高级植物生理绪论教程.ppt

The DNA molecule stores the organisms genetic information and coordinates the metabolic processes of life. Genetic information is specified by the sequence of four chemical bases (adenine A, cytosine C, guanine G, and thymine T) along the length of the DNA molecule. A gene is a segment of DNA with a message (instruction) to encode the information necessary for assembly of a specific protein. The proteins then function as enzymes to catalyze biochemical reactions, or as structural or storage units of a cell, to contribute to expression of a trait. Scientists understand now the coding system of the genes that are passed from one generation to the next, which gives them the opportunity to change the instruction carried by genes. The introduction of new instructions would cause a cell to produce products that can be beneficial to people. These discoveries make genetic engineering possible: 1) DNA is found everywhere 2) using a restriction enzyme (biological scissors) that are able to cut the DNA molecule in a specific manner 3) Possibility to use natural vectors that are able to insert a specific piece of DNA (gene) in to a cell Roug guide to genetic engineering Isolate DNA. Treat it with enzymes which cut the DNA into gene-sized pieces. Force the genes into special strains of bacteria (or viruses) so that on average each bacterium contains one piece of DNA. Grow colonies of the bacteria and screen for the presence of the gene in question. Select the most suitable gene carrier and grow that clone to give milligram amounts of the gene Sequence and trim the genes, and add special DNA signals (promoters). Insert into the DNA of another organism (virus, bacterium, plant or animal). How do we extract a gene from one organism, introduce it into another organism and, most importantly, get it to work there?  Future directions for transgenic plants and their potential benefits for people A gene is a DNA segment that encodes a specific protein that contributes to expression