scholarly journals Selection for an Invariant Character, Vibrissa Number, in the House Mouse II. Limits to Variability

1960 ◽  
Vol 13 (1) ◽  
pp. 48 ◽  
Author(s):  
AS Fraser ◽  
BM Kindred
Keyword(s):  
House Mouse ◽  
Phenotypic Variation ◽  
Reproductive Fitness ◽  
Selection Experiment ◽  
Frequency Distributions ◽  
Selection For ◽  
Seven Generations

A selection experiment for vibrissa number in tabby mice has been extended for 13 generations. Progress of selection for the first seven generations has already been reported. The results of the next six generations of selection are given and the whole experiment is considered with regard to (1) the shapes of the frequency distributions for the three genotypes (+, Ta+, and Ta�) for succeeding generations; (2) limits to phenotypic variation, i.e. canalization mechanisms; and (3) reproductive fitness.

scholarly journals Selection for an invariant Character, Vibrissa Number, in the House Mouse III. Correlated Responses

1962 ◽  
Vol 15 (1) ◽  
pp. 188 ◽  
Author(s):  
AS Fraser ◽  
BM Kindred
Keyword(s):  
House Mouse ◽  
Low Frequency ◽  
Mutant Mice ◽  
Selection Experiment ◽  
Correlated Responses ◽  
Very Low Frequency ◽  
Selection For

Selection for increased and decreased total number of secondary vibrissae has been practised on the mutant mice of a stock in which the tabby gene is segregating. Five separate groups of vibrissae contribute to the total number and differences were found in the response of individual groups of vibrissae to selection. These differences occur both in the main selection experiment and in subsidiary experi-ments based on rare non-tabby mice with abnormal scores which occur with very low frequency in ordinary mouse stocks.

scholarly journals Continued artificial selection for running endurance in rats is associated with improved lung function

2009 ◽  
Vol 106 (6) ◽  
pp. 1810-1818 ◽  
Author(s):  
Scott D. Kirkton ◽  
Richard A. Howlett ◽  
Norberto C. Gonzalez ◽  
Patrick G. Giuliano ◽  
Steven L. Britton ◽  
...  
Keyword(s):  
Body Size ◽  
Lung Volume ◽  
Maximal Oxygen Consumption ◽  
Endurance Capacity ◽  
Endurance Running ◽  
Body Frame ◽  
Cardiopulmonary Function ◽  
Muscle Adaptations ◽  
Selection For ◽  
Seven Generations

Previous studies found that selection for endurance running in untrained rats produced distinct high (HCR) and low (LCR) capacity runners. Furthermore, despite weighing 14% less, 7th generation HCR rats achieved the same absolute maximal oxygen consumption (V̇o2max) as LCR due to muscle adaptations that improved oxygen extraction and use. However, there were no differences in cardiopulmonary function after seven generations of selection. If selection for increased endurance capacity continued, we hypothesized that due to the serial nature of oxygen delivery enhanced cardiopulmonary function would be required. In the present study, generation 15 rats selected for high and low endurance running capacity showed differences in pulmonary function. HCR, now 25% lighter than LCR, reached a 12% higher absolute V̇o2max than LCR, P < 0.05 (49% higher V̇o2max/kg). Despite the 25% difference in body size, both lung volume (at 20 cmH2O airway pressure) and exercise diffusing capacity were similar in HCR and LCR. Lung volume of LCR lay on published mammalian allometrical relationships while that of HCR lay above that line. Alveolar ventilation at V̇o2max was 30% higher, P < 0.05 (78% higher, per kg), arterial Pco2 was 4.5 mmHg (17%) lower, P < 0.05, while total pulmonary vascular resistance was (insignificantly) 5% lower (30% lower, per kg) in HCR. The smaller mass of HCR animals was due mostly to a smaller body frame rather than to a lower fat mass. These findings show that by generation 15, lung size in smaller HCR rats is not reduced in concert with their smaller body size, but has remained similar to that of LCR, supporting the hypothesis that continued selection for increased endurance capacity requires relatively larger lungs, supporting greater ventilation, gas exchange, and pulmonary vascular conductance.

