试题与答案

用3H标记的胸腺嘧啶脱氧核苷酸培养某种细胞一段时间后,再移至普通培养基中培养,不

题型:选择题

题目:

3H标记的胸腺嘧啶脱氧核苷酸培养某种细胞一段时间后,再移至普通培养基中培养,不同间隔时间取样,进行放射显影,在显微镜下观察计数,统计标记细胞的百分数,图中A:细胞核开始被标记;B:一个被标记细胞X开始进入分裂期;C:细胞X着丝点开始分裂;D:细胞X分裂成两个子细胞,被标记细胞数目在增加;E:标记细胞第二次进入分裂期;F:被标记细胞的比例在减少;G:被标记细胞的数目在减少。下列说法中,错误的是

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A.该细胞分裂一次平均经历的时间为10h

B.图甲中BC段DNA分子稳定性最低,适于进行诱发突变

C.被标记的细胞比例减少的根本原因是DNA有半保留复制的特点,在普通培养基中,新合成的脱氧核苷酸链都是没被标记的

D.图乙分裂状态位于图甲的CD期的前段,细胞内含有4个染色体组

答案:

答案:B

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题型:单项选择题

The first and most important agents of socialization are the people who care for infants. In the earliest months, messages from nurturers constitute the child’’s basic understanding of the world around it. This is the infant’’s first introduction to the language that shapes perception and elicits emotion.Another powerful source of information and socialization is the friendship of peers. Peers are equals that one can deal with on the same level as oneself, whereas parents are superiors. The heavy emotional overlay of family relationships makes some kinds of learning difficult.Much formal socialization is placed in the hands of professionals. Teachers from kindergarten on are specifically designated agents of socialization. Ideally, a teacher is one who has both knowledge and the skills to present it. During the course of teaching their subjects, classroom instructors provide role models and attempt to convey the excitement of learning itself.In earlier times, parents, friends and teachers would comprise the list of primary childhood socializers. Children’’s books, comics and magazines might also have been mentioned as sources of information on norms and role models. Today one must add three powerful indirect or non-personal socialization agents: radio, movies and television. Many people learn about politics, form a vision of well-being, and develop attitudes towards others from what they see on the screen and hear through the speakers.

The child’s basic understanding of the world around it is formed________.

A.at kindergarten

B.in the earliest months

C.by classroom instructors

D.through interaction with parents

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