题目

组成玫瑰体内细胞的核酸的碱基、核苷酸的种类各有几种？（ ）              A．4种、4种              B．5种、8种               C．5种、4种              D．4种、8种 答案：解：根据五碳糖不同，核酸分为脱氧核糖核酸（DNA）和核糖核酸（RNA），玫瑰体中的核酸有DNA和RNA两种，DNA的基本组成单位是脱氧核苷酸，根据碱基不同脱氧核苷酸4分种，RNA的基本组成单位是核糖核苷酸，根据碱基不同核糖核苷酸也分4种，玫瑰内共有8种核苷酸，组成DNA的碱基有A、T、C、G，组成RNA的碱翻译下列句子。1. You should be quiet when you are in the reading room. ____________________________________________________2. When I grow up, I'll be a nurse and look after patients. ____________________________________________________3. If you don't want to go alone, I'll go with you. ____________________________________________________4. After you use plastic bags, you mustn't throw them about. ____________________________________________________5. People in the USA can't drink beer or wine before they reach 21. ____________________________________________________