Class Of Genetic Markers Research Articles

Application of Markers Assisted Selection for Striga Hermonthica Resistance on Sorghum (Sorghum bicolor (L.) Moench

Sorghum (Sorghum bicolor L. [Moench]) is a staple food crop for smallholder farmers in arid and semi-arid(ASALs) regions worldwide, feeding over 500 million of the world's most resource-poor. Development of Striga Hermonthica resistant cultivars by conventional breeding is slow and have been hampered by the lack of efficient and reliable screening techniques in breeding programs. Molecular markers that are linked to witchweed resistance can expedite the development of resistant cultivars through the adoption of appropriate marker-assisted selection (MAS) strategies. Marker-assisted selection involves the selection of genotypes carrying a desirable gene(s) via linked markers; through MAS more rapid transfer of traits from donor parents to more elite locally adapted crop cultivars is possible with simple-sequence repeat (SSR) markers which have been initially used to detect polymorphism between the parent cultivars. Although costly to develop relative to some other classes of genetic markers, once developed, analysis by SSR markers is both easy and inexpensive. The highly polymorphic nature (high information content) and other favorable characteristics make them excellent genetic markers for a number of studies including marker-assisted selection and fingerprinting of germplasm collections. In this review, we summarize the molecular markers that are linked to the inheritance trait or low germination stimulant production is one of the recognized mechanisms of witch weed resistance.

Molecular inferences about the genus Hypostomus Lacépède, 1803 (Siluriformes: Loricariidae): a review.

This review compiles and discusses the use of genetic markers applied in the study of the fish genus Hypostomus Lacépède, 1803 (Siluriformes: Loricariidae). The database comprises 51 peer-review articles that were published in the last 52years (1968-2020) and thatapproach analysis based on different classes of genetic markers. The use of cytogenetic and enzymatic markers was predominantly especially in population studies with the genus Hypostomus, while mitochondrial markers were the majority in phylogenetic studies. Although significant methodological advances have occurred for molecular evaluation, they are still modestly applied to the study of neotropical fish genera, in which Hypostomus is included. New perspectives, especially on integrative approaches, are needed to improve our knowledge of thegenetic functionalityof fishes.

Investigation of gene pool and genealogical links between sheep breeds of southern Russia by blood groups and DNA microsatellites

To study the gene pool and the establishment of genealogical relationships between breeds of sheep of different directions productivity bred in Russia, were used two classes of genetic markers - blood and DNA microsatellites. The included sample sheep are fine-wool Merino breeds: Grozny (GR), Caucasian (CA), Manychskij merino (MM), the Soviet Merino (SM), Stavropol (ST) and coarse wool breeds: Edilbaevskaya (ED), Karakul (CR) and Romanov (RO). For the study of erythrocyte, were selected antigens (blood group) in 1159 samples from 11 breeding farms. For microsatellite DNA study - 598 from 10 breeding farms. Microsatellite analysis revealed that the most polymorphic were Stavropol breed sheep that have identified an average of 18.27 alleles per locus were relatively conservative Romanov breed sheep - 9.7 alleles per locus. The minimum genetic distances established between Grozny and Soviet Merino - 0.0569 (for microsatellites) and 0.0741 (blood groups - later in the same sequence). The rocks of the Stavropol - Grozny were 0.0861 and 0, 0810. Whereas Stavropol and Soviet Merino 0.0861 and 0.1094. Also relatively close between Grozny - Edilbaevskoy , Grozny - Karakul, Edilbaevskoy - Karakul: 0.1364 and 0.0851, respectively; 0.1620 and 0.1208; 0.1875 and 0.1192. The highest genetic distances were between Stavropol and Karakul - 0.2664 and 0.1804, as well as between the Romanov and all studied species - 0.2491 ... 0.3211 and 0.1734 ... 0.2235.

Investigating population genetic structure in a highly mobile marine organism: the minke whale Balaenoptera acutorostrata acutorostrata in the North East Atlantic.

