Description of bovine major histocompatibility complex class IIa haplotypes using parthenogenetic embryo-derived cells.

In this study, we report an approach to characterize individual BoLA haplotypes using cells from parthenogenetic bovine embryos derived from slaughterhouse ovaries. Eight of the 15 parthenogenetic embryos so obtained had not undergone meiotic recombination on the BoLA region and were suitable to describe BoLA haplotypes. Detailed analysis of the BoLA class IIa region identified seven different class IIa haplotypes, including six not previously described and two new alleles of BoLA-DQA and one BoLA-DQB. Our method provided reliable sources of homozygous DNA to describe BoLA haplotypes.

A high-resolution radiation hybrid map of the river buffalo major histocompatibility complex and comparison with BoLA.

The major histocompatibility complex (MHC) in mammals codes for antigen-presenting proteins. For this reason, the MHC is of great importance for immune function and animal health. Previous studies revealed this gene-dense and polymorphic region in river buffalo to be on the short arm of chromosome 2, which is homologous to cattle chromosome 23. Using cattle-derived STS markers and a river buffalo radiation hybrid (RH) panel (BBURH5000 ), we generated a high-resolution RH map of the river buffalo MHC region. The buffalo MHC RH map (cR5000 ) was aligned with the cattle MHC RH map (cR12000 ) to compare gene order. The buffalo MHC had similar organization to the cattle MHC, with class II genes distributed in two segments, class IIa and class IIb. Class IIa was closely associated with the class I and class III regions, and class IIb was a separate cluster. A total of 53 markers were distributed into two linkage groups based on a two-point LOD score threshold of ≥8. The first linkage group included 32 markers from class IIa, class I and class III. The second linkage group included 21 markers from class IIb. Bacterial artificial chromosome clones for seven loci were mapped by fluorescence in situ hybridization on metaphase chromosomes using single- and double-color hybridizations. The order of cytogenetically mapped markers in the region corroborated the physical order of markers obtained from the RH map and served as anchor points to align and orient the linkage groups.

Distributional characterizations and testing for differences of relatedness and inbreeding of a subpopulation of American Hereford bulls.

Beta distributions are characterized by two determining parameters and a parameter space from 0 to 1, and may be useful for examining population genetic parameters such as the relationship or inbreeding coefficients. Often subpopulations exist within breeds that are congregated around particular lineages of cattle or ancestors that breeders value. These subpopulations are more related to each other than to the majority of other animals; they may have higher inbreeding as well. Value may be added to these subpopulations because of their relatedness with important or renowned ancestors. The objectives of this work were to compare the relatedness and inbreeding of a group of 26 modern bulls from a subpopulation of the American Hereford breed relative to 1) 30 males with the most descendants present in the pedigree, 2) 15 renowned American Hereford bulls considered important individuals in the breed's history, and 3) 19 prominent subpopulation male ancestors. Conformance of the mean relationship coefficients of the bulls with the three groups and the mean inbreeding coefficient with all pedigree animals to beta distributions was assessed by 1) visually determining the parameters of the beta distributions based on the entire pedigree, 2) testing the mean relationship coefficient or inbreeding coefficient of the group of subpopulation bulls for its positional inclusion in those distributions, and 3) bootstrap sampling methodology. The mean relationship coefficients of the 26 Trask bulls with the 30 bulls with the most descendants, the 15 renowned ancestors, and the 19 Trask male ancestors were 0.15, 0.132, and 0.208, respectively. Testing of these means in beta distributions indicated that the group of 26 Trask bulls were no more related to the three groups of bulls than all of the animals in the pedigree (0.06 < P < 0.25). Bootstrap sampling indicated that the 26 bulls were more related to the three groups of male ancestors than the remainder of the animals in the pedigree (P < 0.0001). The mean inbreeding coefficient of the 26 bulls (0.13) did not differ from the overall inbreeding coefficient (0.056) when tested using a beta distribution; however, bootstrap sampling indicated otherwise (P < 0.0001). Results may indicate the inadequacy of visually parameterizing a beta distribution. Quantification of pedigree relatedness of a group of animals to key ancestors, especially with no DNA available, may add value to that group and individuals.

Fragile sites in domestic animal chromosomes: molecular insights and challenges.

