问题 单项选择题

果蝇幼虫唾液腺细胞在分裂间期,某一条染色体多次复制后而不分开,形成了一种特殊的巨大染色体(如下图所示)。若用3H标记的尿嘧啶掺入染色体,在胀泡中3H含量较高,而且随着幼虫发育的进行,胀泡在同一染色体不同位点出现或消失。下列相关推测最合理的是()

A.胀泡的出现是DNA分子复制出现了差错

B.被标记的尿嘧啶是催化mRNA合成的酶

C.胀泡的出现与特定基因的表达有关

D.胀泡的出现是染色体结构变异的结果

答案

参考答案:C

解析:尿嘧啶是RNA的特有碱基,与基因的转录和翻译有关,与DNA复制无关,A项错误;起催化作用的酶化学本质是蛋白质,尿嘧啶只是含氮的碱基,B项错误;胀泡在同一染色体的不同位点出现或消失,说明胀泡的出现与特定基因的表达有关,C项正确、D项错误。考点:本题利用同位素标志法来考查考查DNA复制、表达等知识,意在考查考生能运用所学知识与观点,通过比较、分析与综合等方法对某些生物学问题进行解释、推理,做出合理的判断的能力。

阅读理解

The Bear Valley Teen Adventure Camp is a high-energy experience focusing on safe outdoor climbing and an appreciation for the natural environment. Along the way campers can also swim, hike, and canoe (划独木舟). The instructors are professional educators who can increase your teens’ confidence, teamwork and climbing skills. All climbing abilities are welcome and no previous outdoor rock climbing experience is required. Participants (参加者) can choose Day Camp or Overnight Camp. In addition, campers learn to appreciate the wild as well. We look forward to seeing your teenagers smile this summer.

Day Camp includes six adventurous days of rock climbing, hiking, swimming, and canoeing in beautiful Bear Valley. Our focus is climbing but we use additional activities to keep things lively. Instructions and skill development are provided. No experience is required and all equipment is provided. On the last day parents are welcome to join us for a big lunch to hear all about the adventures of camp for nothing.

Overnight campers can get the full experience with family-style meals, evening activities and top accommodations (住宿) at the BaseCamp Lodge in Bear Valley. A typical schedule is that after Day Camp, campers get a short rest and snack before getting together for a hike or swim. Afterwards, a delicious meal is served as tales from the day are shared around the table.

Dates: July 22-28, 2013

Costs: $575 – Day Camp (6 days + lunches)

$975 – Overnight Camp (7 days, 6 nights & all meals)

Ages: 10-16 years old

小题1:Bear Valley Teen Adventure Camp ________.

A.is aimed at increasing teens’ confidence in their studies

B.requires participants to have all climbing abilities

C.focuses on protecting the natural environment

D.will provide campers with instructions小题2:According to the second paragraph, we learn that ________.

A.Day Camp doesn’t provide equipment

B.parents can have lunch for free on the last day

C.Day Camp has no other activities besides climbing

D.Day Camp provides campers with a meal in the evening小题3:What can we learn about Overnight Camp?

A.It requires parents to prepare meals for campers.

B.Campers can have a snack before Day Camp.

C.$975 only includes 7 days, 6 nights and 6 lunches.

D.Campers can share stories with others when having meals.

多项选择题