728生态学电子浙里课件复习

1、24 Genes and ChromosomeChromosome: A single large DNA molecule and its asso stores and transmits genetic information.ted proteins, containing many genes;Gene: A chromosomal segmentt codes for a single functional polypeptide chain or RNAmolecule.Regulatory Sequen: A DNA sequence involved in regulatin

2、g the expresofagene(promoter and/or operator)Genes and Chromosome* Chromosomal ElementsMuions: An inheritable changehe nucleotide sequence of a chromosome.One gene-one proteinEukaryotic Chromosomes Are Very Complex Centromere: the region of a eukaryoticspecific for each species.chromosometisattached

3、tothespindle 纺锤体 during nuclear divi. Itis defined genetically as the region of thechromosomet always segregatesof meiosis 解释是减数和第二次减数atthedivi但我认为是有丝; i.e.the region of the chromosome in which nocrossiner occursomeres: the structuret seals 封 theend of a chromosomet help stabilize the chromosome. In

4、 order to counteractthe tendency of the chromosome otherwiseto shorten with each round of replication,theomeric DNA consists of simpletandemly 衔 接 着 repeatedsequenSalite DNA; a fraction 片段 of DNA, presentost eukaryotic cells in amounts of up to10% or more of total DNA, wihighly repetitive nucleotide

5、 sequence. It is found outsidecoding regions and to ocuur in lengths of up to fewdred bp.Minisalite DNA; a repeat DNA segment comprising short head-to-tail tandem 一前一后repeats giving variable number tandem repeat type polymorphisms 多样性 , withapproximate size betn 1 and 30 bp.DNA fingring (genetic pro

6、filing); a technique for providing profiles of DNA fragments(resulting from digestion with restriction 限制 enzymes) t characterize a genome. Regions of DNA consisting of tandem repeats of short base sequence which can show extensive variation in the number of repeats, leading to multi-allelic variati

7、on and high degrees of heterozygosity 杂合性. This extreme level of variation randers minisa lite orvariable number tandem repeats loci invaluable 无价 as genetic markers.Many Eukaryotic Genes ContainerveningMany genes in eukaryotic cells, and very occaNontranscribed Sequenally in bacteria, are(rons)erru

8、pted bynoncoding sequencalledrons. The coding segments separated byrons are calledexons.Hydrid 杂交* The Size and Sequentructure of DNA MoleculesThe chromosome of an E. Coli cell is a single double-stranded circular DNA molecule (4,639,221 base pairs).Bacteria Contain Chromosomes and Extrachromosomal

9、DNAplasmids. Strictly any extrachromosomal genetic element (mitochondrial and choroplasts DNA are excluded), hence the term plasmid generally refers to an extrachromosomalcovalently continuous double-stranded DNA moleculet occurs in bacteria and othermicroanisms (rarely). Plasmids are popular choifo

10、r cloning vectors.Natural plasmids vary from 5 to over 90 kp in size. Plasmid genes include druggenes for catabolic enzymes, antibiotic synthesis and toxin production.,Eukaryotic Cells Contaore DNAn ProkaryotesMitochondria and Chloroplasts Probably Evolved from Endosymbiotic Bacteria anelles of Euka

11、ryotic Cells Also Contain DNA* DNA SupercoilingCellular DNA is highly compacted 紧凑的, implying a high degree of structural The folding mechanism must not only pack the DNA but also permit acanization.s to theconformationhe DNA.DNA supercoiling (coiled coil DNA); A form of circular double-stranded DNA

12、 in which the double helix coils around itself like a twisted rubber band, and the supercoiling is induced by separating strands of a helical structure.Most Cellular DNA Is Underwound ？DNA Underwinding Is Defined by Topological Linking NumberTopoisomers; any of two or more isomers 异构体 of a macrocycl

13、ic molecule, or system oftwo or more macrocyclic moleculest differ in the degree of knotting of a loop or thedegree oferloking of rings.Two forms of a given circular DNAt differ only in a topological property such as linkingnumber are referred to as DNA topoisomers.Topoisomerases; any enzymet alters

14、 superhelix density in supercoiled DNA. Theenzymes increase or decrease the extent of DNA underwinding are called topoisomerases,and include Type I and II.Type I; Act by transiently breaking one of the two DNA strands, roing one ofsabout the broken strand and rejoining the broken ends; they change lk in increments of 1.Type II; Break both DNA strands and change lk in increment of 2.Gyrase;