A SEARCH FOR QUANTITATIVE TRAIT LOCI AFFECTING ASYMMETRY OF MANDIBULAR CHARACTERS IN MICE

An interval mapping procedure was used to search for and describe the effects of any quantitative trait loci (QTLs) for directional asymmetry (DA) and fluctuating asymmetry (FA) of 10 bilateral mandible characters in house mice. It was hypothesized that more QTLs would be found for DA than for FA, but that any discovered for FA should tend to exhibit dominance. All mandible characters were triply measured and 76 microsatellite markers were scored in an average of 471 mice from the F₂ intercross of the Large (LG/J) and Small (SM/J) inbred strains. A total of 16 QTLs significantly affected DA in nine of the 10 mandible characters, and this was more than the 9.5 expected by chance alone. These QTLs were found on seven of the 19 chromosomes, often at or near locations of QTLs affecting the mean of the two sides for various dimensions on the mandible. It was concluded that there is genetical variability for DA in these characters, although its level was low (4.4% of the total variation in this particular F₂ population). Eleven QTLs were detected for FA, suggesting that there is very little genetic variability for FA, at least as seen in the mandible characters in this particular F₂ population. As hypothesized, however, these QTLs did tend to exhibit dominance.