Improvement of metric traits through specific genetic loci

1967 ◽  
Vol 9 (3) ◽  
pp. 349-358 ◽  
Author(s):  
Charles Smith
Keyword(s):  
Genetic Variation ◽  
Carcass Traits ◽  
Indirect Selection ◽  
Farm Animals ◽  
Sampling Errors ◽  
Economic Traits ◽  
Genetic Loci ◽  
Additive Genetic Variation ◽  
Metric Traits ◽  
Rate Of Improvement

Known genetic loci that affect metric traits may be useful in livestock improvement. Their value depends on the proportion (R) of the total additive genetic variation due to the known loci relative to the heritability of the trait concerned and on the form of selection practised. When normal selection is effective, further information on known loci can add only a little to the rate of improvement. But if normal selection is not very effective, as for characters of low heritability, or if indirect selection on relatives must be used (as for sex-limited or carcass traits) then known loci may add significantly to the rate of improvement possible.Sampling errors in the estimated effects and in the proportion (R) may cause selection effort to be misdirected and may even lead to losses rather than gains in improvement. Such errors are most likely to occur when the heritability of the character is low.Reports on several loci with large effects in the various farm species have been summarised, but the evidence is often inconsistent and contradictory. At present, there appear to be no loci that could be used with confidence in the improvement of economic traits in farm animals.

Genetic parameters of carcass quality in Down cross sheep

1968 ◽  
Vol 10 (2) ◽  
pp. 183-191 ◽  
Author(s):  
J. C. Bowman ◽  
J. E. Marshall ◽  
J. S. Broadbent
Keyword(s):  
Genetic Variation ◽  
Genetic Parameters ◽  
Carcass Traits ◽  
Genetic Correlations ◽  
Carcass Quality ◽  
Correction Factors ◽  
Muscle Area ◽  
Eye Muscle ◽  
Additive Genetic Variation ◽  
Commercial Value

This report gives an account of the paternal half-sib analysis of carcass quality, based on commercial joint dissection, on Down cross sheep collected in the four years 1962–65 inclusive. It also includes a discussion of the multiplicative correction factors used, and the phenotypic and genetic correlations between all the traits, estimated from the pooled within-farm, within-year analysis. It shows that there is very little genetic variation for many of the characters but that the percentage leg, percentage best end, age at slaughter and eye-muscle area have much additive genetic variation remaining for worthwhile response to be expected from selection. These three carcass traits are also the most important characters in determining the commercial value and saleability of lamb. From the results obtained it is argued that there is still much genetic variation for fat development in sheep.

scholarly journals Pleiotropy and multilocus polymorphisms.

Genetics ◽  
1992 ◽  
Vol 130 (1) ◽  
pp. 223-227
Author(s):  
A Gimelfarb
Keyword(s):  
Genetic Variation ◽  
Linkage Disequilibrium ◽  
Stabilizing Selection ◽  
Additive Genetic Variation ◽  
Very High

Abstract It is demonstrated that systems of two pleiotropically related characters controlled by additive diallelic loci can maintain under Gaussian stabilizing selection a stable polymorphism in more than two loci. It is also shown that such systems may have multiple stable polymorphic equilibria. Stabilizing selection generates negative linkage disequilibrium, as a result of which the equilibrium phenotypic variances are quite low, even though the level of allelic polymorphisms can be very high. Consequently, large amounts of additive genetic variation can be hidden in populations at equilibrium under stabilizing selection on pleiotropically related characters.

Genetic variation in an orchardgrass population promises successful direct or indirect selection of superior drought tolerant genotypes

2018 ◽  
Vol 137 (6) ◽  
pp. 928-935 ◽  
Author(s):  
Mozhgan Abtahi ◽  
Mohammad Mahdi Majidi ◽  
Behnam Hoseini ◽  
Aghafakhr Mirlohi ◽  
Bahram Araghi ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Indirect Selection ◽  
Drought Tolerant ◽  
Selection Of

Unravelling the genetic loci for growth and carcass traits in Chinese Bamaxiang pigs based on a 1.4 million SNP array

2018 ◽  
Vol 136 (1) ◽  
pp. 3-14 ◽  
Author(s):  
Huanfa Gong ◽  
Shijun Xiao ◽  
Wanbo Li ◽  
Tao Huang ◽  
Xiaochang Huang ◽  
...  
Keyword(s):  
Carcass Traits ◽  
Snp Array ◽  
Genetic Loci

Estimating the heritability of butterfat production

1961 ◽  
Vol 57 (3) ◽  
pp. 289-294 ◽  
Author(s):  
S. R. Searle
Keyword(s):  
Genetic Variation ◽  
New Zealand ◽  
Dairy Cows ◽  
Total Variance ◽  
Additive Effects ◽  
Narrow Sense ◽  
Sampling Errors ◽  
Gene Effects ◽  
Additive Gene Effects ◽  
Additive Gene

