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L Gomez-Raya

Publications and source records attributed to L Gomez-Raya.

16 recordsLinked to original sources
PubMed2004

A linkage map of Atlantic salmon (Salmo salar) reveals an uncommonly large difference in recombination rate between the sexes.

A genetic linkage map of the Atlantic salmon (Salmo salar) was constructed, using 54 microsatellites and 473 amplified fragment length polymorphism (AFLP) markers. The mapping population consisted of two full-sib families within one paternal half-sib family from the Norwegian breeding population. A mapping strategy was developed that facilitated the construction of separate male and female maps, while retaining all the information contributed by the dominant AFLP markers. By using this strategy, we were able to map a significant number of the AFLP markers for which all informative offspring had two heterozygous parents; these markers then served as bridges between the male and female maps. The female map spanned 901 cM and had 33 linkage groups, while the male spanned 103 cM and had 31 linkage groups. Twenty-five linkage groups were common between the two maps. The construction of the genetic map revealed a large difference in recombination rate between females and males. The ratio of female recombination rate vs. male recombination rate was 8.26, the highest ratio reported for any vertebrate. This map constitutes the first linkage map of Atlantic salmon, one of the most important aquaculture species worldwide.

Animals↗
PubMed2003

Reallocation of body resources in lactating mice highly selected for litter size.

The present study investigated differences in the allocation patterns of body stores in lactating female mice from a line selected for high litter size at birth (S-line, average litter size of 20) and dams from a nonselected control line (C-line, average litter size of 10). Body weight, litter size, litter weight, and absolute and relative lipid and protein mass were measured at peak lactation (2 wk in lactation) and at weaning (3 wk in lactation). Body size in S-line females has been increased as a correlated effect of selection for high litter size at birth, allowing for larger litters and higher absolute milk production. However, these dams produce larger litters relative to their own body weight. At peak lactation, lipid and protein percentage did not differ between lines. At weaning, S-line females had a higher protein percentage (P < 0.001) and lower lipid percentage (P < 0.05) than C-line females. Apparently, S-line females produce more offspring but at a greater cost to their own metabolism. This process was insufficient to supply the offspring with adequate resources, resulting in reduced (P < 0.0001) pup development and increased (P < 0.0001) preweaning mortality rates.

Animals↗
PubMed2002

A genome scan for quantitative trait loci affecting milk production in Norwegian dairy cattle.

An autosomal genome scan for quantitative trait loci (QTL) affecting milk production traits was carried out on the Norwegian Dairy Cattle population. Six half-sibling families with a total of 285 sons organized according to a granddaughter design were analyzed by a multiple marker regression method. Suggestive QTL for one or several of the five milk traits (milk yield, protein percentage, protein yield, fat percentage and fat yield) were detected on chromosomes 3, 5, 6, 11, 13, 18 and 20. Among these results, the findings on chromosomes 3, 6, and 20 are highly supported by literature. The most convincing result was found close to marker FBN9 on chromosome 6, where a QTL was detected with alleles that cause a marked reduction in both protein and fat percentages and an increase in milk yield. The results for fat and protein percentage were highly significant even after accounting for multiple testing across the genome. Using bootstrapping, a 95% confidence interval for the position of the QTL for the percentage traits on chromosome 6 was estimated to 16 cM.

Animals↗
PubMed2001

Quantitative trait loci affecting clinical mastitis and somatic cell count in dairy cattle.

Norway has a field recording system for dairy cattle that includes recording of all veterinary treatments on an individual animal basis from 1978 onwards. Application of these data in a genome search for quantitative trait loci (QTL) verified genome-wise significant QTL affecting clinical mastitis on Chromosome (Chr) 6. Additional putative QTL for clinical mastitis were localized to Chrs. 3, 4, 14, and 27. The comprehensive field recording system includes information on somatic cell count as well. This trait is often used in selection against mastitis when direct information on clinical mastitis is not available. The absence of common QTL positions for the two traits in our study indicates that the use of somatic cell count data in QTL studies aimed for reducing the incidence of mastitis should be carefully evaluated.

Animals↗
PubMed2001

Biased estimation of the recombination fraction using half-sib families and informative offspring.

A maximum-likelihood method to estimate the recombination fraction and its sampling variance using informative and noninformative half-sib offspring is derived. Estimates of the recombination fraction are biased up to 20 cM when noninformative offspring are discarded. In certain scenarios, the sampling variance can be increased or reduced up to fivefold due to the bias in estimating the recombination fraction and the LOD score can be reduced up to 5 units when discarding noninformative offspring. Comparison of the estimates of recombination fraction, map distance, and LOD score when constructing a genetic map with 251 two-point linkage analyses and six families of Norwegian cattle was carried out to evaluate the implications of discarding noninformative offspring in practical situations. The average discrepancies in absolute value (average difference when using and neglecting noninformative offspring) were 0.0146, 1.64 cM, and 2.61 for the recombination fraction, map distance, and the LOD score, respectively. A method for simultaneous estimation of allele frequencies in the dam population and a transmission disequilibrium parameter is proposed. This method might account for the bias in estimating allele frequencies in the dam population when the half-sib offspring is selected for production traits.

