polymerase links free nucleotides as they line up on the template formed by the original strand of the parent molecule.
In eukaryotes DNA replication follows the same general principles as in prokarotes. On the long DNA molecules replication proceeds (in two directions at once) from hundreds or thousands of points of origin.
大肠杆菌复制开始时形成泡样复制叉，链生长方向由5′向3′端，前导链连续生成，后随链由冈崎片段组成，由DNA聚合酶催化。真核生物复制与原核生物复制相似，但有几百到几千个复制原点（原核一般只有一个复制原点）。
课后作业：第一篇阅读材料
答案：1C,2C,3B,4A,5D,6D,7B
Glossary
one-gene-one-enzyme hypothesis 一基因一酶假说
The hypothesis that a large class of gene exist in which each gene controls the synthesis or activity of but a single enzyme. Since enzymes and other proteins whose syntheses are controlled by more than one gene are now known, this hypothesis has been replaced by the one-gene-one polypeptide hypothesis.
one-gene-one-polypeptide hypothesis一基因一多肽假说
The hypothesis that a large class of genes exist in which each gene controls the synthesis of a single polypeptide. The polypeptide may function independently or as a subunit of a more complex protein.
adenine 腺嘌呤
A purine base that is an essential constituent of the nucleic acids and also of such coenzymes as NAD and FAD.
guanine 鸟嘌呤
A double-ring nitrogenous base molecule in DNA and RNA. It is the complementary base of cytosine.
cytosine胞嘧啶
A single-ring nitrogenous base molecule in DNA and RNA. It is complementary to guanine. thymine 胸腺嘧啶
A single-ring nitrogenous base molecule of DNA but not RNA. It is complementary to adenine. purine 嘌呤
One of a group of nitrogenous bases whose parent compound has the formula shown. The two most abundant purines are adenine and guanine, which are constituents of nucleic acids and coenzymes.
pyrimidine 嘧啶
A heterocyclic organic compound, C4N4N2 the fundamental form of pyrimidine bases. Some of these bases are constituents of nucleic acid.
nucleoside 核苷
A purine or pyrimidine base attached to ribose or deoxyribose. The nucleosides commonly found in DNA and RNA are: cytidine, cytosine deoxyriboside, thymidine, uridine, adenosine, adenine deoxyriboside, guanosine, and guanine deoxyriboside. Note that thymidine is a deoxyriboside and cytidine, uridine, adenosine,and guanosine are ribosides.
X-ray diffraction X射线衍射
A technique for determining the arrangement of atoms in a crystalline substance by analysing the diffraction patterns produced when a narrow beam of X-rays is passed through the substance. X-ray diffraction has contributed to the elucidation of structure of many biological molecules, including some important macromolecules, e.g., DNA, haemoglobin, myoglobin.
DNA double helix 双螺旋
The three-dimensional structure of doublestranded DNA.