scholarly journals Long-term selection for protein amount over 70 generations in mice

1998 ◽  
Vol 72 (2) ◽  
pp. 93-109 ◽  
Author(s):  
LUTZ BÜNGER ◽  
ULLA RENNE ◽  
GERHARD DIETL ◽  
SIEGFRIED KUHLA
Keyword(s):  
Body Weight ◽  
Selection Response ◽  
Direct Selection ◽  
Control Line ◽  
Phenotypic Variance ◽  
Effective Population ◽  
Term Selection ◽  
General Importance ◽  
Selection For

Based on the outbred mouse strain Fzt: Du, which has been obtained by systematic crossing of four inbred and four outbred lines, a long-term selection experiment was carried out for total protein amount (PA) in the carcass, starting in 1975. An unselected control line (CO) was kept under the same management but without continuous protein analysis. The protein amount of male carcasses at 42 days of age (P42) increased from 2·9 g in generation 0 to 5·2 g at generation 70, representing 97% of a theoretical selection limit. The total selection response amounts to 2·3 g, which is about 80% above the initial value and corresponds to 9σp or 12σA . The estimated realized heritability of protein amount decreased from 0·56 to 0·03 at generation 70, which was due to an increase in phenotypic variance from 0·065 to 0·24 g2 and a reduction in genetic variance from 0·04 to 0·01 g2. Half the selection response was obtained after about 18 to 23 generations, a half-life of 0·25 to 0·3 Ne. The maximum selection response was 0·094 g/generation and the response was 0·01 g/generation at generation 70. The measurements of body weights at 0, 10, 21, 42 and 63 days throughout the experiment showed a strong correlated effect for all weights. The PA mice are one of the heaviest lines of mice ever reported, and do not differ significantly in their body composition from control mice at 42 days. The direct selection response was due primarily to increased general growth. Body weight and protein amount are phenotypically and genetically highly correlated (rp=0·82, rA≈1); however, selection for body weight led to fatter animals, whereas selection for protein opposed increased fatness (at least until selection age). This may be of general importance in animal breeding. The comparatively high selection response in this experiment seems due to the heterogeneity of the base population, the relatively high effective population size, and the duration of the experiment.

CARCASS COMPOSITION OF MICE AFTER LONG-TERM SELECTION FOR LARGE SIX-WEEK BODY WEIGHT OR LONG SIX-WEEK TAIL LENGTH

1985 ◽  
Vol 65 (1) ◽  
pp. 239-242 ◽  
Author(s):  
R. I. McKAY ◽  
A. D. GRAHAM ◽  
R. J. PARKER
Keyword(s):  
Body Weight ◽  
Key Words ◽  
Tail Length ◽  
Fat Deposition ◽  
Carcass Composition ◽  
Control Line ◽  
Selected Lines ◽  
Term Selection ◽  
Selection For

Carcass analysis of mice selected for large 6-wk body weight (BW6) or long 6-wk tail length (TL6) is reported. There was no evidence of excessive fat deposition in the selected lines when compared to a randomly bred control line. Key words: Mice, carcass composition, selection, fat

scholarly journals LONG-TERM SELECTION RESPONSE FOR 12-DAY LITTER WEIGHT IN MICE

Genetics ◽  
1972 ◽  
Vol 72 (1) ◽  
pp. 129-142
Author(s):  
E J Eisen
Keyword(s):  
Body Weight ◽  
Genetic Correlation ◽  
Half Life ◽  
Selection Process ◽  
Selection Response ◽  
Exponential Model ◽  
Correlated Response ◽  
Term Selection ◽  
Litter Weight

ABSTRACT Long-term selection for increased 12-day litter weight in two replicate lines (W2, W3) of mice resulted in an apparent selection limit at about 17 generations. Quadratic polynomial and exponential models were fitted to the data in order to estimate the plateaued response and half-life of the selection process. Using the polynomial results, the half-life estimates were 4.5 and 8.6 generations for W2 and W3, respectively. The plateaued responses were 5.1 and 5.8 g which, when expressed in phenotypic standard deviation units, became 1.1 and 1.3. The exponential model provides similar estimates. A negative association between 12-day litter weight and fitness was not considered to be an adequate explanation for the plateau since there was no decrease in fertility of the selected lines. Evidence that exhaustion of genetic variability was not the cause of the plateau came from the immediate response to reverse selection. It was proposed that the plateau may be due to a negative genetic correlation between direct and maternal genetic effects, which would be expected to occur after many generations of selection. There were positive correlated responses in both replicates for adult body weight, which was in agreement with the positive genetic correlation between preweaning and postweaning body weight. The expected positive correlated response for number born was realized in only one of the replicates.

scholarly journals Optimum selection intensities in artificial selection programmes: an experimental evaluation

1977 ◽  
Vol 30 (2) ◽  
pp. 115-119 ◽  
Author(s):  
R. Frankham
Keyword(s):  
Experimental Evaluation ◽  
Selection Intensity ◽  
Effective Population ◽  
Term Selection ◽  
Optimum Selection ◽  
Selection For ◽  
Selection Intensities ◽  
Selection Of ◽  
Better Than

SUMMARYAn experimental evaluation of Robertson's (1970) theory concerning optimum intensities of selection for selection of varying durations has been carried out using published results from a long term selection study in Drosophila. Agreement of predicted rankings of treatments with expectations was excellent for low values of t/T (generations/total number scored) but poor for larger values of t/T. This was due to the 20% selection intensity treatments responding worse than expected and the 40% treatments relatively better than expected. Several possible reasons for the discrepancies exist but the most likely explanation is considered to be the greater reduction in effective population size due to selection in treatments with more intense selection.

