1. A、B两种不同细菌之DNA中所含的adenine 硷基各为40%、10%，请分析A、B细菌 genomic DNA中所含的4 种硷基所占的百分比为何？哪依各菌朱试教有可能生长在温泉环 境中？ 2. 课本习题8 3. Heteroduplexes made up of one strand of DNA and one strand of RNA typically form an A-form helix. Please give an explanation that explains the preference of the heteroduplex for A-form and B-form helix. 4. Why would reducing the concentration of salts (lowering the ionic strength) in a solution of double-stranded DNA lower the melting point of the DNA? 5. Two molecules of double-stranded DNA are the same length (1000 base pairs), but differ in base composition. Molecule 1 contains 20% A+T; molecule 2 contains 60%A+T. Which molecule has a higher tm (melting point)? How many C residues are ther in the 60% A+T DNA molecule? (A) 2: 40 (B) 1: 200 (C) 2; 400 (D) 1; 400 (E) 2; 200 6. You wish to determine the relative degree of sequence similarity for DNA from different species of Galapagos finches (referred to as species A, B, C). You make hybrid duplexes of the DNA between A and B, A and C, and B and C. You measure the increase in the absorption of UV light with increasing temperature for each of the duplex solutions and obtain the following data: Hyvrid duplex tm A+B 80℃ A+C 87℃ B+C 83℃ (a) Which two species have a greater degree of similarity in their DNA sequences? Why? (b) What factors should be taken into account when interpreting these data? 7. 请画出single strand 的详细化学构造; DNA G-A-C-T-T，并画出其互补之RNA化学构 造。 8. Please describe the effects of spontaneous deamination of C to U, or 5-methyl-C to T, on the next DNA replication? 9 .Read Assigned reading “ Your Genes, Your Choices “ Chapter 1 &2 ● (1)请用A4纸书写。 (2)不用抄题。 (3)缴交时间：_ 老师说希望 礼拜三 五点以 前作业可以缴交到 她的办公室 因此，请在 礼拜三 上生化课 《前》 统一缴交给 班代 甲班请交给 阿法 乙班请交给 彦廷 因为乙班三点还有课，所以可能需要麻烦 阿法 送往 医学大楼 二楼 生化科办公室 给 李妙蓉老师 谢谢大家的配合 --

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