分子进化2019分子进化molevo07

1、分子进化学MolecularEvolution雷霆华中农业大学生命科学技术学院Tel: 87282669Email: 2012年10月1第七章 基因组的进化2GenomeSize34Composition of human genomeExons (1.5%)Introns (5%)Regulatory sequences (20%)Repetitive DNA that includes transposable elements and related sequences (44%)GenomeComplexityUnique noncodi

2、ng DNA (15%)L1sequences (17%)Repetitive DNAunrelated to transposable elements (14%)Alu elements (10%)Large-segmentduplications (5-6%)Simple sequence DNA (3%)Duplication, rearrangement, andmutation of DNA contribute to genome evolutionThe basis of change at the genomic level is mutation, which underl

3、ies much of genome evolutionThe earliest forms of life likely had a minimal number of genes, including only those necessary for survival and reproductionThe size of genomes has increased over evolutionary time, with the extra genetic material providing raw material for gene diversification5基因复制基因删除外

4、显子重排Five types of change contribute to genome evolution水平基因转移67Gene duplications Slipped strand mispairing8Gene duplications Unequal crossover during recombinationGene duplication allows for the acquisitionof new functional genes in the genome9实例：珠蛋白基因的进化b-Globina-GlobinHemea-Globin gene familyChrom

5、osome 16b-Globin gene familyChromosome 11yzybdzyaa2 a1ebyayqAgGg21Fetus and adultEmbryoEmbryo FetusAdult(b) The human a-globin and b-globin gene families1011A model for the evolution of the human a-globin and b-globin gene families from a single ancestral globin gene.12Ancestral globin gene (present

6、 in primitive animals) was duplicated 500 mya.PrimatesMammals13Duplication of Entire Chromosome SetsAccidents in meiosis can lead to one or more extra sets of chromosomes, a condition known as polyploidyHuman chromosome 2Chimpanzee chromosomesThe genes in one or more of the extra sets can diverge by

7、 accumulating mutations; these variations may persist if the organism carrying them survives and reproducesTelomeresequencesCentromere sequencesTelomere-like sequencesCentromere-like sequences12Human chromosome 16Mouse chromosomes13781617(a) Human and chimpanzee chromosomes(b) Human and mouse chromo

8、somesGene DuplicationAlmost every gene in the vertebrate genome exists in multiple copiesGene duplication allows for new functions to arise without having to start from scratchStudies suggest the early in vertebrate evolution the entire genome was duplicated at least twiceExon DuplicationDuplication

9、s are not limited to entire genes Proteins are often collections of distinct amino aciddomains that are encoded by individual exons in a geneThe separation of exons by introns facilitates the duplication of exons and individual gene evolution14Exon ShufflingThe exons of genes can sometimes be though

10、t of as individual useful units that can be mixed and matched through exon shuffling to generate new, useful combinations1516实例：TPA基因的进化EGFEGFEGFEGFEpidermal growthfactor gene with multiple EGF exonsExon shufflingExon duplicationFFFFFibronectin gene with multiple “finger” exonsFEGFKKKPlasminogen gen

11、e with a “kringle” exonExon shufflingPortions of ancestral genesTPA gene as it exists todayMobile elements contribute togenomeevolution in severalways Exon shuffling Insertion mutagenesis Homologous and non- homologous recombination17转座子的类型TransposonRetrotransposon18转座子可引起外显子重排Exon shuffling via SIN

12、E mobilizationintronexon 2DNA copy of transcriptSINE transcription can extend past the normal stop signalReverse transcription creates DNA copies of both the SINE and exon 2Reinsertion occurs elsewhere in the genome19exon 2exon 1Nonsister chromatidsTransposable elementGene转座子可导致非对称交换CrossoverpointIncorrect pairing of two homologs during meiosis基因复制and2021H