Fragile sites are intriguing cytogenetic phenomena that have been extensively investigated in human and laboratory animal chromosomes over the past 40 years, but domestic animal species have been studied sporadically. Interest in the field has been recently renewed as increasing numbers of fragile site regions are cloned and characterized at the molecular level. Despite much effort, mechanisms by which specific DNA sequence confers fragility to a chromosome region remain unclear. Recent advancements in sequencing and mapping of domestic animal genomes provide tools for molecular characterization of fragile sites in animal chromosomes. Future comparative efforts may contribute insight into both the mechanisms that underlie chromosome fragility, and forces that drive rearrangements observed throughout evolution, and somatic changes that can result in disease or impair fertility.

First radiation hybrid map of the river buffalo X chromosome (BBUX) and comparison with BTAX.

We report the first radiation hybrid map of the river buffalo X chromosome generated from a recently constructed river buffalo (Bubalus bubalis) whole-genome radiation hybrid panel (BBURH(5000)). This map contains a total of 33 cattle-derived markers, including 10 genes, four ESTs and 19 microsatellites. The markers are distributed in two linkage groups: LG1 contains eight markers spanning 125.6 cR, and LG2 contains 25 markers spanning 366.3 cR. LG1 contains six markers in common with bovine sequence assembly build 3.1. With the exception of BMS2152, the order of these markers on our BBUX map is shuffled when compared to the cow X chromosome (Bos taurus; BTAX). From LG2, two markers (AMELX and BL22) map to a more distal portion of BTAX compared to BBUX. In addition, two pairs of LG2 markers exhibit inversions compared to BTAX (ILSTS017 and ATRX; XBM38 and PPEF1). Alternatively, when compared to the most recent bovine RH map (Bov-Gen 3000rads), BL1098 and BMS2227 from LG1 as well as PLS3 and BMS1820 from LG2 showed inverted positions on the BBUX map. These discrepancies in buffalo and cattle maps may reflect evolutionary divergence of the chromosomes or mapping errors in one of the two species. Although the set of mapped markers does not cover the entire X chromosome, this map is a starting point for the construction of a high-resolution map, which is necessary for characterization of small rearrangements that might have occurred between the Bubalus bubalis and Bos taurus X chromosomes.

Mapping MHC genes in river buffalo.

The major histocompatibility complex (MHC) contains a set of genes necessary for antigen presentation in the immune system. This gene dense and polymorphic region of the mammalian genome is of considerable interest due to the role of MHC genes in immune function and animal health. Previous cytogenetic studies have indicated that the MHC in river buffalo resides on the short arm of chromosome 2 (BBU2). A 5000-rad radiation hybrid mapping panel was recently generated to enable construction of a whole genome map of river buffalo. To this end, the aims of this project were to elucidate the general organization of the MHC on BBU2, and to compare gene order within this region to the MHC in cattle. PCR primers were selected from the bovine gene map and used with the BBURH5000 panel to map a set of ten MHC class II genes in river buffalo. Analysis indicates that these genes fall into two linkage groups, consistent with organization of the MHC in cattle. This comparison of buffalo and bovine MHC gene order provides the first insight into the organization of the MHC on river buffalo chromosome 2.

Report of a chimeric origin of transposable elements in a bovine-coding gene.

Despite the wide distribution of transposable elements (TEs) in mammalian genomes, part of their evolutionary significance remains to be discovered. Today there is a substantial amount of evidence showing that TEs are involved in the generation of new exons in different species. In the present study, we searched 22,805 genes and reported the occurrence of TE-cassettes in coding sequences of 542 cow genes using the RepeatMasker program. Despite the significant number (542) of genes with TE insertions in exons only 14 (2.6%) of them were translated into protein, which we characterized as chimeric genes. From these chimeric genes, only the FAST kinase domains 3 (FASTKD3) gene, present on chromosome BTA 20, is a functional gene and showed evidence of the exaptation event. The genome sequence analysis showed that the last exon coding sequence of bovine FASTKD3 is approximately 85% similar to the ART2A retrotransposon sequence. In addition, comparison among FASTKD3 proteins shows that the last exon is very divergent from those of Homo sapiens, Pan troglodytes and Canis familiares. We suggest that the gene structure of bovine FASTKD3 gene could have originated by several ectopic recombinations between TE copies. Additionally, the absence of TE sequences in all other species analyzed suggests that the TE insertion is clade-specific, mainly in the ruminant lineage.

A radiation hybrid map of river buffalo (Bubalus bubalis) chromosome 1 (BBU1).

