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许冰莹, Tel: 0871 -65922837； 13769175605 Email: bingying_xu@126. com 昆明医科大学法医学院

第四节 DNA多态性 （DNA polymorphisms）

People on average on the DNA sequence of hundreds of bases can appear some variation (variation)，When these mutations in the form of alleles were preserved in the group，And when can be inherited from either parent to offspring，Can form the genetic differences between individuals。 The genetic differences between different individuals show the different alleles. In genomic DNA, formed by the different base structure of the allelic polymorphism called DNA polymorphism of DNA polymorphisms

DNA polymorphism DNA Length polymorphism Differences in performance on the DNA fragment length DNA Sequence polymorphism Differences in performance on the DNA base sequence

一、DNA长度多态性 (DNA length polymorphism) The same loci in the composition of the DNA fragment length difference between alleles polymorphism. The length of the differences between two fixed endpoints Repeatin g units

可变数目串联重复序列 Variable number tandem repeats, VNTRs 小卫星DNA (ministatellite DNA) 重复单位长度 15 -30 bp， 序列总长度约 100 bp-20 kb 基因座A(VNTR) 基因座B(STR) 微卫星DNA (microstatellite DNA) Repeat unit length 2 -6 bp， Repeat the number 10 to 60 times，Sequence length under 400 bp，又称短串联重 复序列（short tandem repeats, STRs）

（一）VNTR The sequence Consist of a short, base relatively conservative sequence as a repeating unit, Specific location in the genome tandem repeats, the formation of a sequence. 小卫星序列 (ministatellite sequence) Repeat unit length 6 -70 bp， 基因座A(VNTR) After several repetitions hundreds of times. About 100 bp sequence length - 20 KB

（二）STRThe sequence 短串联重复序列（short tandem repeats，STRs） 简单串联重复序列（simple tandem repeats，STRs ） 微卫星DNA (microstatellite DNA) Repeat unit length 2 -6 bp, Repeat number 10 to 60 times, 基因座B(STR) Sequence length under 400 bp

Widely distributed, 5% of the human genome, estimated that 20 -500000 The numerous genetic markers found more than 8000 Most distribution non-coding regions, rarely three nucleotides coding area Is the most common dinucleotide, forensic commonly used is repeated under the four nucleotides 基序（motif）：Base form of the repeat units。 FES/FPS：[ATTT]8 -14

1、STR The type of sequence structure （1）简单序列（simple repeats） Repeat the unit length and unit base composition. Basically the same motif：FES/FPS：[ATTT]8 -14 PLA 2 A ：[ATT]8 -17 Some loci in the core of the individual genes sequence have tiny difference： TH 01：[AATG]5 -11 Length of 173 bp of alleles： [AATG]4 ATG[AATG]5

（2）复合序列（compound repeats） The same loci alleles of the repeating unit is composed of two or more than two motif, but the length of the repeating units are basically identical. GABRB 15：[GATA]5 -12[GATC]2 -4[TATC]1 -2 TFIIDA： [CAG]3[CAA]3[CAG]9 -11 CAA[CAGCAA]0 -1[CAG]9 -24[CAA]2

（3）复杂重复序列（complex repeats） The same loci alleles between repeating unit base sequence differences, and repeat the unit length difference. D 21 S 11： TCTA/TCTG, 172 -264 bp Of three variable and a constant

D 21 S 11： TCTA/TCTG, 172 -264 bp; Of three variable and a constant

2、The naming of the STR （1）、 The naming of loci ♦Structural gene introns STR loci in: - named after gene name TH 01：[AATG]5 -11 Located on chromosome 11 tyrosine hydroxylase gene TH represents tyrosine hydroxylase 01 to the first intron loci locate Sometimes loci name prior to add a prefix Hum, said from the human genome: e. g. Hum. TH 01

♦Non-coding regions/positioning STR loci -- - the place was named after the location of the chromosome D 16 S 539: D - DNA 16 - on chromosome 16 S - single copy In the 539 - Genome Database storage data sequence number 539

（2）、 allele ♦According to the number of repeat units TH 01：[AATG]9 Repetitions for 9, the allele named 9 ♦Allele containing incomplete repeat unit (complete repetitions) (don't repeat the base number) TH 01 length of 173 bp alleles in: [AATG]4 ATG[AATG]5 ，The gene named 9. 3

3、Screening of STR loci Basic conditions: high degree of polymorphism and augmentation stability is good 1. Length of allele < 300 bp 2. Repeat units of 4 nucleotide, nothing but repeat unit base 3. The number of alleles. 8 -12 4. Loci heterozygosity > 0. 8, personal identification ability > 0. 9 5. Compare the average gene frequency distribution 6. The PCR amplification is stable, the mutation rate is low

4、Formation mechanism of length polymorphism （1）、he main reason for the duplicate slide: STR polymorphisms

（2）、The main cause of homologous recombination, VNTR polymorphisms Exchange areas of DNA nucleotide sequences of the same or similar Exchange links between complementary base

Holliday. Genetic recombination model

（3）、Alleles of structural rearrangement: The main reason for the small satellite DNA polymorphism

Small satellite DNA, microsatellite DNA and distinction Small satellite microsatellite DNA There is place Repeat unit length repetitions 染 色 体 近 端 粒 和 着 染色体任何部位 丝粒区 6 -70 bp 2 -6 bp 几次到几百次 10 -60次 The total 0. 1 -30 kb length of the sequence Repeat unit 400 bp以下 单位组成稍有差异， 重复单位的变异性低，

二、DNA序列多态性 （DNA sequence polymorphism） DNA sequence length are equal, but individual differences between the bases. A G C T C A G T T C A A A T

单核苷酸多态性 （Single nucleotide polymorphism, SNP） By a single nucleotide substitution, insertion or deletion of molecular polymorphisms. Show the second-class forms of a gene: mutation or normal At least one of the alleles form, the distribution frequency of not less than 1% in a group There at least 3 million SNPS in the human genome Point mutations

DNA遗传标记 Tags: 1 generation RFLP The second generation sign: VNTR, STR Third-generation tags: SNP The 4 th generation sign: ?