英文基因.pptx

第1页/共9页 What are Genes?A gene is a unit of heredity in a living organism.It normally resides on a stretch of DNA that codes for a type of protein or for an RNA chain that has a function in the organism.编码蛋白质或编码蛋白质或RNARNA等等具有特定功能产物的具有特定功能产物的遗传信息的基本单位，遗传信息的基本单位，是染色体或基因组的是染色体或基因组的一段一段DNADNA序列序列 第2页/共9页Colloquial usage of the term“gene”(e.g.“good genes,”hair color gene“)may actually refer to an allele(等位基因):a“gene”is the basic instruction,a sequence of nucleic acid核酸(DNA or,in the case of certain viruses RNA),while an allele is one variant of that gene.Thus,when the mainstream press refers to having a gene for a specific trait,this may be incorrect.第3页/共9页In many cases,all people would have the gene in question,but certain people will have a specific allele(等位基因)of that gene,which results in the trait.In the simplest case,the changes observed may be caused by a single letter of the genetic code.第4页/共9页Genes hold the information to build and maintain an organisms cells and pass genetic traits to offspring,although some organelles(e.g.mitochondria线粒体线粒体)are self-replicating and are not coded for by the organisms DNA.第5页/共9页All living things depend on genes,as they specify all proteins and functional RNA chains.第6页/共9页StructureThe most common form of DNA in a cell is in a double helix structure(双螺旋结构),in which two individual DNA strands twist around each other in a right-handed spiral.In this structure,the base pairing rules specify that guanine pairs with cytosine and adenine pairs with thymine.第7页/共9页Chromosomes(染色体染色体)The total complement of genes in an organism or cell is known as its genome,which may be stored on one or more chromosomes;the region of the chromosome at which a particular gene is located is called its locus.A chromosome consists of a single,very long DNA helix on which thousands of genes are encoded.第8页/共9页Gene history第9页/共9页