The largest chromosome in the river buffalo karyotype, BBU1, is a submetacentric chromosome with reported homology between BBU1q and bovine chromosome 1 and between BBU1p and BTA27. We present the first radiation hybrid map of this chromosome containing 69 cattle derived markers including 48 coding genes, 17 microsatellites and four ESTs distributed in two linkage groups spanning a total length of 1330.1 cR(5000). The RH map was constructed based on analysis of a recently developed river buffalo-hamster whole genome radiation hybrid (BBURH(5000)) panel. The retention frequency of individual markers across the panel ranged from 17.8 to 52.2%. With few exceptions, the order of markers within linkage groups is identical to the order established for corresponding cattle RH maps. The BBU1 map provides a starting point for comparison of gene order rearrangements between river buffalo chromosome 1 and its bovine homologs.

Association of udder traits with single nucleotide polymorphisms in crossbred Bos indicus-Bos taurus cows.

The size, support, and health of udders limit the productive life of beef cows, especially those with background, because, in general, such cows have a reputation for problems with udders. Genomic association studies of bovine udder traits have been conducted in dairy cattle and recently in Continental European beef breeds but not in cows with background. The objective of this study was to determine associations of SNP and udder support scores, teat length, and teat diameter in half (Nellore), half (Angus) cows. Udders of cows ( = 295) born from 2003 to 2007 were evaluated for udder support and teat length and diameter ( = 1,746 records) from 2005 through 2014. These included a subjective score representing udder support (values of 1 indicated poorly supported, pendulous udders and values of 9 indicated very well-supported udders) and lengths and diameters of individual teats in the 4 udder quarters as well as the average. Cows were in full-sibling or half-sibling families. Residuals for each trait were produced from repeated records models with cow age category nested within birth year of cows. Those residuals were averaged to become the dependent variables for genomewide association analyses. Regression analyses of those dependent variables included genotypic values as explanatory variables for 34,980 SNP from a commercially available array and included the genomic relationship matrix. Fifteen SNP loci on BTA 5 were associated (false discovery rate controlled at 0.05) with udder support score. One of those was also detected as associated with average teat diameter. Three of those 15 SNP were located within genes, including one each in (), (), and (). These are notable for their functional role in some aspect of mammary gland formation or health. Other candidate genes for these traits in the vicinity of the SNP loci include () and (). Because these were detected in Nellore-Angus crossbred cows, which typically have very well-formed udders with excellent support across their productive lives, similar efforts in other breeds should be completed, because that may facilitate further refinement of genomic regions responsible for variation in udder traits important in multiple breeds.

Crossbred steer temperament as yearlings and whole genome association of steer temperament as yearlings and calf temperament post-weaning.

cattle often have the reputation for a poor or dangerous temperament. Identification of genomic regions that associate with temperament of such cattle may be useful for genetic improvement strategies. The objectives of this study were to evaluate subjective temperament scores (1 to 9; higher scores indicated more unfavorable temperament) for aggressiveness, nervousness, flightiness, gregariousness, and overall temperament of one-half steers in feedlot conditions at 1 yr of age and compare those scores of those steers when evaluated approximately 1 mo postweaning, and conduct whole genome association analyses using SNP markers and the temperament traits of those steers at 1 yr of age and for temperament traits of all calves at weaning. Contemporary groups ( < 0.001) were steers born in the same year and season, and fed in the same feedlot pen. Aggressiveness of steers at 1 yr of age was not associated with aggressiveness at weaning (linear regression coefficient did not differ from 0; = 0.96), but regressions of all other yearling scores of steers on the scores at weaning were positive (coefficients ranged from 0.26 ± 0.04 to 0.32 ± 0.04; < 0.001). Estimates of Pearson correlation coefficients (using unadjusted values and residual values) of the different traits measured at 1 yr of age were large ( > 0.63; < 0.008) except for aggressiveness with nervousness, flightiness, or gregariousness, which did not differ from 0 ( > 0.1). Five SNP on BTA 1, 24, and 29 had suggestive associations (0.17 < [adjusted for FDR] < 0.24) with aggressiveness, nervousness, or flightiness at evaluation postweaning and 13 SNP on 11 chromosomes had suggestive associations (0.07 < [adjusted for FDR] < 0.24) with aggressiveness, nervousness, flightiness, or overall temperament score of steers at 1 yr of age. Genes close to these loci with roles in neural systems of various organisms included synaptotagmin 4 (BTA 24), FAT atypical cadhedrin 3 (BTA 29), tubulin tyrosine ligase-like 1 (BTA 5), spermatogenesis associated 17 (BTA 16), stanniocalcin 2 (BTA 20), and GABA receptor γ 3 (BTA 21).

Factors affecting therapeutic concentration of topical aminocaproic acid in traumatic hyphema.