Alleles↗
PubMed2000

A primary screen of the bovine genome for quantitative trait loci affecting twinning rate.

An autosomal genome scan for quantitative trait loci (QTL) affecting twinning rate was carried out in the Norwegian Cattle population. Suggestive QTL were detected on Chromosomes (Chr) 5, 7, 12, and 23. Among these, the QTL positions on both Chr 5 and Chr 23 are strongly supported by literature in the field. Our results also confirm previous mapping of a QTL for twinning to Chr 7, but definitely suggest a different location of the QTL on this chromosome. The most convincing QTL peak was observed for a region in the middle part of Chr 5 close to the insulin-like growth factor 1 (IGF1) gene. Since IGF1 plays an important role in the regulation of folliculogenesis, a mutation search was performed by sequencing more than 3.5 kb of the gene in actual families. The sequencing revealed three polymorphisms in noncoding regions of the gene that will be important in fine structure mapping and characterization of the QTL.

Animals↗
PubMed2000

Consensus and comprehensive linkage maps of bovine chromosome 7.

The objective of this project was to integrate the currently available linkage maps for bovine chromosome 7 (BTA7) by combining data sets from eight research groups. A total of 54 unique markers were typed in eight pedigrees. Multilocus linkage analysis with CRI-MAP produced a bovine chromosome 7 consensus framework map of 27 loci ordered with odds greater than 1000:1. Furthermore, we present a bovine chromosome 7 comprehensive map integrating 54 loci. The locus order is in general agreement with the recently published linkage maps except for one discrepancy. The order of loci BM9289, BMS713, and ILSTS001 was reversed in the consensus framework map relative to the published USDA-MARC bovine chromosome 7 linkage map.

Animals↗
PubMed1999

High-resolution gametic map of the sheep callipyge region: linkage heterogeneity among rams detected by sperm typing.

The callipyge locus (CLPG) causing muscular hypertrophy in domestic sheep has previously been mapped to the distal part of ovine chromosome 18. In this study, an accurate multipoint linkage map consisting of six microsatellite markers in this chromosomal region was constructed based on the analysis of 1145 single sperm cells. The best supported order of markers was OARHH47-ILSTS54-MCM38-CSSM18-IDVGA30-BM S1561. The log odds against the second most likely order, which has a reversal of the closely linked markers CSSM18 and IDVGA30, was 5.026. Sperm typing can be used to examine a large number of meioses in single individuals, and therefore, was exploited to study individual variability of recombination rate in rams of different callipyge genotypes. The results revealed statistically significant linkage heterogeneity among rams (P < 0.05) for marker interval OARHH47-CSSM18, with individual recombination fractions varying from 0.209 to 0.357.

Animals↗
PubMed1999

Bovine chromosome 4 workshop: consensus and comprehensive linkage maps.

The report of the bovine chromosome 4 (BTA4) workshop is presented. Six laboratories contributed a total of 30,168 informative meioses from 62 loci. Twenty-two loci were typed by at least two independent laboratories and were used to construct a consensus linkage map of BTA4. The remaining 40 loci were subsequently incorporated into a comprehensive map. The sex-averaged consensus map covered 131.4 cM. The female map was 124.3 cM in length, while the male map was 134.3 cM. The comprehensive sex-averaged map spanned 141.6 cM. The length of the female and male comprehensive maps were 123.1 cM and 156.4 cM, respectively. Average genetic distance between loci was 6 and 2.3 cM for the consensus and comprehensive linkage maps, respectively.

Animals↗
PubMed1999

Two-stage selection strategies utilizing marker-quantitative trait locus information and individual performance.

Short- and long-term response to marker-assisted selection in two stages was studied using a stochastic simulation of a closed nucleus herd for beef production. First-stage selection was carried out within families based on information at a fully additive quantitative trait locus (QTL). Second-stage selection strategies were based on 1) individual phenotype, 2) individual phenotype precorrected for QTL, 3) a selection index incorporating phenotype and QTL information, 4) a standard animal model BLUP, and 5) a selection index incorporating marker-QTL information and standard animal model BLUP on records precorrected for QTL. All strategies were efficient in moving the favorable allele at the QTL to fixation, but they differed in the time to reach fixation. Mass selection was less efficient in changing allele frequencies than BLUP. Discounted accumulated response, accounting for the time response was realized and inflation rate, was proposed to rank strategies and to elude the conflict between short- and long-term response in marker-assisted selection. Discounted accumulated response at a time horizon of 20 yr for alternative two-stage selection strategies was compared with conventional BLUP carried out in second stage only. Within-family selection increased discounted accumulated response by more than 11% using Strategy 4 and by up to 12% using Strategy 5 at an inflation rate of 2%. The percentage increase in response was less for highly heritable traits and when the proportion of additive variance explained by the QTL was small. Strategy 5 gave larger response with reduced inbreeding. This strategy also resulted in the lowest cost-benefit ratio, requiring less genotyping per unit of response. Cost-benefit ratio for discounted genotyping and for discounted in vitro production of embryos for traits with low heritability was two to four times that for traits with high heritability. The use of first-stage selection slightly increased the level of inbreeding for both mass (Strategy 1) and BLUP selection (Strategies 4 and 5).