RESPONSE TO SELECTION FOR BODY WEIGHT OR FEED EFFICIENCY IN MICE TESTED ON CORN, RYE AND WHEAT DIETS

1986 ◽  
Vol 66 (2) ◽  
pp. 389-397
Author(s):  
R. I. McKAY ◽  
R. J. PARKER ◽  
W. GUENTER
Keyword(s):  
Body Weight ◽  
Feed Efficiency ◽  
Mass Selection ◽  
Response To Selection ◽  
Initial Weight ◽  
Commercial Diet ◽  
Final Weight ◽  
Dc Line ◽  
Selection For ◽  
Seven Generations

Mass selection for adjusted feed efficiency (AFE, g gain/g feed) and adjusted body weight (ABW, g) of male mice was practiced for seven generations on each of three diets: corn, rye and wheat. The three experimental diets, fed between 21 and 35 d, were isocaloric (approximately 16.5 MJ GE kg−1) and isonitrogenous (CP approximately 13%). A common commerical diet (PC) was fed at all other times. With each diet two control lines, randomly mated, were tested on either the experimental diets (DC) or a commercial diet (PC). Selection was based upon linear adjustment to a common initial weight (10 g) for either final weight (ABW) or feed efficiency (AFE) measured between 21 and 35 d of age. Response was determined as a deviation from the appropriate DC line. All animals were placed in specially designed individual cages during the test period. Half-sib estimates of heritability in the PC line were 0.13(± 0.11) for ABW and 0.19(± 0.10) for AFE. Half-sib estimates pooled across lines and diets were 0.16(± 0.07) for ABW and 0.28(± 0.07) for AFE. Realized heritabilities for ABW were 0.24(± 0.06), 0.06(± 0.07) and 0.14(± 0.06) for the corn, rye and wheat diets, respectively. Response to selection for AFE was poor with the highest heritability obtained on the wheat diet (h2 = 0.13 ± 0.02). Key words: Selection, mice, body weight, feed efficiency, diets

Effect of selection for increased litter size on ovulation rate and embryo survival in sheep

1990 ◽  
Vol 1990 ◽  
pp. 32-32 ◽  
Author(s):  
J.P. Hanrahan
Keyword(s):  
Litter Size ◽  
Ovulation Rate ◽  
Control Line ◽  
Selection Experiment ◽  
Embryo Survival ◽  
Relative Contribution ◽  
Variation Data ◽  
Component Traits ◽  
Selection For ◽  
The Impact

Variation in litter size in sheep is essentially attributable to variation in ovulation rate and embryo survival. Genetic variation in litter size, both among and within breeds, is largely attributable to variation in ovulation rate. While there is evidence for genetic differences among breeds in embryo survival the contribution of this component to within breed variation appears to be minor (Hanrahan, 1982). The impact of selection based on litter size on its component traits should reflect the relative contribution of these components to within breed variation. Data from two lines of Galway sheep, a Control line and one selected for increased prolificacy (Hanrahan and Timon, 1978), have been used to provide evidence on this point.Details relating to the selection experiment which provided the data for the present study are in Hanrahan (1984). Briefly a flock of Galway sheep was assembled from industry sources (both pedigree and non-pedigree) between 1963 and 1965.

scholarly journals Response to selection for increased pupa weight in Tribolium castaneum as related to population structure

1977 ◽  
Vol 30 (3) ◽  
pp. 237-246 ◽  
Author(s):  
Alan J. Katz ◽  
Franklin D. Enfield
Keyword(s):  
Random Mating ◽  
Selection Response ◽  
Response To Selection ◽  
Short Term ◽  
Selection Systems ◽  
Line Selection ◽  
Selection For ◽  
Seven Generations ◽  
Generation Period ◽  
Term Response