Inferring the number of genetically distinct populations and their levels of connectivity is of key importance for the sustainable management and conservation of wildlife. This represents an extra challenge in the marine environment where there are few physical barriers to gene-flow, and populations may overlap in time and space. Several studies have investigated the population genetic structure within the North Atlantic minke whale with contrasting results. In order to address this issue, we analyzed ten microsatellite loci and 331 bp of the mitochondrial D-loop on 2990 whales sampled in the North East Atlantic in the period 2004 and 2007–2011. The primary findings were: (1) No spatial or temporal genetic differentiations were observed for either class of genetic marker. (2) mtDNA identified three distinct mitochondrial lineages without any underlying geographical pattern. (3) Nuclear markers showed evidence of a single panmictic population in the NE Atlantic according STRUCTURE's highest average likelihood found at K = 1. (4) When K = 2 was accepted, based on the Evanno's test, whales were divided into two more or less equally sized groups that showed significant genetic differentiation between them but without any sign of underlying geographic pattern. However, mtDNA for these individuals did not corroborate the differentiation. (5) In order to further evaluate the potential for cryptic structuring, a set of 100 in silico generated panmictic populations was examined using the same procedures as above showing genetic differentiation between two artificially divided groups, similar to the aforementioned observations. This demonstrates that clustering methods may spuriously reveal cryptic genetic structure. Based upon these data, we find no evidence to support the existence of spatial or cryptic population genetic structure of minke whales within the NE Atlantic. However, in order to conclusively evaluate population structure within this highly mobile species, more markers will be required.

Tracking climate change in a dispersal‐limited species: reduced spatial and genetic connectivity in a montane salamander

Tropical montane taxa are often locally adapted to very specific climatic conditions, contributing to their lower dispersal potential across complex landscapes. Climate and landscape features in montane regions affect population genetic structure in predictable ways, yet few empirical studies quantify the effects of both factors in shaping genetic structure of montane-adapted taxa. Here, we considered temporal and spatial variability in climate to explain contemporary genetic differentiation between populations of the montane salamander, Pseudoeurycea leprosa. Specifically, we used ecological niche modelling (ENM) and measured spatial connectivity and gene flow (using both mtDNA and microsatellite markers) across extant populations of P.leprosa in the Trans-Mexican Volcanic Belt (TVB). Our results indicate significant spatial and genetic isolation among populations, but we cannot distinguish between isolation by distance over time or current landscape barriers as mechanisms shaping population genetic divergences. Combining ecological niche modelling, spatial connectivity analyses, and historical and contemporary genetic signatures from different classes of genetic markers allows for inference of historical evolutionary processes and predictions of the impacts future climate change will have on the genetic diversity of montane taxa with low dispersal rates. Pseudoeurycea leprosa is one montane species among many endemic to this region and thus is a case study for the continued persistence of spatially and genetically isolated populations in the highly biodiverse TVB of central Mexico.

Population genetic structure of Mugil cephalus in the Mediterranean and Black Seas: a single mitochondrial clade and many nuclear barriers

The population structure and evolutionary history of Mugil cephalus were investigated across 18 sampling sites in the NE Atlantic Ocean, Mediterranean and Black Seas, us- ing 2 classes of genetic markers: sequence polymorphism of an 857 bp fragment of mitochondrial (mtDNA) cytochrome b, and allele size variation at 7 nuclear loci. The level of nucleotide diversity recovered with the mtDNA marker was very low (~0.6% divergence), indicating the presence of a single clade over the entire area. Mismatch distribution, Bayesian skyline plots and associated sta- tistics revealed a recent demographic crash followed by population expansion, but nuclear data in- dicated population constancy in the area covered in this study. While a single clade was detected, significant mtDNA genetic differentiation was, however, observed between the samples from the Black Sea and the samples from other (sub-) basins (ΦST = 0.17; p = 0.029). The nuclear loci also re- vealed significant genetic differentiation and isolation-by-distance in M. cepha lus. Patterns of ge- netic structure were, however, significantly more pronounced with nuclear than with mtDNA markers; the former indicated the presence of 3 (Bayesian clustering) to 6 (Monmonnier's method) populations. The highest levels of genetic heterogeneity at nuclear markers occurred at the well- known Almeria-Oran Front, but also in the Bosporus Strait. Thus, both sets of markers revealed the importance of this strait as a barrier to gene flow, probably during the Pleistocene. The results also revealed genetic heterogeneity in the eastern Mediterranean basin, and suggested that the popula- tion expanded from this sub-basin towards the Atlantic Ocean and Black Sea.