Animals↗
PubMed1997

Mapping of bovine FcgammaR (FCGR) genes by sperm typing allows extended use of human map information.

Polymorphic sites within the bovine FcgammaRI (FCGR1), FcgammaRII (FCGR2), and FcgammaRIII (FCGR3) genes were used for proximal mapping of these genes to bovine Chromosome (Chr) 3 (BTA3) with paternal half-sib families from Norwegian Cattle. A fine-structure genetic map of the region was obtained by the analysis of 288 sperm cells from three bulls that were heterozygous for the loci included in the study. No recombinants were observed between FCGR2 and FCGR3 (242 sperm cells). Considering FCGR2 and FCGR3 as a single locus, a three-point linkage analysis for [FCGR2/FCGR3], FCGR1, and INRA003 was carried out. The best-supported order of the loci was found to be INRA003-FCGR1-[FCGR2/FCGR3]. Map distances in a two-point linkage analysis were 10.3 cM between [FCGR2/FCGR3] and FCGR1, and 25.5 cM between FCGR1 and INRA003, respectively. This linkage mapping of the bovine FCGR gene family resembles the human situation where all FCGR genes are located at Chr 1 (HSA1), at position q21-q24. Moreover, the results locate the evolutionary breakpoint between HSA1q and BTA3 within the human 1q24 region.

Alleles↗
PubMed1995

The role of melanocyte-stimulating hormone (MSH) receptor in bovine coat color determination.

The melanocyte-stimulating hormone (MSH) receptor has a major function in the regulation of black (eumelanin) versus red (phaeomelanin) pigment synthesis within melanocytes. We report three alleles of the MSH-receptor gene found in cattle. A point mutation in the dominant allele ED gives black coat color, whereas a frameshift mutation, producing a prematurely terminated receptor, in homozygous e/e animals, produces red coat color. The wild-type allele E+ produces a variety of colors, reflecting the possibilities for regulating the normal receptor. Microsatellite analysis, RFLP studies, and coat color information were used to localize the MSH-receptor to bovine Chromosome (Chr) 18.

Alleles↗
PubMed1995

Associations between casein haplotypes and milk yield traits.

The genotyping of 13 sires and 250 of their sons for casein polymorphisms revealed 10 different haplotypes for Norwegian Cattle. Associations between haplotypes and yields of protein, milk, and fat were studied using a granddaughter design. Three subsets of data containing families with haplotypes 1, 5, and 10 were analyzed independently and denoted by analyses 1, 5, and 10, respectively. In addition, all sire families of all haplotypes were pooled and analyzed in analysis T. No associations were found between haplotypes and traits for milk yield in analyses 1, 10, and T. However, the null hypothesis of an equal effect within sire of bulls was rejected in analysis 5 for yields of protein and milk. The increase in protein yield associated with haplotype 5 ranged from 2.52 to 14.58 kg (from .09 to .51 phenotypic standard deviations). These results may indicate the presence of at least one quantitative trait locus in the region of the casein genes that affects protein yield of Norwegian Cattle. The findings were confirmed with a new analysis of two large sire families segregating haplotype 5 (analysis 5N).

Animals↗
PubMed1993

Within-family selection at an otherwise unselected locus in dairy cattle.

Identification of allelic variants with economic importance is feasible via molecular genetic techniques. This information can be used to increase the frequency of favourable alleles in dairy cattle. The effect of selection on the genotype within families in the early stages of life is examined. Three different strategies are considered: (1) random mating of bull sires with bull dams and with cows, with embryo selection of young bulls and all cows; (2) random mating of bull sires with bull dams, with embryo selection of young bulls only; (3) minimizing or avoiding matings between homozygotes for the unfavourable allele, with embryo selection of young bulls. Selection strategies assume the use of reproductive technologies such as embryo transfer to produce large family sizes for within-family selection to be practiced. All the three strategies increase the frequency of the favourable allele rapidly. Strategy 1 gives the fastest increase in the frequency of the favourable allele. The increase in the frequency of the favourable allele is slower under random mating (strategy 2) than under a negative assortative mating (strategy 3). This is a novel example of increased selection response with negative assortative mating.

Alleles↗