 and S0218). Few significant departures from Hardy–Weinberg equilibrium were detected, suggesting the absence of heterozygote deficiencies. Analyses within populations revealed observed mean heterozygosity from 0.48 (Erhualian) to 0.68 (Dutch WB) and an expected mean heterozygosity from 0.53 (Hampshire) to 0.80 (Japanese WB) with effective alleles ranging from 2.28 (Hampshire) to 3.74 (French WB). Wild boar populations demonstrated a higher level of heterozygosity than domestic breeds. Genetic differentiation estimated by fixation indices (FST) ranged from 0.021 (Yorkshire and Duroc) to 0.410 (Meishan and Hampshire) and was consistent with previous mtDNA analysis. Both phylogenetic and principal component analyses revealed a distinct separation of European and Asian derived populations with tight clustering of the European domestic breeds. Conversely, the use of both MS and mtDNA clarified that the Asian populations were comprised of three groups, one represented by Erhualian and Meishan breed, the second represented by Lanyu pigs and the third represented by the Asian wild boars. The current findings support the hypothesis that Asian domestic populations were derived from multiple Asian ancestral origins whereas the European domestic populations represent a single ancestral European lineage.  相似文献   

4.
From approximately 1000 papers with data on protein polymorphism in some 216 breeds of cattle, 10 polymorphic proteins were compared in means and variances of gene frequencies (arcsin p 1/2) for ten well-recognized breed groups for 196 of the breeds. The polymorphic proteins were alpha-lactalbumin, beta-lactoglobulin, caseins (alpha s1, beta and chi), serum albumin, transferrin, haemoglobin, amylase I and carbonic anhydrase II. The breed groups were North European, Pied Lowland, European Red brachyceros, Channel Island brachyceros, Upland brachyceros, primigenius-brachyceros mixed, primigenius, Indian Zebu, African Humped (with Zebu admixture), and African Humped (Sanga). The coherence within groups and the differences between groups are often impressive. Only carbonic anhydrase II fails to differentiate at least some of the major breed groups. In some cases paradoxical distributions of rare genetic variants can be explained by a more detailed inspection of breed history. The chemical data support the morphological and geographical divisions of cattle into major breed groups. There are three distinct but related brachyceros groups; for some polymorphisms the two Channel Island breeds, the Jersey and the Guernsey, are quite divergent. Although some authorities have considered the Pied Lowland as primigenius, it is a very distinct breed group.  相似文献   

5.
Salers are a native French breed used for beef and dairy production that has expanded to all the continents. The Salers breed was introduced to the north of Spain in 1985 with only 15 individuals from France and has successfully increased to over 20 000 animals. Although over time new animals have been imported from France for breeding, it is possible that the limiting number of founder animals could have resulted in a reduction of the genetic diversity found in Spanish Salers. Thus, the purpose of the present study has been to characterize the genetic diversity of Salers breed in Spain and evaluate a possible founder effect due to reduced number of the first reproducers. A total of 403 individuals from 12 Salers herds were analyzed using 12 microsatellite markers and compared with phylogenetically and geographically close related Blonde d’Aquitaine, Limousin and Charolais French breeds but also other 16 European breeds. Microsatellites in Salers were polymorphic, with a mean allelic richness of 5.129 and an expected heterozygosity of 0.621 across loci (0.576 to 0.736 among all breeds). Average observed heterozygosity was 0.618. All the loci fit the Hardy–Weinberg (HW) equilibrium except TGLA227 locus due to a significant deficit of heterozygotes in only one of the herds, probably attributable to a sampling effect. When all loci were combined, Salers inbreeding coefficient did not differ statistically from 0 (FIS=0.005), indicating not significant excess or deficit of heterozygotes (P=0.309). Based in allelic distribution, Salers revealed a frequency of 0.488 in BM2113-131 and 0.064 in BM2113-143 diagnostic alleles, which are specific to the African zebu. These zebu alleles are also found in some French breeds, supported by STR data previously postulated hypothesis of a migration route through Mediterranean route by which North African cattle may have left a genetic signature in southern Europe. Phylogenetic tree and population structure analyses could unambiguously differentiate Salers cattle from the other populations and 10% of the total genetic variability could be attributed to differences among breeds (mean RST=0.105; P<0.01). Mutation-drift equilibrium tests (sign test and Wilcoxon’s sign rank test) were in correspondence to the absence of founder effect when Bonferroni was applied. Gene diversity previously reported in French Salers was comparable with the observed in our population. Thus, high genetic diversity in Spanish Salers highlights the resources of this population, which looks toward future breeding and selection programs.  相似文献   

