阅读下面的诗歌 ，回答相关问题
                                                                                                     渡荆门送别
                                                                                                           李白
                                                                                         渡远荆门外，来从楚国游。
                                                                                         山随平野尽，江入大荒流。
                                                                                         月下飞天镜，云生结海楼。
                                                                                         仍怜故乡水，万里送行舟。

如图表示某家系中该遗传病的发病情况，下列叙述正确的是（　　）