This book celebrates the importance of the question; it is not meant to be a collection of facts or procedures. The writing of this book was inspired by 16 years of queries from the research community.The con￾tributors and I have tried to meet two primary objectives:

Air Buoyancy Akin to water keeping something afloat, samples can be “lifted” by air, artificially decreasing their apparent weight. This air buoy￾ancy can have a significant effect on smaller samples. Electrostatic Forces Electrostatic charges are almost always present in any environ￾ment, particularly in areas with very low humidity. If there are

（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

◼ All DNA is recombinant DNA. ◼ Genetic exchange works constantly to blend and rearrange chromosomes, most obviously during meiosis, when homologous chromosomes pair prior to the first nuclear division. ◼ During this pairing, genetic exchange between the chromosomes occurs. This exchange, classically termed crossing over, is one of the results of homologous recombination

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’

1. Please define the term “mutation”, and list the major types of DNA mutations and their corresponding phenotypic effects. (20 points) 2. Please define the term “DNA lesion”. Please list the three types of DNA lesions and the chemical or physical mutagens cause these lesions. (20 points)

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)

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）不离开自己的座位。（2）收起书和笔记，不可放 在桌面上。（3）只能看和写自己的试卷（4）老师宣布 停的时候，所有学生必须放下自己的笔，眼睛 向前看。 （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）不离开自己的座位。（2）合上书和笔记。（3） 个人只能看和写自己的试卷（4）老师宣布停的时候， 所有学生必须放下自己的笔，眼睛 向前看。（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