Chase Kevin, Carrier David R, Adler Frederick R, Ostrander Elaine A, Lark Karl G
University of Utah, Department of Biology, Salt Lake City, Utah 84112, USA.
Genome Res. 2005 Dec;15(12):1820-4. doi: 10.1101/gr.3712705.
Size sexual dimorphism occurs in almost all mammals. In Portuguese Water Dogs, much of the difference in skeletal size between females and males is due to the interaction between a Quantitative Trait Locus (QTL) on the X-chromosome and a QTL linked to Insulin-like Growth Factor 1 (IGF-1) on the CFA 15 autosome. In females, the haplotype of CFA 15 resulting in small size is dominant. In males, the haplotype for large size is dominant. Females, homozygous at the CHM marker on the X chromosome and homozygous for the large size CFA 15 haplotype are, on average, as large as large males. However, all females that are heterozygous at the CHM marker are small, regardless of their CFA 15 genotype. This interaction suggests a genetic mechanism that in turn leads to a scenario for the evolution of size sexual dimorphism consistent with a proposal of Lande that sexual dimorphism can evolve because females secondarily become smaller than males as a consequence of natural selection for optimal size. Our results also can explain Rensch's Rule, which states that size is often positively correlated with the level of size sexual dimorphism.
体型两性异形几乎存在于所有哺乳动物中。在葡萄牙水犬中，雌性和雄性之间骨骼大小的差异很大程度上是由于X染色体上的一个数量性状基因座（QTL）与犬15号常染色体上与胰岛素样生长因子1（IGF-1）相关的一个QTL之间的相互作用。在雌性中，导致体型小的犬15号单倍型是显性的。在雄性中，导致体型大的单倍型是显性的。在X染色体上的CHM标记处纯合且犬15号大尺寸单倍型纯合的雌性，平均而言与大体型雄性一样大。然而，在CHM标记处杂合的所有雌性都体型小，无论它们的犬15号基因型如何。这种相互作用表明了一种遗传机制，进而导致了一种体型两性异形进化的情形，这与兰德的提议一致，即两性异形可以进化是因为由于对最佳体型的自然选择，雌性随后变得比雄性小。我们的结果也可以解释伦施法则，该法则指出体型通常与体型两性异形的程度呈正相关。