6.
Immunogenetic and population genetic analyses of Iberian cattle   总被引:1,自引:0,他引:1  
Blood samples were collected from more than 100 animals in each of 2 Spanish cattle breeds (Retinto and De Lidia), 2 Portuguese breeds (Alentejana and Mertolenga), and American Longhorn cattle. All samples for the 4 Iberian breeds were tested for 20 polymorphic systems; American Longhorn were tested for 19 of the 20. For each breed an average inbreeding coefficient was estimated by a comparison of the observed and expected heterozygosity at 7 or 8 codominant systems tested. All breeds had positive values but only 3 breeds had estimates of inbreeding that were statistically significantly different from 0: De Lidia with = 0.17, Retinto with = 0.08 and Mertolenga with f = 0.05. The De Lidia breed especially may be suffering from inbreeding depression since this high value is greater than expected if all of the animals were progeny of half-sib matings. Genetic distances were calculated from the gene frequency data on these 5 breeds plus 9 other European breeds. Analyses of these distances show a closely related group of the 4 Iberian breeds and American Longhorn, confirming the close relationships among the Iberian breeds and the Iberian, probably Portuguese, origin of American Longhorn cattle.  相似文献   

7.
The present-day Sable Island horse population, inhabiting an island off the eastern coast of Canada, is believed to have originated mainly from horses confiscated from the early French settlers in Nova Scotia in the latter half of the 18th century. In 1960, the Sable Island horses were given legal protected status and no human interference has since been allowed. The objective of this study was to characterize the current genetic diversity in Sable Island horses in comparison to 15 other horse breeds commonly found in Canada and 5 Spanish breeds. A total of 145 alleles from 12 microsatellite loci were detected in 1093 horses and 40 donkeys. The average number of alleles per locus ranged from 4.67 in the Sable Island horse population to 8.25 in Appaloosas, whereas the mean observed heterozygosity ranged from 0.626 in the Sable Island population to 0.787 in Asturcons. Various genetic distance estimates and clustering methods did not permit to support that the Sable Island horses originated from shipwrecked Spanish horses, according to a popular anecdote, but closely resemble light draft and multipurpose breeds commonly found in eastern Canada. Based on the Weitzman approach, the loss of the Sable Island horse population to the overall diversity in Canada is comparable or higher than any other horse breed. The Sable Island horse population has diverged enough from other breeds to deserve special attention by conservation interest groups.  相似文献   

8.
Allozyme electrophoresis (horizontal starch gel and PAGE) and histochemical staining techniques were used to study the genetic composition of an endemic southern African domestic dogCanis familiaris Linnaeus, 1758, the Africanis breed. Genetic differentiation was analysed at 21 protein-coding loci. The results were compared to those for three other populations/breeds: representatives of established Western breeds, crossbred dogs of Western descent from rural areas in South Africa, and indigenous Saluki dogs from the Middle East. Nine polymorphic loci were found (Ak-1,-2, Ck, Per, Hb, Po-A-1 to-3 andPo-Tf). Two unique alleles at theCk andPo-A-2 loci separated the Africanis breed from the other groups. There were also significant differences between Africanis and the other breeds in pair-wise comparisons of allelic frequencies at polymorphic loci. An assignment test, fixation index values, gene flow and genetic distance values indicated a closer genetic association between the Africanis and Saluki breeds than with dogs of Western origin. This finding supports archaeological evidence that the endemic Africanis breed was introduced from the Middle East into Africa thousands of years ago, and not through later western influences. The average heterozygosity ranged from 0.106–0.15, with least heterozygosity in the Africanis and most in the rural crossbred group. The percentage of polymorphic loci, the mean number of alleles per locus (biologically more significant than heterozygosity), and conformation of genotypes to Hardy-Weinberg proportions showed no evidence of recent loss of genetic diversity in Africanis. Genetic differentiation and support of archaeological evidence by genetics indicate that the endemic southern African domestic dog breed is unique.  相似文献   

9.
湖北省三品种猪27个微卫星座位的遗传变异   总被引:43,自引:2,他引:41  
采用国际动物遗传学会(ISAG)和联合国粮农组织(FAO)共同推荐的27个微卫星标记,对湖北省3个主要地方猪种(通城猪、清平猪和阳新猪)的遗传变异进行了检测。计算出各个品种的基因杂合度、各个座位的多态信息含量及品种间的遗传距离。结果表明,3个地方猪种的平均基因杂合度分别为0.7489、0.6987和0.6273,遗传多样性比较丰富;通城猪和清平猪亲缘关系较近,而两者与阳新猪亲缘关系略远。  相似文献   

10.
We estimated the genetic relationships between the endangered German Pustertaler-Sprinzen cattle breed and the Pinzgauer, Vosges and Simmental breeds--decided upon after consultation of the available historical literature. Within-breed diversity of the four breeds was also assessed. Twenty microsatellite markers were amplified in 27-50 unrelated individuals from populations of each breed. Within-breed variation was estimated from average heterozygosity values and mean number of alleles. Breed relationships were evaluated by genetic distance and a neighbour-joining tree was calculated from these estimates. Bootstrap resampling of loci tested the robustness of the tree topology obtained. A tree was also constructed from distance matrices using individual animals as operational taxonomic units. From both the average heterozygosity values and mean number of alleles calculated, the Pustertaler breed appears to be no more genetically impoverished than the other breeds analysed. The breed tree showed an 85% support for the Pustertaler-Pinzgauer grouping, and this result is echoed in the genetic distance values and allele-sharing individual tree.  相似文献   

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