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Analysis of quantitative inheritance of body size in mice: V. Effects of small numbers of polygenes on similar genetic backgrounds*
Published online by Cambridge University Press: 14 April 2009
Extract
Sublines carrying isolated polygenes determining body size, developed by selection and repeated backcrossing to the LG and SM strains of mice, were inbred by full-sib matings with concomitant selection to study the inheritance of body size, using birth, weaning (28-day) and 60-day body weights as indices.
Mean body weights in those sublines backcrossed to SM and selected for large body size were greater than in those selected for small body size, proving that the difference resulting from seven earlier generations of backcrossing and selection, although small, was genetic and could be fixed by inbreeding. The mean body weights of the sublines selected for small body size drifted upward despite downward selection, a phenomenon thought to be due to the pressure of natural selection outweighing that of artificial selection.
In the sublines developed from backcrosses to the LG strain, mice from lines selected for small body size attained a mean body weight greater than that of mice from lines selected for large body size and also than of the parental LG strain. These results were contrary to expectation and a genetic interpretation was offered.
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- Copyright © Cambridge University Press 1968
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