Worm Breeder's Gazette 11(4): 73
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
We are interested in genes specifying life-history traits such as longevity, fertility, fecundity, and rate of development. Currently, we are looking for genes in the C1-balanced region of LGII that decrease hermaphrodite fertility. Since we hope to use deficiency stocks to map these genes, we have assayed the brood sizes of heterozygous deficiency stocks in order to establish the effects of deficiencies on fertility. We anticipated at least two ways that deficiencies might affect the brood sizes: (1) A negative correlation between size of deficiency and fertility could exist. This is based on a model where many genes would have additive effects on fertility, the classic assumption of quantitative genetics. (2) Certain genes might be haplo-insufficient such that one copy fails to make enough gene product for wild-type fertility to be expressed. We tested for a correlation between deficiency size and brood size using two different metrics of defining the deficiency size. First, we simply correlated the size of the deficiency in map units with brood size. We obtained a negative, but not significant correlation (- .28, P = .13). Second, we tried correlating the brood size with the number of known genes uncovered by each deficiency. This correlation was also negative and not significant (-.17, P = .36). Obviously, these results show no significant additive effects of deficiency size. In fact, the size of deficiency accounts for only 3 to 8% of the variance observed in brood size. We tested for haplo-insufficiency through a simple deficiency analysis, i.e., we looked for regions which gave a consistently reduced brood size when uncovered by a deficiency. We observed two regions that displayed a substantial decrease in fertility when uncovered by a deficiency. Stocks containing deficiencies of the dpy- 10 to spe-1 region or the let-237 to let-238, onsistently yield brood sizes of less than 150, while stocks containing deficiencies that border these regions produce broods of 150 and above. Therefore, our results do show some evidence for haplo-insufficient sites. In conclusion, our analysis of the effects of LGII deficiencies on brood size does not show any evidence of additivity based on number of genes removed. We do detect haplo-insufficient regions where codominant fertility mutations might be found by mutation. We will continue screening for low-brood mutants and plan to map these fertility mutations through deficiency mapping.