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
polymorphi
sm
Differences in
performance on
the DNA fragment
length
DNA
Sequence
polymorphis
m
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
Repeatin
g units
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 15-30bp，
序列总长度约100bp-20kb
基因座A(VNTR)
微卫星DNA (microstatellite
DNA)
基因座B(STR)
Repeat unit length26bp，Repeat the number
10 to 60 times，Sequence
length under 400 bp，又称
短串联重复序列（short
（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 length6-70bp，
基因座A(VNTR)
After several repetitions hundreds of timesAbout 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,
基因座B(STR)
Repeat number 10 to 60
times,
Sequence length under 400
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
PLA2A ：[ATT]8-17
Some loci in the core of the individual genes
sequence have tiny difference：
TH01：[AATG]5-11
Length of 173 bp of alleles：
[AATG]4ATG[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.
GABRB15：[GATA]5-12[GATC]2-4[TATC]1-2
TFIIDA：
[CAG]3[CAA]3[CAG]9-11CAA[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.
D21S11：
TCTA/TCTG, 172-264bp
Of three variable and a constant
D21S11： TCTA/TCTG, 172-264bp;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
TH01：[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. HumTH01
♦Non-coding regions/positioning STR loci
-- - the place was named after the location
of the chromosome
D16S539:
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
TH01：[AATG]9
Repetitions for 9, the allele named 9
♦Allele containing incomplete repeat unit
(complete repetitions) (don't repeat the base
number)
TH01 length of 173 bp alleles in:
[AATG]4ATG[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
HollidayGenetic 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
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 0.1-30kb
length
of
the
sequence
400bp以下
Repeat unit 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
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 are 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 4th generation sign:?