问题
选择题
用显微镜观察紫色洋葱表皮细胞时,一般看不到染色体,这是因为( )
A.紫色液泡干扰了观察
B.染色体没有被染色
C.洋葱表皮细胞一般不分裂
D.洋葱表皮细胞无细胞核
答案
因为染色体在细胞有丝分裂时才会出现,平时是以染色质的形式存在,这是一种很细的东西,要电子显微镜 才能看到.洋葱表皮不再有丝分裂,所以看不到.
故选C.
用显微镜观察紫色洋葱表皮细胞时,一般看不到染色体,这是因为( )
A.紫色液泡干扰了观察
B.染色体没有被染色
C.洋葱表皮细胞一般不分裂
D.洋葱表皮细胞无细胞核
因为染色体在细胞有丝分裂时才会出现,平时是以染色质的形式存在,这是一种很细的东西,要电子显微镜 才能看到.洋葱表皮不再有丝分裂,所以看不到.
故选C.
完形填空。 | ||||
My English teacher is Lucy. She comes from England. She is 28 years 1 . She likes Chinese food. 2 favorite food is Chinese Jiaozi. She has a son and 3 boy was born (出生) on May 4th, 2007. My 4 is May 4th, too. It's interesting. Lucy's English classes are very 5 . She likes to play the games 6 the students in class. We all like her. She draws very 7 , and she often draws pictures for us after class. Today is her birthday. We come to her birthday 8 and give her many presents(礼物). She is very 9 . She says China is her second home. She 10 China very much. | ||||
|