Multiple-locus variable-number tandem-repeat analysis of Streptococcus pneumoniae and comparison with multiple loci sequence typing

BackgroundStreptococcus pneumoniae infections remain a major cause of morbidity and mortality worldwide. The diversity of pneumococci was first evidenced by serotyping of their capsular polysaccharides, responsible of virulence, resolving into more than 93 serotypes. Molecular tools have been developed to track the emergence and the spread of resistant, hyper virulent or non-vaccine type clones, particularly DNA-based methods using genetic polymorphism. Pulsed-Field Gel Electrophoresis analysis (PFGE) and Multiple Loci Sequence Typing (MLST) are the most frequently used genotyping techniques for S. pneumoniae. MLST is based on sequence comparison of housekeeping genes clustering isolates within sequence types. The availability of genome sequence data from different S. pneumoniae strains facilitated the search for other class of genetic markers as polymorphic DNA sequences for a Multiple-Locus Variable-Number Tandem-Repeat Analysis (MLVA). This study aims at confirming the relevance of MLVA of S. pneumoniae, comparing MLST and MLVA performances when discriminating subgroups of strains belonging to the same Sequence Type (ST), and defining a restricted but universal set of MLVA markers that has at least the same discriminatory power as MLST for S. pneumoniae by applying marker sets used by different authors on 331 isolates selected in UK.ResultsA minimum spanning tree was built including the serotypes distribution and comparing MLVA and MLST results. 220 MLVA types were determined grouped in 10 Sequence Types (ST). MLVA differentiated ST162 in two clonal complexes. A minimal set was defined: ms 25 and ms37, ms17, ms19, ms33, ms39, and ms40 including two universal markers. The selection was based on MLVA markers with a Diversity Index >0.8 and a selection of others depending of the population tested and the aim of the study. This set of 7 MLVA markers yields strain clusters similar to those obtained by MLST.ConclusionsMLVA can discriminate relevant subgroups among strains belonging to the same ST. MLVA offers the possibility to deduce the ST from the MLVA Type. It permits to investigate local outbreaks or to track the worldwide spread of clones and the emergence of variants.

Evidence of multiple vicariance in a marine suture‐zone in the Gulf of Mexico

AbstractAim Our aim was to assess whether single or multiple vicariance event(s) have occurred in a marine suture‐zone in the northern Gulf of Mexico. We estimated the divergence time of two genetically distinct groups of lane snapper (Lutjanus synagris), distributed on either side of this zone, and compared it to the timing of other vicariance events described previously in the area.Location The northern Gulf of Mexico from the Texas coastline to the Atlantic coast of South Florida, USA. The marine suture‐zone is proximal to Mobile Bay in Alabama.Methods A Bayesian Markov chain Monte Carlo (MCMC) approach was used to estimate mutation‐corrected divergence and genetic migration between eastern and western groups of lane snapper, based on genotypic differences at 13 nuclear‐encoded microsatellites obtained previously from 77 and 171 individual samples, respectively. A second estimate of divergence time for eastern and western groups of lane snapper was generated, based on 590 base pairs of DNA sequence from the mitochondrially encoded NADH dehydrogenase subunit 4 (ND4) obtained previously from 45 and 93 individual samples, respectively.Results Both classes of genetic markers (microsatellites and mtDNA) indicated a fairly recent divergence. Confidence intervals for microsatellite‐based estimates suggested that divergence began less than 21 thousand years ago (ka), while confidence intervals for mitochondrial DNA‐based estimates suggested divergence began less than 130 ka. These estimates were not consistent with vicariance events in the literature, which are hypothesized to have occurred well before 135 ka.Main conclusions These results indicate that the marine suture‐zone in the northern Gulf of Mexico features multiple vicariance events and may be characterized by a complex geological/environmental history. We suggest that processes during or after the Wisconsin glaciation (c. 110–18 ka) may have created a previously unrecognized barrier for lane snapper and possibly other species as well.

