（1）桌上只许有笔，答题纸和英文课本。（2）不许 离开自己的座位。（3）不许偷看，不许讲话 (有问题 举手）（4）老师宣布停的时候，必须放下自己的笔。 （5）老师宣布收试卷时，试卷必须快速由每排的最左 边传向右边，每排最右边的同学负责把试卷交给当堂 助教

（1）桌上只许有笔，答题纸和英文课本。（2）不许 离开自己的座位。（3）不许偷看，不许讲话 (有问题 举手）（4）老师宣布停的时候，必须放下自己的笔。 （5）老师宣布收试卷时，试卷必须快速由每排的最左 边传向右边，每排最右边的同学负责把试卷交给当堂 助教

（1）桌上只有笔和答题纸。（2）不离开自己的座位。 （3）不偷看，不讲话 (有问题举手）（4）老师宣布停 的时候，必须放下自己的笔。（5）老师宣布收试卷时， 试卷必须快速由每排的最左边传向右边，每排最右边 的同学负责把试卷交给当堂助教

Describing the following terms (4 points each) 1. Cre recombinase 2. CSSR recombination 3. Mating-type switching 4. Mismatch repair 5. Polymerase switching 6. 30-nm fiber 7. Core histones

1. Please describe the main features of the DNA structure. (10 points) Key features: (1) Double helical structure (4’) (2) Two strands are held together in an antiparallel orientation (3’) by base paring (1’)

1. What are the gene expression stages that can be regulated? (10 points) Regulated stages in gene expression: (1) transcription initiation (the most important stage): RNAP binding of the promoter, transition from the closed complex to the open complex; promoter escape 4’ (2) stages after initiation (elongation and termination) 2’ (3) RNA processing (alternative splicing) in eukaryotes 2’ (4) translation 2’

Q1: Please name the following amino acids (three letter name, for example: Ala for alanine). Q2: Which of them are hydrophobic AA, and which are hydrophilic?

Q1. Prokaryotic cell E. coli consists of a single closed-circular DNA molecule of 4.6 x 106 bp long. This DNA molecule would be 1.6 mm if the double helix is relaxed. Please describe what strategies does E. coli use to pack such a long molecules into its nucleoid less than a micrometer (mm) in diameter. (20 points)

（1）开卷考试，个人独立完成 （2）不须偷看别人的答案 （3）老师宣布收试卷时，试卷必须快速由每排的最左

1. What is “DNA cloning”? how could you make a genomic library cloning? (30 points) 2. What is “subcloning”? What are the purposes of subcloning. (15 points)