scholarly journals Effects of leptin administration on long-term selected fat mice

1997 ◽  
Vol 69 (3) ◽  
pp. 215-225 ◽  
Author(s):  
LUTZ BÜNGER ◽  
WILLIAM G. HILL
Keyword(s):  
Matter Content ◽  
Control Line ◽  
Dry Matter Content ◽  
Genetic Changes ◽  
Term Selection ◽  
Wide Range ◽  
Selection For ◽  
Phosphate Buffered Saline

To assess the role of genetic changes in sensitivity to leptin hormone in contributing to responses to long-term selection for fatness, leptin was administered to a long-term fat selected (F) and a control line (C) of mice. These lines differ almost three fold in their percentage of fat (fat%) at about 15 weeks of age. Treated (T) animals received twice-daily intraperitoneal injections of 5 mg/kg leptin from 91 to 105 days of age; untreated (U) animals received equivolume injections of phosphate-buffered saline. Treated compared with untreated animals in both lines had significantly (P<0·05) lower mean body weight, food intake and fatness at the end of test (fat%: CT 3%, CU 7·4%, FT 14·9%, FU21·1%). The differences in response between the lines [(CT−CU)−(FT−FU)] were all non-significant (P>0·05), however. There was a very wide range of fatness (estimated from dry matter content) among FT animals (3–29%), much higher than in FU (15–31%), CT (0·7–6·4%) and CU (2–15%) animals. While sensitivity to leptin remains in the fat line, response appears to vary among animals at the dose level used.

scholarly journals A complex multi-locus, multi-allelic genetic architecture underlying the long-term selection-response in the Virginia body weight line of chickens

2017 ◽  
Author(s):  
Yanjun Zan ◽  
Zheya Sheng ◽  
Lars Rönnegård ◽  
Christa F. Honaker ◽  
Paul B. Siegel ◽  
...  
Keyword(s):  
Body Weight ◽  
Additive Genetic Variance ◽  
Natural Populations ◽  
Selection Response ◽  
Multiple Alleles ◽  
Term Selection ◽  
Selection Responses ◽  
Genome Wide ◽  
Genetic Mechanisms

AbstractThe ability of a population to adapt to changes in their living conditions, whether in nature or captivity, often depends on polymorphisms in multiple genes across the genome. In-depth studies of such polygenic adaptations are difficult in natural populations, but can be approached using the resources provided by artificial selection experiments. Here, we dissect the genetic mechanisms involved in long-term selection responses of the Virginia chicken lines, populations that after 40 generations of divergent selection for 56-day body weight display a nine-fold difference in the selected trait. In the F15 generation of an intercross between the divergent lines, 20 loci explained more than 60% of the additive genetic variance for the selected trait. We focused particularly on seven major QTL and found that only two fine-mapped to single, bi-allelic loci; the other five contained linked loci, multiple alleles or were epistatic. This detailed dissection of the polygenic adaptations in the Virginia lines provides a deeper understanding of genome-wide mechanisms involved in the long-term selection responses. The results illustrate that long-term selection responses, even from populations with a limited genetic diversity, can be polygenic and influenced by a range of genetic mechanisms.

scholarly journals Identification of Genes Targeted in South African Merino and Afrino Sheep Populations Under Long-Term Selection for Reproduction and Body Weight

2020 ◽  
Author(s):  
Margaretha Snyman ◽  
Sunika Süllwald ◽  
Willem Olivier ◽  
Carina Visser
Keyword(s):  
Body Weight ◽  
South African ◽  
Reproductive Performance ◽  
Genome Wide Association Study ◽  
Growth Traits ◽  
Reproductive Traits ◽  
Term Selection ◽  
A Genome ◽  
Selection For

Abstract Background: Reproductive performance and body weight are of the utmost economic importance in determining the efficiency of sheep production. Simultaneous selection for increased reproductive performance and early growth traits is a common strategy in many flocks, but ambiguous results regarding the relationship between reproduction and body weight have been reported. The objective of this study was to perform a genome-wide association study (GWAS) in two South African Merino flocks and an Afrino sheep flock that were selected for both reproduction and body weight over decades. The GWAS aimed to identify SNPs associated with genes affecting the traits number of lambs born (NLB), number of lambs weaned (NLW), total weight of lamb weaned (TWW) and body weight (BW) and thus to ascertain which genes were targeted through directional selection.Results: In the GWAS, 16 SNP markers associated with reproductive traits were identified among the three populations, while 15 SNPs were associated with body weight. These SNPs were linked respectively to 26 and 21 documented genes in the sheep genome. Most of these genes were previously associated in literature with reproduction related, as well as with growth related traits in various farm animal species. This study, supported by results from previous studies performed on sheep and cattle, identified the following genes that warrant further investigation as to their functions and processes relating to growth and reproduction in sheep: MAP7D1, TRAPPC3, THRAP3, TRMP8, SPP2, HDAC9, ZFHX3, SIX6, C14orf39, TAF4B, TRSP1 EYA2, RBMS3, STL38L, BSPH1, LIG1, CABP5 and ELSPBP1. Conclusions: Long-term selection in the flocks for both body weight and reproductive traits, and especially on the composite trait TWW, have favoured genes with pleiotropic effects influencing both groups of traits. SNPs associated with these pleiotropic genes were detected in the association analyses for the various traits.

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