Mixed stock analysis and the power of different classes of molecular markers in discriminating coastal and oceanic Atlantic cod (Gadus morhua L.) on the Lofoten spawning grounds, Northern Norway

Atlantic cod (Gadus morhua) encompasses many different populations or stocks, which in part are managed separately. In the northeast Atlantic cod is divided into two main management units; northeast Arctic cod and coastal cod. These two groups have traditionally been separated by otolith classification. In this study, the power of different classes of genetic markers in separating the two cod groups was investigated. The variation in thirteen genetic markers, including allozymes, haemoglobin, the scDNA locus Pantophysin (Pan I) and a number of microsatellites was investigated, and mixed stock analysis and individual assignment tests were performed on samples comprising a mixture of individuals of putative coastal and oceanic type cod. The genetic analyses showed a large genetic differentiation between outer stations and stations located closer to the mainland shore. Mixed stock analysis and individual assignment tests used for estimation of stock proportions gave results similar to those obtained by otolith classification.

Genetic discontinuity associated with an environmentally induced barrier to gene exchange in the marine snail Littorina saxatilis

The geographical genetic structure of 7 populations of the intertidal marine snail Littorina saxatilis with limited dispersal was studied in NW Spain using 3 classes of genetic markers: 840 amplified fragment length polymorphism (AFLP) loci, 3 microsatellites, and 1 morphological trait (shell size). A sharp genetic division at Cape Finisterre, as evidenced by all 3 markers, delimits 2 regions. This genetic discontinuity coincides with an abrupt change in plankton composition, climate and oceanographic characteristics, suggesting that contemporary influences on gene flow associated with the presence of an ecological barrier maintain the genetic subdivision in NW Spain. However, the genetic structure also accords to some extent with an isolation-by-distance model despite the heterogeneous gene flow due to this ecological barrier. Microsatellites and shell size showed a strong and significant covariation in pairwise differences (FST and QST) among populations, but no correlation was found between these markers and AFLPs. Similarly, both microsatellites and shell size showed a higher differentiation between the 2 regions than within each region, but this pat- tern was reversed for AFLPs. Differences in genomic sampling error and homoplasy could account for the discrepancy between different kinds of markers. These results point to the possibility that other marine species may show a similar pattern of intra-specific genetic divergence in NW Spain.

Putative native source of the invasive fire ant Solenopsis invicta in the USA

The ecological and evolutionary dynamics of newly introduced invasive species can best be understood by identifying the source population(s) from which they originated, as many species vary behaviorally, morphologically, and genetically across their native landscapes. We attempt to identify the source(s) of the red imported fire ant (Solenopsis invicta) in the southern USA utilizing data from three classes of genetic markers (allozymes, microsatellites, and mitochondrial DNA sequences) and employing Bayesian clustering simulations, assignment and exclusion tests, and phylogenetic and population genetic analyses. We conclude that the Mesopotamia flood plain near Formosa, Argentina represents the most probable source region for introduced S. invicta among the 10 localities sampled across the native South American range. This result confirms previous suspicions that the source population resides in northern Argentina, while adding further doubts to earlier claims that the Pantanal region of Brazil is the source area. Several lines of evidence suggest that S. invicta in the southern USA is derived from a single location rather than being the product of multiple invasions from widely separated source localities. Although finer-scale sampling of northern Argentina and Paraguay combined with the use of additional genetic markers will be necessary to provide a highly precise source population assignment, our current results are of immediate use in directing future sampling and focusing ongoing biological control efforts.

