超好研究生分子生物学课件-真核基因组2.ppt

Eukaryotic chromosome,,Loops of 30nm fiber,DNA 片段,核小体串,30 nm 纤维,300 nm,间期染色体片段,染色体,2 nm,11 nm,30 nm,300 nm,700 nm,1400 nm,1, the sister chromatids at mitosis represents the most highly condensed state of chromatin.,Centromere,Telomere,Loops of 30 nm fiber,,,,chromatid,,The linear DNA traces a single path from one tip of the chromosome to the other, successive loops of up to 100 kb of 30 nm fiber anchored to the nuclear matrix in the core.,2, the centromere is the region where the chromatids are joint and is also the site of attachment, via the kinetochore, to the mitotic spindle where pulls apart the sister chromatids at anaphase. Centromeres are characterized by satellite DNA in mammalian cells.,3, telomeresThe end of the linear chromosomal DNA are protected from degradation and gradual shortening by the telomeres, which are short repeating sequences synthesized by telomerase, independently of normal DNA replication.,Characters of eukaryotic genome1, all the eukaryotic genomes are DNA, the genome of somatic cell is diploid, and haploid for the gamete cell. 2, huge numbers of genes; structural complex; multiple origins of replication.,3. The transcripts are monocistrons; without operons like those in bacteria. 4, noncoding sequences account to over 90 % 0f full genome.,5, big amount of repeated sequences. 6, most genes are interrupted or discontinued. 7, gene families and supergene families.,真核生物基因组结构特点,1，均为DNA， 体细胞基因组为二倍体。

2，基因数大，结构复杂，多复制起始点 3，转录产物为单顺反子，无操纵子结构 4，非编码序列占基因组的90%以上 5，有大量的重复序列 6，大多数基因是断裂基因 7，多基因家族，超基因家族某些生物的基因组数据物种 基因组大小 基因数目 基因长度ΦX174 0.7kb 10 λ嗜菌体 45Kb 100 大肠杆菌 4,7Mb 4200 1.2kb 酿酒酵母 13,5Mb 6300 1.4kb 果蝇 165Mb 12000 11.3kb 小鼠 3.3Gb ～30000 人 3.2Gb 35000 16.3kb 拟南芥 70Gb 25000,,,,Noncoding sequence (1) A large proportion of the DNA in eukaryotic cells does not code for protein; most genes have large intron sequences, and gene and gene clusters are separated by large stretches of sequence of unknown function.,(2) Much of this DNA consists of multiple repeats, sometimes thousands or hundreds of thousands of copies, of a few relatively short sequence elements.,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,Yeast (chromosome 3),Human β-globin gene cluster(chromosome 11),tRNA gene,,ORF,,ψβ2 ε Gγ Aγ ψβ1 δ β,Alu site,Diagrams of ～80kb region from yeast and human chromosomes,人类基因组人类单倍体基因组由24条染色体组成,共 3.2x109bp, 大约3.5万个基因。

人类染色体,1，重复序列 2，多基因家族 3，假基因 4，断裂基因 5，原癌基因 6，转座子 7，DNA多态性,1，重复序列(repeated sequances) 指在基因组中多次出现的DNA序列由特定长度的重复单位，特定的拷贝数目在空间上以特定的方式组成根据Cot曲线分为高度重复序列，中等重复序列和单拷贝序列Reassociation kineticsThis technique allows different classes of repeated DNA to be identified by the effect of multiple copies of a sequence on the rate of renaturation of denatured genomic DNA fragments.,By this method, human DNA can be classified into highly repeated DNA, moderately repetitive DNA and unique DNA.,,,,,,,,,,,,Fraction of reassociation,10-7 10-5 10-3 10-1 10 103 105,0,50,100,,human,E.coli,U:A(1bp),lg Cot 0.5,Cot curve,1-,Phage λ,,,,CC0,,重复序列的结构特定大小序列（重复单位），特定拷贝数, 在空间上以特殊方式组成。

正向重复,,,,,,,,,,,,AGGTAGGT TCCATCCA,AGGTNNNNAGGT TCCA NNNNTCCA,ACTT TTCA TGAAAAGT,ACTTNNNN TTCATGAANNNNAAGT,反向重复,串联,两侧对称,,,,,,,,,,,旋转对称,ACGGCCGT ACGGNNNNNCCGTTGCCGGCA TCCCNNNNNGGGA,(1) 高度重复序列 (high repetitive sequence) 重复次数>105，重复单位2～10 bp. 卫星 DNA (satellite DNA),集中在染色体的中心粒,Satellite DNAsatellite DNA consists of huge numbers of tandem repeats of short sequence, occurs mostly near the centromeres of chromosomes, and may be involved in attachment of the mitosis spindle.,（2）中等重复序列包括：A 编码序列，如RNA基因，组蛋白基因、免疫球蛋基因。

B，非编码序列，如Alu, KpnImodulate repetitive sequencesmuch of the moderately repeated sequence comprises a number of few hundred base pair, each repeated 103 to 106 times and scattered throughout the genome.,,人染色体的中等重复DNA家族,家族 长度（bp) 出现频率 占基因组的百分数 多聚(GT) ~40 130 000 0.2 K ~200 1 050 0.01O 375~435 4 500 0.07~0.08KpnI 670~6 400 5 000 1.0Alu 300 0,5~1×106 9,,,,人DNA 的Alu序列 170bp 130bp CTAGTGGGGA…GGGGA………… CTAGT 内部正向重复序列（40bp) Alu位点 侧翼正向重复序列（7-10bp),,,,,,,,,,,,,,,,,,,,Alu 在人类染色体的分布1号染色体 7号染色体 1和7号染色体 欧洲人和北美人 75% 50% 25% 亚洲人 60% 50% 10% 撒哈拉非洲人 95% 5%,,(3) 单拷贝序列（unique sequences) 在基因组中只出现一次或少数几次的序列.(unique sequences essentially comprises single-copy genes,or those repeated a few times).单拷贝序列中小部分编码蛋白质.,。