Epsilon-aminocaproic acid (EACA) decreases rebleeding in traumatic hyphema through antifibrinolytic activity. Therapeutic levels were achieved in aqueous humor of rabbits after topical application. Aqueous humor EACA levels were significantly higher after pretreatment with 0.5% proparacaine. Use of EACA (60%) in a carboxypolymethylene (CPM) vehicle (0.5%, 1%, 2%, 3%, and 4%) was examined. Aqueous humors levels at 4 hours ranged from 6.18-20.42 micrograms/ml. The 2% and 3% formulas achieved the highest concentrations in aqueous. Use of EACA (15%, 30%, 40%, and 60%) in 4% CPM was also studied. At 2 and 4 hours after treatment, the 30% EACA solution most effectively achieved therapeutic levels. Velcro closure devices were attached to the rabbit's eyelids, and 200 microliters of 30% EACA in 2% CPM was administered. After 3 hours the patched eyes had a mean aqueous EACA level of 60.09 micrograms/ml compared with 8.97 micrograms/ml in unpatched eyes. When dose size was studied in patched eyes, 200-microliters doses achieved aqueous levels of 60.09 micrograms/ml, and 100-microliters doses resulted in levels of 10.40 micrograms/ml. Since epithelial toxicity was observed in eyes that had been patched, the optimum topical regimen appeared to be 200 microliters of 30% EACA in 2% CPM every 6 hours in unpatched eyes.

Genetic evaluation of aspects of temperament in Nellore-Angus calves.

The objective of this work was to estimate heritability of each of 5 subjectively measured aspects of temperament of cattle and the genetic correlations of pairs of those traits. From 2003 to 2013, Nellore-Angus F2 and F3 calves (n = 1,816) were evaluated for aspects of temperament at an average 259 d of age, which was approximately 2 mo after weaning. Calves were separated from a group and subjectively scored from 1 (calm, good temperament) to 9 (wild, poor temperament) for aggressiveness (willingness to hit an evaluator), nervousness, flightiness, gregariousness (willingness to separate from the group), and a distinct overall score by 4 evaluators. Data were analyzed using threshold and linear models with additive genetic random effects. Two-trait animal models (nonthreshold) included the additive genetic covariance for pairs of traits and were used to estimate additive genetic correlations. Contemporary groups (n = 104) represented calves penned together for evaluation on given evaluation days. Heifers had greater (worse) means for all traits than steers (P < 0.05). The regression of score on age in days was included in final models for flightiness (P = 0.05; -0.006 ± 0.003) and gregariousness (P = 0.025; -0.007 ± 0.003). Estimates of heritability were large (0.51, 0.4, 0.45, 0.49, and 0.47 for aggressiveness, nervousness, flightiness, gregariousness, and overall temperament, respectively; SE = 0.07 for each). The ability to use this methodology to distinctly separate different aspects of calf temperament appeared to be limited, as estimates of additive genetic correlations were near unity for all pairs of traits; estimates of phenotypic correlation ranged from 0.88 ± 0.01 to 0.99 ± 0.002 for pairs of traits. Distinct subsequent analyses indicated a significant negative relationship of 4 of the various temperament scores with weight at weaning (regression coefficients ranged from -0.008 ± 0.002 for nervousness, flightiness, and gregariousness to -0.003 ± 0.002 for aggressiveness). In subsequent analyses, the regression of temperament trait on sequence of evaluation within a pen was highly significant and solutions ranged from 0.05 ± 0.007 for aggressiveness to 0.08 ± 0.007 for all other traits. The apparent large additive genetic variance for any one of these traits may be useful in identification of genes responsible for differences in cattle temperament.

Gene expression in the arcuate nucleus of heifers is affected by controlled intake of high- and low-concentrate diets.

