墨西哥是吉娃娃的故乡，而中国西藏则培育出了狮子狗。然而一项最新的遗传分析表明，所有的小狗都起源于中东
狗的起源一直是进化生物学上的热点问题。科学家认同它们是由灰狼驯化而来的，但对于这一切究竟发生在哪里却各执一词。如今，科学家通过对核子DNA的分析终于解开了这个谜题。研究人员发现，一个名为IGF1的基因在小狗中很普遍，但在大型犬以及野狗中却罕有发现。然而这一基因的一个非常类似的版本却存在于中东地区的灰狼中。这意味着该地区可能就是全世界小狗的起源地。研究人员在最新出版的《BMC生物学》杂志上报告了这一发现。
推荐原始出处：
BMC Biology 2010, 8:16doi:10.1186/1741-7007-8-16
The IGF1 small dog haplotype is derived from Middle Eastern gray wolves
Melissa M. Gray , Nathan B. Sutter , Elaine A. Ostrander and Robert K. Wayne
Background
A selective sweep containing the insulin-like growth factor 1 (IGF1) gene is associated with size variation in domestic dogs. Intron 2 of IGF1 contains a SINE element and single nucleotide polymorphism (SNP) found in all small dog breeds that is almost entirely absent from large breeds. In this study, we surveyed a large sample of grey wolf populations to better understand the ancestral pattern of variation at IGF1 with a particular focus on the distribution of the small dog haplotype and its relationship to the origin of the dog.
Results
We present DNA sequence data that confirms the absence of the derived small SNP allele in the intron 2 region of IGF1 in a large sample of grey wolves and further establishes the absence of a small dog associated SINE element in all wild canids and most large dog breeds. Grey wolf haplotypes from the Middle East have higher nucleotide diversity suggesting an origin there. Additionally, PCA and phylogenetic analyses suggests a closer kinship of the small domestic dog IGF1 haplotype with those from Middle Eastern grey wolves.
Conclusions
The absence of both the SINE element and SNP allele in grey wolves suggests that the mutation for small body size post-dates the domestication of dogs. However, because all small dogs possess these diagnostic mutations, the mutations likely arose early in the history of domestic dogs. Our results show that the small dog haplotype is closely related to those in Middle Eastern wolves and is consistent with an ancient origin of the small dog haplotype there. Thus, in concordance with past archeological studies, our molecular analysis is consistent with the early evolution of small size in dogs from the Middle East.
