中国地方鸡品种多具有青胫的特征，其被认为代表了中国本地鸡的特征而受消费者青睐。控制胫色的基因座位Id位于Z染色体上末端，但由于Z染色体末端序列结构复杂，且胫色表型的遗传模式复杂，Id位点的基因定位进展困难。申请人在前期研究中通过建立寿光鸡与农大C系的高代回交群体，减少遗传背景对于寿光鸡中的青胫位点id的干扰，将id定位于Z染色体上的78.85Mb，并找到3个与胫色表型紧密连锁的SNP标记。本项目拟进行Z染色体单体分离并测序，通过对Z染色体重新组装来解析Z染色体末端复杂序列特点，从该区域内新基因或已知基因中找到Id基因，并根据基因表达模式和胫部黑色素细胞分布模式的比对进行Id候选基因验证。研究Z染色体末端的复杂序列结构对于Id座位候选基因表达与表型的影响。本项目旨在精确解析Z染色体的复杂序列，并进一步定位Id基因，对于青胫性状等性染色体连锁性状的鸡育种有着重要价值。

Most of the local Chinese chickens have characteristics of the dark shank, which is considered a representative trait of local Chinese chickens, and thus the dark shank is preferred by consumers. The locus Id, which controls shank color, has been reported to be located at the telomere the Z chromosome. However, due to the fact that the shank color phenotype may be regulated by multiple genes and the genetic pattern is complicated, it is difficult to map the Id locus precisely. In the preliminary research of the project, we built up an advanced backcross mapping population using Shouguang and Nongda C line. Therefore, the confounding effects of genetic background on the Id locus were reduced and controlled by applying family information. Finally, we mapped the Id locus at 78.85Mb on the Z chromosome, and found three SNPs closely linked with the shank color trait. This project intends to obtain correct sequences and gene annotation of Z chromosome by separating and sequencing the Z chromosome molecule component. This project will clarify the sequence complexity and gene annotation on the Z chromosome, and analyze the possibility of novel genes or previously annotated genes in this region as Id candidate genes. Then validate the candidate gene by comparing the their expression patterns and the distribution of melanocytes on the shank. We intend to clarify the regulation mechanism of shank color trait by investigating the relationship between the candidate genes of Id locus on Z chromosome. All these studies will provide a new view of the Id mapping and its genetic mechanism of regulating the shank color trait. Our work will also provide important information for the chicken breeding of shank color trait and other sex-linked traits.