基因工程Chapter 2.docx

1、基因工程Chapter 2基因工程原理The principles of Gene engineeringChapter1 Gene & Gene engineering1. Development of Gene study What is gene engineering?It is a new science in biological technology set up in 1970s based on the comprehensive progress of molecular biology and molecular genetics1 st stage :Before 50

2、s. chromosome 2 nd stage: after 50s80s,large molecular _ molecular biology3 nd stage: from 80s_gene function _phenotype relationship _Reverse biology (R_genetics)1基因学说的创立 Step up of Gene theory2 基因与DNA分子 Gene and DNA molecular What is gene?1953 WatsonCrick double helix model.Every organism possesses

3、 a genome that contains the biological information needed to construct and maintain a living example of that organism Most genomes including those for all cellular life forms, are made of DNA (Deoxyribonucleic acid ),but a few viruses have RNA (Ribonucleic acid) genomes.DNA and RNA are polymeric mol

4、ecules made up of linear, unbranched chains of monomeric subunits called nucleotides. Each nucleotide has threes parts: a sugar a phosphate group and a base. In DNA, the sugar is 2_deoxyribose and the bases are adenine(A), cytosine(C), guanine(G), and thymine(T).Nucleotides are linked to one another

5、 by phosphodiester bonds to form a DNA polymer, or polynucleotide. Which might be several million nucleotides in length, DNA in living cells is doublestrand, two polynucleotides being wound around are another to form the double helix. The double helix is held together by hydrogen bonds between the b

6、ase components of the neucleotides in the two strands. The base-pairing rules are that A base-pairs with T, and G base-pairs with C. The two Dna molecules in a double helix therefore have complementary sequences .In an RNA nucleotide the sugar is ribose rather them 2-deoxyribose, and thymine is repl

7、aced by the related base uracil (U). RNA polymers are rarely more them a few thousand nucleotides in length, and RNA in the cell is usually single-stranded, although base pairs might form, between different parts of a single molecule. The biological information contained in a genome is encoded in th

8、e nucleotide sequence of its DNA or RNA molecules and is divided into discrete units called genes. The information contained in a gene is read by proteins that attach to the genomes, this process was originally looked on as comprising two stages, transcription and the second resulting in synthesis o

9、f a protein whose amino acid sequence is determined, via the genetic code, by the nucleotide sequence of the RNA transcriptThe genome is the entire DNA content of a cell, including all of the genes and all of the intergenic regions. A complete copy of the genome must be made every time a cell divide

10、s. DNA replication has to be extremely accurate in order to avoid the introduction of mutations into the genome copies Some mutations do , however , occur, either as errors in replication or due to the effects of chemical and physical mutagene that directly alter the chemical structure of DNA, DNA r

11、epair enzymes correct many of these errors; those that escape the repair processes become permanent features of the lineage descending from the original mutated genome. These events, along with genome rearrangements resulting from recombination underlie molecular evolution, the diving force behind t

12、he evolution of living organisms.The human genome contains approximately 80000 genes, but the coding region of these genes take up only 3% the genome.The yeast genome contains 6000 genes and has a more compact organization.The genomes of some plants are dominated by repetitive DNA sequence.Although

13、the basic physical structures of all eukaryotic nuclear genomes are similar, one important feature is very different organisms. This is genome size, the smallest eukaryotic genomes being less them 10Mb in length, and the largest over 100000Mb. Genome sizes of some organismsOrganismGenome size(Mb)Pro

14、karyoteMycoplasma genitalium0.58Escherichia coli4.64Bacillus megaterium30EukaryoteFungiSaccharomyces cerevisiae (yeast)12.1Aspergillus nidulans25.4Magnaporthe grisea38. 8 OrganismGenome size(Mb)Protozoa (原生动物)Tetrahymena pyriformis190Invertebrates (无脊椎动物)Caenorhabditis elegans (Nematode worm)100Dros

15、ophila metanogoaster (fruit fly)140Bombyx mon (silkworm)490Strongylocentrotus purpuratus (sea urchin 海胆)845Locusta migratoria (locust)5000 OrganismGenome size(Mb)VertebrateFugu rubripes (puffer fish)400Homo sapiens (human)3000Mus musculus (mouse)3300 OrganismGenome size(Mb)PlantArabidopsis thaliana (vetch)100Oryza sativa (rice)565Pisum sativum (pea)4800Zea mays (maize)5000Triticum aestivum (wheat)17000Fritillaria assyriaca (fritillary 贝母)120000 3 基因与DNA的多核苷酸区段 Gene and polynucleotide fragment of DNA传统的基因概念：基因是成串地在DNA分子上一个接一个地排列着，它们之间由非遗传物质连接起来，交换在基因