EFFECTS OF ANCESTRAL X IRRADIATION FOLLOWED BY RANDOM MATING ON BODY WEIGHT OF RATS

ABSTRACT Effects of nine generations of 450r per generation of ancestral spermatogonial X irradiation of inbred rats on body weight were examined. After six generations of random mating (avoiding inbreeding) following the termination of irradiation, descendants of irradiated males (R) were significantly lighter than their controls (C) at 3 and 6 weeks, but not at 10 weeks of age. However, differences in growth between R and C populations were small. Among-litter and within-litter variance estimates were generally larger in the R lines than in the C lines, suggesting that selection responses would be greater in R than in C lines. In conjunction with previous evidence—obtained during the irradiation phase of the experiment—this suggested that more rapid response to selection for 6-week body weight, in particular, might accrue in the R lines.

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The response to selection for body weight and egg weight in the fowl

10.31274/rtd-180814-4249 ◽

1964 ◽

Author(s):

Michael Franics Wogan Festing

Keyword(s):

Body Weight ◽

Response To Selection ◽

Egg Weight ◽

Selection For

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Simulation of Response to Selection for Body Weight in Rainbow Trout

Acta Agriculturae Scandinavica ◽

10.1080/00015128109435723 ◽

1981 ◽

Vol 31 (4) ◽

pp. 426-432 ◽

Cited By ~ 2

Author(s):

Sampo Sirkkomaa ◽

Ulf B. Lindström

Keyword(s):

Body Weight ◽

Rainbow Trout ◽

Response To Selection ◽

Selection For

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

Canadian Journal of Animal Science ◽

10.4141/cjas86-040 ◽

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

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Genetic variation in a line of mice selected to its limit for high body weight

Animal Science ◽

10.1017/s0003356100022856 ◽

1974 ◽

Vol 19 (3) ◽

pp. 273-289 ◽

Cited By ~ 5

Author(s):

W. K. Al-Murrani ◽

R. C. Roberts

Keyword(s):

Body Weight ◽

Genetic Variance ◽

Genetic Model ◽

Random Mating ◽

Inbred Lines ◽

High Body Weight ◽

High Body ◽

Lower Body Weight ◽

Recessive Genes ◽

Selection For

SUMMARYA line of mice, at its limit to selection for high body weight did not decline in performance over 11 generations of random mating, neither did it respond when selection was renewed. The experiment tested a method of improving body weight by a scheme which had earlier increased litter size under similar circumstances. The scheme was to derive partially inbred lines from the plateaued line, to select during inbreeding and, finally, to cross the best inbreds. Body weight was not increased, but the study allowed further examination of the residual genetic variance in the line.During inbreeding, the inbred lines became clearly differentiated in body weight, proving that loci controlling body weight had not become fixed. There was also a significant response to selection for a lower body weight during inbreeding. The pattern of results suggested the segregation of recessive genes, detrimental to high body weight but which selection had become inefficient at removing. A genetic model compatible with the results accommodated several such recessives, perhaps as many as 10, each with an effect of about two-thirds of a standard deviation (or some equivalent combination of gene number and effect), and at frequencies of around 0·2. Nevertheless, the total improvement in body weight to be gained by their elimination was only half a gram, or less than 2 %. Thus, substantial genetic effects can occur at individual loci despite trivially low heritabilities and negligible potential gains.

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EFFECT OF SELECTION ON HERITABILITY AND GENETIC CORRELATION OF TWO QUANTITATIVE TRAITS IN MICE

Canadian Journal of Genetics and Cytology ◽

10.1139/g74-066 ◽

1974 ◽

Vol 16 (3) ◽

pp. 599-609 ◽

Cited By ~ 9

Author(s):

T. K. Cheung ◽

R. J. Parker

Keyword(s):