Patterns of post-glacial colonization by western redcedar (Thuja plicata, Cupressaceae) as revealed by microsatellite markers

As knowledge of historical migration in response to climatic change allows insight into the dynamic nature of range shifts, patterns of post-glacial colonization were evaluated for the western redcedar ( Thuja plicata Donn ex D. Don). We sampled and genotyped 620 trees from 23 populations across its range, including disjunct coastal and interior mesic sites. Genetic variation at eight microsatellite loci (mean alleles/locus = 10.30, mean expected heterozygosity = 0.755) was much higher than previous studies involving other markers, and inbreeding coefficients were predominantly positive (mean = 0.110). The two southernmost populations showed greatest genetic distances, while remaining populations clustered into three distinct geographic groups, comprising northern–coastal, central, and southern–interior populations, respectively. Genetic diversity decreased with latitude, while genetic and geographic distances were strongly correlated (r = 0.788). Our findings are consistent with independent routes of relatively recent colonization from one major refugium, located south of the glacial maximum, rather than ancient vicariant events. Regional bottlenecks, detected in the south of the range, may have resulted from local extinctions as the range of western redcedar advanced northward. Combined with inbreeding and the evolution of inbreeding tolerance, this may have promoted homozygosity for most classes of genetic markers as observed in other studies of this species.

ADAPTIVE POPULATION DIFFERENTIATION IN PHENOLOGY ACROSS A LATITUDINAL GRADIENT IN EUROPEAN ASPEN (POPULUS TREMULA, L.): A COMPARISON OF NEUTRAL MARKERS, CANDIDATE GENES AND PHENOTYPIC TRAITS

A correct timing of growth cessation and dormancy induction represents a critical ecological and evolutionary trade-off between survival and growth in most forest trees (Rehfeldt et al. 1999; Horvath et al. 2003; Howe et al. 2003). We have studied the deciduous tree European Aspen (Populus tremula) across a latitudinal gradient and compared genetic differentiation in phenology traits with molecular markers. Trees from 12 different areas covering 10 latitudinal degrees were cloned and planted in two common gardens. Several phenology traits showed strong genetic differentiation and clinal variation across the latitudinal gradient, with Q(ST) values generally exceeding 0.5. This is in stark contrast to genetic differentiation at several classes of genetic markers (18 neutral SSRs, 7 SSRs located close to phenology candidate genes and 50 SNPs from five phenology candidate genes) that all showed F(ST) values around 0.015. We thus find strong evidence for adaptive divergence in phenology traits across the latitudinal gradient. However, the strong population structure seen at the quantitative traits is not reflected in underlying candidate genes. This result fit theoretical expectations that suggest that genetic differentiation at candidate loci is better described by F(ST) at neutral loci rather than by Q(ST) at the quantitative traits themselves.

Population structure and divergence using microsatellite and gene locus markers in Chinook salmon (Oncorhynchus tshawytscha) populations

Using different classes of genetic markers can provide insight into the role of selection, as well as a broader context for identifying population differentiation. We used nine microsatellite loci and polymorphisms at eight gene loci (major histocompatibility complex (MHC) classes I and II, growth hormones 1 and 2, transferrin, and immunoglobin heavy-chain) to determine population structure in six coastal populations (Vancouver Island, VI) and five interior populations (Fraser River, FR) of Chinook salmon (Oncorhynchus tshawytscha) in British Columbia, Canada. FSTand [Formula: see text] values for specific VI gene loci were significantly higher than those for the FR and VI microsatellite loci or the FR gene loci. Pairwise microsatellite FSTvalues were correlated with geographic distance across regions, but not using the gene locus marker data. Neighbor-joining cluster analyses showed one VI population as particularly divergent based on the gene locus data, while the VI and FR microsatellite locus and the FR gene locus analyses yielded no anomalous population divergence. The VI MHC class II marker FSTvalues were exceptionally high, indicative of probable directional selection acting on MHC class II. Our results are consistent with local adaptation in Chinook salmon, but the nature of the local adaptation likely differs among regions.