It was hypothesized that a high-concentrate diet fed during early calfhood alters the expression of genes within the arcuate nucleus that subserve reproductive competence. Beef heifers (n = 12) were weaned at approximately 3 mo of age, and after acclimation, were allocated randomly to 1 of 2 nutritional groups: 1) High Concentrate/High Gain (HC/HG), a high concentrate diet fed to promote a gain of 0.91 kg/d; or 2) High Forage/Low Gain (HF/LG), a forage-based diet fed to promote a gain of 0.45 kg/d. Experimental diets were fed under controlled intake for 91 d. At the end of 91 d, heifers were slaughtered by humane procedures, blood samples were collected, brains were removed, liver weights were determined, and rumen fluid was collected for VFA analyses. Tissue blocks containing the hypothalamus were dissected from the brains, frozen, and cut using a cryostat, and frozen sections were mounted on slides. Tissue from the arcuate nucleus (ARC) was dissected from sections for mRNA extraction. Microarray analysis was used to assess genome-wide transcription in the ARC using a 60-mer oligonucleotide 44K bovine expression array. The ADG was greater (P < 0.001) in heifers fed the HC/HG diet than in heifers fed the HF/LG diet. At slaughter, mean propionate to acetate ratios in the ruminal fluid and liver weight as a percentage of BW were increased (P < 0.005) in HC/HG compared with HF/LG heifers. Mean serum concentrations of insulin (P < 0.05) and IGF-1 (P < 0.005) were greater, and leptin tended to be greater (P = 0.1) in HC/HG heifers compared with HF/LG heifers. Approximately 345 genes were observed to be differentially expressed in the HC/HG group with approximately two-thirds of the genes exhibiting increased expression in the HC/HG group. Genes exhibiting decreased expression in the HC/HG group included agouti-related protein and neuropeptide Y, products of which are known to regulate feed intake and energy expenditure. Functional annotation of enriched Gene Ontology terms indicates that a number of biological processes within the hypothalamus are affected by consumption of high-concentrate diets, including those related to control of feed intake, regulation of cellular metabolic processes, receptor and intracellular signaling, and neuronal communication. In summary, dietary treatments shown previously to accelerate the timing of pubertal onset in heifers increased ruminal propionate, promoted enhanced metabolic hormone secretion, and altered gene expression in the ARC.

Preliminary radiation hybrid map for river buffalo chromosome 6 and comparison to bovine chromosome 3.

We present the first radiation hybrid (RH) map of river buffalo (Bubalus bubalis) chromosome 6 (BBU6) developed with a recently constructed river buffalo whole-genome RH panel (BBURH(5000)). The preliminary map contains 33 cattle-derived markers, including 12 microsatellites, 19 coding genes and two ESTs, distributed across two linkage groups. Retention frequencies for markers ranged from 14.4% to 40.0%. Most of the marker orders within the linkage groups on BBU6 were consistent with the cattle genome sequence and RH maps. This preliminary RH map is the starting point for comparing gene order between river buffalo and cattle, presenting an opportunity for the examination of micro-rearrangements of these chromosomes. Also, resources for positional candidate cloning in river buffalo are enhanced.

Structure and chromosomal location of the bovine gene for the heart muscle isoform of cytochrome c oxidase subunit VIII.

We have isolated the bovine COX8H gene for the heart/muscle isoform of cytochrome c oxidase (COX) subunit VIII from a library of bovine genomic DNA cloned into lambda EMBL3. Primer extension assays on bovine heart mRNA mapped the 5' ends of COX8H transcripts to a CA dinucleotide 62-bp upstream from the ATG codon. The gene thus spans 1565-bp and comprises two exons and one large intron of 1227 bp. Exon 1 encodes the 5' untranslated region, a 24-amino acid presequence, and the first 13 amino acids of the mature COX VIII-H protein. Exon 2 encodes the remainder of the cDNA: amino acids 14 to 46 plus the 66-bp 3' untranslated region. The exon-intron boundaries matched the consensus splice junction sequences. Two protein polymorphisms were seen: an Ala/Val polymorphism at position -6 in the presequence and the previously noted Lys/Arg polymorphism at residue 7 of the mature protein. A TaqI polymorphism occurs in the intron. The COX8H gene was mapped by bovine x rodent somatic cell hybrid mapping panels to bovine (BTA) Chromosome (Chr) 25 with 100% concordancy. BTA 25 is conserved relative to the long arm of human (HSA) Chr 11, which contains COX8, the gene for the single human COX VIII subunit that is homologous to the liver isoform.

Alteration of Egr-1 mRNA during multistage carcinogenesis in mouse skin.