SUMMARYThe effectiveness of selection for increased pupa weight in Tribolium was compared for three different selection systems. In all three systems the same number of breeding individuals was used each generation. Population L was a large random mating population with 24 males and 48 females selected each generation. The C4 and C8 populations were each divided into 6 subpopulations (lines) consisting of 4 males and 8 fem ales. Each of the three populations was replicated. In C4, selection for pupa weight was within lines for three generations, followed by a generation of among-line selection when the best two out of six lines were selected. These lines were then crossed to produce 6 new subpopulations, and the cycle was repeated. The C8 population was handled in exactly the same manner except that seven generations of selection within lines were practised before each generation of among-line selection. Selection response for the 42-generation period was significantly greater in the L population than in either subdivided population. No consistent differences among the selection systems were apparent when evaluating short-term response for the first 12 generations of the experiment. The results were interpreted as indicating that the influence of multiple-peak epistasis was not of major importance for this trait in determining ultimate response to selection when starting from a base population of previously unselected lines and utilizing a within- and among-line selection regime.

Selection for high or low backfat depth in Coopworth sheep: juvenile traits

1997 ◽  
Vol 65 (1) ◽  
pp. 93-103 ◽  
Author(s):  
C. A. Morris ◽  
J. C. McEwan ◽  
P. F. Fennessy ◽  
W. E. Bain ◽  
G. J. Greer ◽  
...  
Keyword(s):  
Animal Model ◽  
Maximum Likelihood ◽  
Random Sample ◽  
Live Weight ◽  
Control Line ◽  
Selection Experiment ◽  
Initial Screening ◽  
Genetic And Phenotypic Correlations ◽  
Selection For ◽  
Subsequent Selection

AbstractA selection experiment was established in Coopworth sheep in 1981 to breed for increased or reduced ultrasonic backfat depth (scan C). Foundation females came from four flocks recorded for scan C and live weight, with weight-adjusted scan C data within flock being used for initial screening and subsequent selection. Three groups of animals per source flock, comprising proportionally the fattest 0·12, a random sample, and the leanest 0·12, were used to establish the F, control and L lines, respectively. Ewe flock numbers from 1981 to 1992 averaged 51 per line. Foundation rams were selected in the same manner from four different farms (two sources each in 1981 and 1982) to provide F line (proportionally the fattest 0·04), control line and L line (leanest 0·04) rams for use in 1981 and 1982, with four mated per line per year. Thereafter homebred rams were selected, with 41 or 42 homebred rams being used per line until 1992. Average generation intervals were 2·13 years and annual inbreeding rates per line 0·004. Bivariate heritability estimates for log scan C and log live weight, and a univariate estimate for log scan C using restricted maximum likelihood with an animal model, were 0·28, 0·22 and 0·38, respectively (all with s.e. 0·03). There was a suggestion of lower heritabilities in the L line for log scan C after adjustment for live weight. Realized heritabilities in the F and L lines were 0·34 (s.e. 0·07) and 0·26 (s.e. 0·03), respectively. Deviations of back-transformed weight-adjusted scan C in the last 2 years ofF and L data analysed (1991 and 1992 birth years) from the control flocks were 2·08 and −0·85 mm, which corresponded to responses of +2·50 and −1·03 phenotypic standard deviations, respectively. In addition there were relatively large responses in live weight taken at scanning, with F and L lines averaging 34·0 and 40·2 kg, compared with 38·0 kg for controls in the 1991 and 1992 birth years. The genetic and phenotypic correlations between log scan C and log live weight at scanning were 0·16 (s.e. 0·07) and 0·46 (s.e. 0·01) respectively.

Selection for an Invariant Character—‘Vibrissa Number’—in the House Mouse

Nature ◽  
1958 ◽  
Vol 181 (4614) ◽  
pp. 1018-1019 ◽  
Author(s):  
R. B. DUN ◽  
A. S. FRASER
Keyword(s):  
House Mouse ◽  
Selection For
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