Part of the variation among butterfat yields in dairy cows arises from genetic differences among the animals. The proportion which this bears to the total variance is known as heritability. In the ‘narrow’ sense it is defined (Lush, 1940), as the proportion of the total variance that is due to additive gene effects; the ‘broad’ sense definition includes genetic variation arising from non-additive gene effects as well as that due to additive effects. Since related animals have a proportion of their genes in common the covariance among their production records can be used for estimating genetic variation and hence heritability. This paper discusses three groups of related animals most frequently used for this purpose, twins, daughter-dam pairs and paternal half-sibs, and presents the results of analysing production records of artificially bred heifers in New Zealand, including evidence of the magnitude of the sampling errors of the heritability estimates.

scholarly journals Characterizing the oligogenic architecture of plant growth phenotypes informs genomic selection approaches in a common wheat population

BMC Genomics ◽  
2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Noah DeWitt ◽  
Mohammed Guedira ◽  
Edwin Lauer ◽  
J. Paul Murphy ◽  
David Marshall ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Plant Growth ◽  
Genomic Selection ◽  
Plant Height ◽  
Prediction Models ◽  
Growth Traits ◽  
Heading Date ◽  
Additive Genetic Variation ◽  
Moderate Effect ◽  
Over Time

Abstract Background Genetic variation in growth over the course of the season is a major source of grain yield variation in wheat, and for this reason variants controlling heading date and plant height are among the best-characterized in wheat genetics. While the major variants for these traits have been cloned, the importance of these variants in contributing to genetic variation for plant growth over time is not fully understood. Here we develop a biparental population segregating for major variants for both plant height and flowering time to characterize the genetic architecture of the traits and identify additional novel QTL. Results We find that additive genetic variation for both traits is almost entirely associated with major and moderate-effect QTL, including four novel heading date QTL and four novel plant height QTL. FT2 and Vrn-A3 are proposed as candidate genes underlying QTL on chromosomes 3A and 7A, while Rht8 is mapped to chromosome 2D. These mapped QTL also underlie genetic variation in a longitudinal analysis of plant growth over time. The oligogenic architecture of these traits is further demonstrated by the superior trait prediction accuracy of QTL-based prediction models compared to polygenic genomic selection models. Conclusions In a population constructed from two modern wheat cultivars adapted to the southeast U.S., almost all additive genetic variation in plant growth traits is associated with known major variants or novel moderate-effect QTL. Major transgressive segregation was observed in this population despite the similar plant height and heading date characters of the parental lines. This segregation is being driven primarily by a small number of mapped QTL, instead of by many small-effect, undetected QTL. As most breeding populations in the southeast U.S. segregate for known QTL for these traits, genetic variation in plant height and heading date in these populations likely emerges from similar combinations of major and moderate effect QTL. We can make more accurate and cost-effective prediction models by targeted genotyping of key SNPs.

scholarly journals Mhc polymorphisms fail to explain the heritability of phytohaemagglutinin-induced skin swelling in a wild passerine

2009 ◽  
Vol 5 (6) ◽  
pp. 784-787 ◽  
Author(s):  
Camille Bonneaud ◽  
Janet S. Sinsheimer ◽  
Murielle Richard ◽  
Olivier Chastel ◽  
Gabriele Sorci
Keyword(s):  
Genetic Variation ◽  
Immune Responses ◽  
Environmental Effects ◽  
Natural Populations ◽  
Wild Populations ◽  
Genetic Determinants ◽  
House Sparrows ◽  
Additive Genetic Variation ◽  
Significant Heritability ◽  
Mhc Polymorphisms

Genetic estimates of the variability of immune responses are rarely examined in natural populations because of confounding environmental effects. As a result, and because of the difficulty of pinpointing the genetic determinants of immunity, no study has to our knowledge examined the contribution of specific genes to the heritability of an immune response in wild populations. We cross-fostered nestling house sparrows to disrupt the association between genetic and environmental effects and determine the heritability of the response to a classic immunological test, the phytohaemagglutinin (PHA)-induced skin swelling. We detected significant heritability estimates of the response to PHA, of body mass and tarsus length when nestlings were 5 and 10 days old. Variation at Mhc genes, however, did not explain a significant portion of the genetic variation of nestling swelling to PHA. Our results suggest that while PHA-induced swelling is influenced by the nest of origin, the importance of additive genetic variation relative to non-additive genetic variation and the genetic factors that influence the former in wild populations still need to be identified for this trait.

scholarly journals Shared additive genetic variation for alcohol dependence among subjects of African and European ancestry

2017 ◽  
Vol 24 (1) ◽  
pp. 132-144 ◽  
Author(s):  
Leslie A. Brick ◽  
Matthew C. Keller ◽  
Valerie S. Knopik ◽  
John E. McGeary ◽  
Rohan H.C. Palmer
Keyword(s):  
Genetic Variation ◽  
Alcohol Dependence ◽  
European Ancestry ◽  
Additive Genetic Variation
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