Body Weight ◽

Genetic Correlation ◽

Quantitative Traits ◽

Random Mating ◽

Tail Length ◽

Control Group ◽

Mass Selection ◽

Initial Population ◽

Significant Difference ◽

Selection For

The effects of different intensities of single trait directional selection on the heritability and genetic correlation of two quantitative traits in random mating populations of mice were observed during 14 generations. The initial population was divided at random into five groups (A, B, C, D and E). Group A and Group B were under 30% and 60% mass selection for large 6-week body weight, respectively. Group C and Group D were under 30% and 60% mass selection for long 6-week tail length, respectively. Group E acted as control group with no selection applied. In all groups, the parent population consisted of 15 males and 30 females each generation, mated at random.Direct selection had no apparent effect on the heritability of either the trait under selection or the correlated trait over the 14 generations. Heritability of 6-wk tail length was higher than the heritability of 6-wk body weight. Estimates of heritability of 6-wk tail length ranged from 0.15 ± 0.22 to 0.68 ± 0.24, while estimates of heritability of 6-wk body weight ranged from 0.05 ± 0.17 to 0.33 ± 0.09. There was no significant difference among the estimates of genetic correlation between the two traits in the five selection groups. Estimates of realized genetic correlation between 6-wk body weight and 6-wk tail length seemed to indicate that more intense selection led to some decrease in genetic correlation between the two traits.

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

Genetics Research ◽

10.1017/s001667230001764x ◽

1977 ◽

Vol 30 (3) ◽

pp. 237-246 ◽

Cited By ~ 10

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.

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Selection for leukocyte counts in mice

Genetics Research ◽

10.1017/s0016672300010004 ◽

1966 ◽

Vol 8 (2) ◽

pp. 125-142 ◽

Cited By ~ 6

Author(s):

C. K. Chai

Keyword(s):

Body Weight ◽

Coat Color ◽

Leukocyte Count ◽

Individual Cell ◽

Cell Types ◽

Two Generations ◽

X Irradiation ◽

Leukocyte Counts ◽

Selection For ◽

The Individual

By directional selection for total leukocyte counts from a hybrid mouse stock we have gradually established two lines of mice, LLC (Low Leukocyte Count) and HLC (High Leukocyte Count), which differ both in total and in differential leukocyte counts. A randombred line (RLC) is also being concurrently maintained. Other variations between these lines of mice are in body weight, in the frequencies of coat color genes, reproductive performance, and resistance to X-irradiation. The LLC line was comparatively low in the latter two physiological parameters, and high in variation of body weight.Responses to selection for high and low leukocyte counts were asymmetrical. In the first two generations, responses were irregular; thereafter they were large in the low line (LLC) for two or three generations and then became small in comparison with those of the high line (HLC). At eleven generations of selection, the mean leukocyte count of HLC is about three times that of LLC Responses of the different cell types were proportional to their individual percentages of the total counts. There were sexual differences in the counts of total and individual cell types. Selection for total leukocyte counts affected the proportions of the individual cell types. Heritability estimates based on selection differential and response and on sib relationships yielded values ranging from 0·15 to 0·39.

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SELECTION FOR HIGH ADULT BODY WEIGHT IN DROSOPHILA POPULATIONS WITH DIFFERENT STRUCTURES

Genetics ◽

10.1093/genetics/81.1.163 ◽

1975 ◽

Vol 81 (1) ◽

pp. 163-175

Author(s):

A J Katz ◽

S S Y Young

Keyword(s):

Body Weight ◽

Random Mating ◽

Large Mass ◽

Mass Selection ◽

Adult Body ◽

Large Populations ◽

Subdivided Populations ◽

Adult Body Weight ◽

Selection For ◽

Selection Intensities

ABSTRACT Selection for high adult body weight in Drosophila melanogaster was practiced for 18 generations in three selection lines. These lines were genetically similar and of equal size but different in population structure. One line represented a large mass-selected, random-mating population, while the other two lines simulated large populations that had been subdivided into partial isolates or demes. Mass selection and random mating occurred within each deme. These two subdivided lines were different only in the rate of effective migration among the demes (5% and 10%). Selection intensities of approximately 20% were applied to these populations. A fourth line served as a random mating control. Heritability of adult body weight in the base population was estimated to be 0.58± 0.22. The results indicate that significantly greater responses were achieved in the subdivided lines than in the large mass-selected line, in spite of the fact that larger selection differentials were applied to the latter. No significant differences in response were observed between the two subdivided lines. Wright (1930, 1931) postulated that selection would be most efficient in subdivided populations with limited interdeme migration. The present findings appear to support this theory.

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