Use of sequence data from rainbow trout and Atlantic salmon for SNP detection in Pacific salmon

Single nucleotide polymorphisms (SNPs) are a class of genetic markers that are well suited to a broad range of research and management applications. Although advances in genotyping chemistries and analysis methods continue to increase the potential advantages of using SNPs to address molecular ecological questions, the scarcity of available DNA sequence data for most species has limited marker development. As the number and diversity of species being targeted for large-scale sequencing has increased, so has the potential for using sequence from sister taxa for marker development in species of interest. We evaluated the use of Oncorhynchus mykiss and Salmo salar sequence data to identify SNPs in three other species (Oncorhynchus tshawytscha, Oncorhynchus nerka and Oncorhynchus keta). Primers designed based on O. mykiss and S. salar alignments were more successful than primers designed based on Oncorhynchus-only alignments for sequencing target species, presumably due to the much larger number of potential targets available from the former alignments and possibly greater sequence conservation in those targets. In sequencing approximately 89 kb we observed a frequency of 4.30 x 10(-3) SNPs per base pair. Approximately half (53/101) of the subsequently designed validation assays resulted in high-throughput SNP genotyping markers. We speculate that this relatively low conversion rate may reflect the duplicated nature of the salmon genome. Our results suggest that a large number of SNPs could be developed for Pacific salmon using sequence data from other species. While the costs of DNA sequencing are still significant, these must be compared to the costs of using other marker classes for a given application.

Genetic Differences Between Two Wild and One Farmed Population of Atlantic Salmon (Salmo salar) Revealed by Three Classes of Genetic Markers

Mjelnerad, I. B., Refseth, U. H., Karlsen, E., Balstad, T., Jakobsen, K. S. and Hindar, K. 1997. Genetic differences between two wild and one farmed population of Atlantic salmon (Salmo salar) revealed by three classes of genetic markers. Hereditas 127: 239-248. Lund, Sweden. ISSN 0018-0661. Received April 7, 1997. Accepted August 21, 1997 Genetic diversity within and between two wild and one farmed population of Atlantic salmon was estimated by 12 variable enzyme loci, three single locus- and one multilocus DNA minisatellite probe. The farmed salmon were fifth-generation fish from one of the principal commercial strains in Norway and the wild salmon were from the rivers Numedalslagen and Tana, Norway. All three classes of markers detected significant differentiation between the populations, with the farmed population being genetically most divergent. The farmed fish showed less genetic variability than the wild populations, as all techniques revealed a lower (14 %-45 %) number of variable bands/alleles in this group. However, only multilocus DNA fingerprinting detected a significantly lower level of heterozygosity within the farmed population. Estimates of average heterozygosity within populations were almost identical for single locus and multilocus minisatellites (0.558 and 0.548, respectively), which were more than three times higher than for polymorphic allozymes (0.162). Estimates of interpopulation genetic differentiation, however, gave highly concordant results between the allozymes and minisatellites (Fst range: 0.106-0.135). Our results show that fifth generation farmed Atlantic salmon differ significantly from wild salmon in loci others than those chosen for selection in the breeding program. The study also suggests that the choice of genetic markers for studies of Atlantic salmon depends on the aim of the study (within- versus between-population variability).

Genetic structure and affinity among eight ethnic populations of Eastern India: based on 22 polymorphic DNA loci.

The nature and extent of genetic variation at 22 polymorphic DNA loci, belonging to three distinct classes, especially, 12 STR loci (D3S1358, vWA, FGA, D5S818, D13S317, D7S820, D8S1179, D21S11, D18S51, HPRTB, F13B, LPL), four VNTR loci (D1S7, D4S139, D5S110, D17S79), and six coding loci (HLDQA1, LDLR, GYPA, HBGG, D7S8, GC) were investigated among eight population groups of West Bengal and Manipur regions of India. Of these, two groups from West Bengal belong to Caucasoid and six (one in WB and five in Manipur) belong to Mongoloid stock. Both STR and the expressed loci show wide diversity among the eight populations. For example, Manipur Muslims show differences in allele frequency when compared to four other regional populations. Similarly, Garo, one of the Mongoloid populations of West Bengal, differ in allele frequency from their counterparts in the Manipur region. Departure from Hardy-Weinberg expectations was observed at certain loci in a few populations (e.g., D21S1137 in Kayastha and Brahmin, HUM F13B in Meitei). Heterozygosity values were higher for Caucasoid than Mongoloid groups. The overall gene differentiation (GST) for STR loci is higher (5.3%) than for those at the expressed region (4.6%). The clustering pattern of the eight populations differs with respect to different classes of genetic markers used. The dendrograms based on six coding loci (HLDQA1, LDLR, GYPA, HBGG, D7S8, GC) differs from those based on STR and VNTR markers. Caucasoid and Mongoloid groups form different clusters and Manipur Muslims are distinct from others. The clustering pattern corresponded with the spatial and ethnic affiliations of the populations. Using different classes of DNA loci at the coding and noncoding region will help to better understand the influence of population structure variables on the genetic structure of populations.