Immediate early genes, including fos, jun, and early growth response-1 (Egr-1), are induced during cellular response to changes in extracellular environment. These immediate early genes are believed to mediate processes of cell growth and differentiation. In particular, Egr-1 is induced during mitogenic stimulation of a variety of cell types, including fibroblasts, B cells, and epithelial cells. In the present study, we examined Egr-1 gene expression during multistage carcinogenesis in mouse skin. After a single topical treatment with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) to SENCAR mouse skin, Egr-1 mRNA was induced, and maximal induction was observed at 2 h in both epidermis and dermis. Induction of Egr-1 mRNA by TPA was inhibited by fluocinolone acetonide, a potent inhibitor of tumor promotion by TPA. Egr-1 mRNA was present in primary keratinocytes derived from adult SENCAR mice. The keratinocyte cultures were maintained in low Ca(2+) medium, and Egr-1 mRNA levels became significantly elevated after the cultures were switched to high Ca(2+) medium. Additionally, a large proportion of primary papillomas and carcinomas generated from SENCAR mice by standard initiation-promotion regimens exhibited elevated Egr-1 mRNA compared with normal epidermis. Taken together, these data suggest a possible role of Egr-1 during multistage carcinogenesis in mouse skin.

Analysis of aphidicolin-induced chromosome fragility in the domestic pig (Sus scrofa).

Aphidicolin (APC)-sensitive fragile sites were identified in chromosome preparations from peripheral lymphocyte cultures of 12 four-way crossbred pigs. A chi 2 analysis demonstrated that aphidicolin-induced breakage events and previously reported in vivo chromosome rearrangement events were not independent. Comparison of expected Poisson and negative binomial distributions to observed breakage patterns indicated that the negative binomial distribution provided a better fit to experimental data. The negative binomial distribution is consistent with a distribution of breakage rates, i.e., non-constant rates of breakage at chromosomal loci across the genome.

A high resolution GBG-banded karyotype of the Atlantic bottlenose dolphin, Tursiops truncatus: generation of an ideogram, and NOR localization by fluorescence in situ hybridization.

A high resolution karyotype was prepared using GBG-banded chromosomes from kidney epithelial cell lines of the Atlantic bottlenose dolphin, Tursiops truncatus. The karyotype was used to generate a banded ideogram of T. truncatus that will facilitate cytogenetic analyses essential for comparison of dolphin chromosomes with those of potentially related terrestrial vertebrates. Fluorescence in situ hybridization analysis of the karytype using a rodent (Geomys bursarius) 28S ribosomal DNA (rDNA) probe allowed localization of four nucleolar organizer (NOR) regions to the short arms of two chromosome pairs. FISH mapping, using DNA probes, is dependent on a pre-existing banded ideogram, and provides the means to initiate physical mapping of the dolphin genome.

Structure of the human gene (COX6A2) for the heart/muscle isoform of cytochrome c oxidase subunit VIa and its chromosomal location in humans, mice, and cattle.

We have mapped the gene for the heart/muscle isoform of cytochrome c oxidase (COX) subunit VIa in three mammalian species and isolated the human COX6AH gene (HGMW-approved symbol COX6A2). The bovine gene was mapped by somatic cell hybrid mapping panels to bovine chromosome BTA 25 with 94-95% concordance. The mouse gene (Cox6ah) was mapped using an interspecific backcross panel from the cross (C57BL/6J x Mus spretus)F1 x Mus spretus probed with the mouse COX VIa-H cDNA. Cox6ah was located on distal chromosome 7, between D7Mit8 and D7Mit13. From the regions of known gene conservation among these three species, we predicted that human COX6AH would be located on chromosome 16p. We hybridized a human x rodent mapping panel of somatic cell hybrids with the human cDNA to confirm this assignment. These data taken together indicated that the human COX6AH gene is located on the short arm of chromosome 16 and facilitated the isolation of the human gene from a chromosome 16-enriched library. The human COX6AH gene spans about 1 kb and contains three exons and two small introns. The sequences of the proximal 5' flanking regions of COX6AH genes are highly conserved between human, bovine, and rodent.

Development and initial characterization of a Bos taurus x B. gaurus interspecific hybrid backcross panel.

A panel of 40 Bos taurus x B. gaurus (gaur) interspecific hybrid backcross off spring was constructed for use as a tool in refining and improving the resolution of the bovine gene map. The gaur (2n = 58) is characterized karyotypically by a 2; 28 Robertsonian translocation with respect to the cattle karyotype (2n = 60). This translocation was used as a centromeric marker to directionally orient linkage maps of B. taurus (BTA) chromosomes 2 and 28. The initial linkage analysis of this panel consisted primarily of genes or DNA segments containing microsatellites previously placed on bovine maps. Two new markers, NRAMP1 and ACTA1, were added to the linkage maps on BTA2 and BTA28, respectively. Additionally, fibroblast cultures from fetal tissue of each offspring were analyzed cytogenetically at early passages. In all cases, the translocation chromosome was inherited in a balanced condition, and only one cell line possessed a chromosome abnormality. This aberrant line was determined to be trisomic, 61,XXX.