玉米( 2n=20 )种群中偶尔会出现一株三体植物( 5 号染色体有 3 条)。在减数分裂时,这三条染色体的任意两条向细胞一极移动,剩下一条移向另一极,细胞中其余同源染色体正常分离。若控制玉米高杆、矮杆的基因分别是 A 、 a ,且当体细胞中 a 基因数多于 A 基因时, A 基因不能表达。下列关于三体玉米(基因型 Aaa )的叙述,错误的是
【简答题】Every year there is the Spring Festival in China. Usually it is in January or February. It’s the most important festival in China. So before it comes, everyone has to prepare things. They buy beef, ...