Comprehensive analysis of Alu-associated diversity on the human sex chromosomes

A comprehensive analysis of the human sex chromosomes was undertaken to assess Alu-associated human genomic diversity and to identify novel Alu insertion polymorphisms for the study of human evolution. Three hundred forty-five recently integrated Alu elements from eight different Alu subfamilies were identified on the X and Y chromosomes, 225 of which were selected and analyzed by polymerase chain reaction (PCR). From a total of 225 elements analyzed, 16 were found to be polymorphic on the X chromosome and one on the Y chromosome. In line with previous research using other classes of genetic markers, our results indicate reduced Alu-associated insertion polymorphism on the human sex chromosomes, presumably reflective of the reduced recombination rates and lower effective population sizes on the sex chromosomes. The Alu insertion polymorphisms identified in this study should prove useful for the study of human population genetics.

Beta-globin-like gene cluster haplotypes in hemoglobinopathies.

The pioneering work of Kan and Dozy () revealed by restriction endonuclease mapping a genetic variation in an HpaI recognition site about 5000 nucleotides from the 3′ end of the β-globin gene. Instead of a normal 7.6-kb fragment containing the β-globin gene, 7.0- and 13.0-kb variants were detected and were found in African Americans, Asians, and Caucasians. The 13.0-kb variant (HpaI+) was frequently associated with the sickle hemoglobin (Hb) mutation. Kan and Dozy () predicted that polymorphisms in a restriction enzyme site could be considered a new class of genetic marker and may offer a new approach to linkage analysis and anthropological studies. Based on limited data (), they reported that linkage to the wild-type HpaI-positive site was characteristic of West Africans while an HpaI-negative site typified East Africans. This finding did not show definitively that the mutation had occurred in two different chromosomal backgrounds, because a secondary mutation at the HpaI site could have postdated the sickle mutation.

Molecular status of the dusky Canada goose (Branta canadensis occidentalis): A genetic assessment of a translocation effort

Until recently, the dusky Canada goose (Branta canadensis occidentalis) was managedas one breeding population from the CopperRiver Delta (CRD), Alaska. Population numberson the CRD have declined precipitously over thelast three decades, due in part to changes inhabitat. In 1981, a pair of Canada geese,presumably B.c. occidentalis, wasreported nesting on Middleton Island (MID), inthe Gulf of Alaska. Numbers of Canada geese onthe island increased in the decade subsequentto a translocation of geese from CRD to MID,but it is unclear whether the increase isattributable to the translocation effort. Weused genetic data derived from three classes ofgenetic markers to clarify relationships ofCanada geese breeding in south-coastal Alaska. Geese were sampled from 5 populations: CRD,MID, Anchorage (ANC), Admiralty Island (ADM) insoutheastern Alaska, and Green Island (GRN) inPrince William Sound (PWS). Mitochondrial DNAanalyses demonstrate Canada geese from MID arenearly monomorphic for a unique haplotype fixedon GRN but not found in CRD or any otherbreeding population. Furthermore, nuclearmarkers consistently cluster MID with GRN tothe exclusion of CRD. We suggest the currentpopulation on MID is not derived from birdstranslocated from CRD, but rather that MID wasmost likely colonised by birds inhabiting otherisland habitats within the PWS. Furthermore,since geese from the CRD share mtDNA haplotypeswith geese from other breeding locales, theyapparently share recent common ancestry and/orgene flow with populations representing othersubspecies. Our genetic data raise questionsabout the validity of current management unitsof Canada geese.