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Lecture 27. 第 10 章 重组 10.1 同源重组 10.1.1 交换机理 10.1.2 双链断裂 修复机理 10.1.3 RecBCD 途径 10.1.4 基因转换 10.2 非同源重组 10.2.1 转座子 10.2.2 反转录转座子 10.2.3 λ 噬菌体的整合. Chapter 10 Recombination 10.1 Homologous Recombination 10.1.1 Mechanism for Crossing-Over

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Lecture 27

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Lecture 27

Lecture 27

第10章 重组

10.1 同源重组

10.1.1 交换机理

10.1.2 双链断裂

修复机理

10.1.3 RecBCD途径

10.1.4 基因转换

10.2 非同源重组

10.2.1 转座子

10.2.2 反转录转座子

10.2.3 λ噬菌体的整合

Chapter 10 Recombination

10.1 Homologous Recombination

10.1.1 Mechanism for Crossing-Over

10.1.2 Mechanism for Double-

Stranded Break Repair

10.1.3 The RecBCD pathway

10.1.4 Gene Conversion

10.2 Non-homologous Recombination

10.2.1 Transposons

10.2.2 Retrotransposons

10.2.3 Bacteriophage λ integration


Review of lecture 26

Review of Lecture 26

A1→Homologous Recombination 同源重组

A2-1→ Resolution of the Holliday junction to create

a crossover产生交换的Holliday交叉拆分

A2-2→ Resolution of Holliday junctions for

non-crossover不产生交换的Holliday交叉拆分

A3→ The RecBCD Pathway / RecBCD途径


A1 homologous recombination

A1→Homologous Recombination 同源重组

同源重组:在具有相似DNA序列的DNA分子之间发生的重组。

Homologous recombination:Recombination between DNA molecules with similar DNA sequences.


A2 1 resolution of the holliday junction to create a crossover holliday

A2-1→ Resolution of the Holliday junctionto create a crossover产生交换的Holliday交叉拆分


A2 2 resolution of holliday junctions for non crossover holliday

A2-2→ Resolution of Holliday junctionsfor non-crossover不产生交换的Holliday交叉拆分


A3 the recbcd pathway recbcd

A3→ The RecBCD Pathway RecBCD途径

RecBCD途径:大肠杆菌中一种由RecBCD蛋白启动的主要的同源重组途径。

RecBCD pathway:The major homologous recombination

pathway in E. coli, initiated by the RecBCD protein.

RecBCD蛋白:大肠杆菌中能在DNA的χ位点产生切口的蛋白质。

RecBCD protein:The protein that nicks one of the DNA strands at a chi site to initiate homologous recombination in E. coli.


Questions for lecture 27

Questions for Lecture 27

Q1→ What is gene conversion?

什么是基因转换?

Q2→ What are transposons?

什么是转座子?

Q3→ What are retrotransposons?什么是反转录转座子?


Vocabulary of lecture 27 1 1

Vocabulary of Lecture 27 (1/1)

site-specific recombination

attachment site

integrase

excisionase

integration host factor, IHF

transposase

resolvase

replicative transposition

conservative transposition

staggered ends

direct repeat

retrotransposon

位点特异性重组

附着位点

整合酶

切除酶

整合宿主因子

转座酶

解离酶

复制型转座

保守型转座

交错末端

同向重复(序列)

反转录转座子


Q1 what is gene conversion

Q1→ What is gene conversion?什么是基因转换?


A1 10 1 4 gene conversion

A1→ 10.1.4 Gene Conversion / 基因转换

基因转换:同源重组的后果,在不同等位基因之间的杂交使其中的一个等位基因被转换成了另一个等位基因。这是由错配修复引起的。

Gene conversion:Consequence of homologous recombination, in which hybridization between different alleles causes one allele to be converted into the other. This occurs by mismatch repair.

等位基因:同一基因的不同版本,它们之间在功能和序列上稍有不同。

Alleles:Versions of the same gene that differ slightly in function and sequence.


Homologous n ot identical

Homologous, not identical同源的,而不是相同的

Homologous, not identical.

G

C

T

A

3’

5’

5’

3’

G

T

T

A

5’

3’

3’

5’

Chapter 10, page 225


Gene conversion

Gene Conversion / 基因转换

5’

3’

3’

5’

5’

3’

3’

5’

3’

5’

5’

3’

3’

5’

5’

3’


Neurospora crassa

Neurospora crassa 粗糙脉孢菌

+

+

4 : 4

+

+

+

+

+

+

+

+

m

m

m

m

m

m

m

m

m

Meiosis I

减数分裂I

Meiosis II

减数分裂II

m

Mitosis

有丝分裂


Neurospora crassa1

Neurospora crassa 粗糙脉孢菌

4 : 4

6 : 2

5 : 3

www.neurosporagenome.org/

www.nigms.nih.gov/Initiatives/Models/

www.neurosporagenome.org/


10 2 non homologous recombination

10.2 Non-homologous Recombination非同源重组

Non-homologous recombination:Rearrangement of DNA regions that are not similar (homologous) to each other.

非同源重组:互相不相似的(即不同源的)DNA区域之间的重排。

10.2.1 Transposons 转座子

10.2.2 Retrotransposons反转录转座子

10.2.3 Bacteriophage λ integration

λ噬菌体的整合


Q2 what are transposons

Q2→ What are transposons?什么是转座子?


A2 10 2 1 transposons

A2→ 10.2.1 Transposons / 转座子

转座子:基因组中能改变位置或位点的DNA元件。

Transposons:DNA elements that can change positions, or locations, in the genome.

插入序列:简单的原核生物转座子。它们是一些能使自身插入到一段DNA随机位置中的序列。

Insertion sequences:Simple prokaryotic transposons that insert themselves into random sites on a piece of DNA.


Complex transposons

Complex transposons / 复杂转座子

Inverted repeat orientation: e.g. Tn10

23 722 23 23 722 23

Antibiotic

resistance

IS1

IS1

Direct repeat orientation: e.g. Tn9

23 722 23 23 722 23

Antibiotic

resistance

IS1

IS1


More complex transposons

More complex transposons / 更复杂的转座子

tnpA tnpRbla

res

IR

IR

Transposase

转座酶

Resolvase

解离酶

β-lactamase

β内酰胺酶

(Ampr)

Organization of the Tn3 transposon

转座子Tn3的组成


Transposition

Transposition / 转座

What is the other name(s) for transposon?


Simplified mechanism of transposition

Simplified mechanism of transposition简化的转座机理


Direct repeats

Direct repeats / 同向重复序列

同向重复序列:完全相同并以相同方向出现的序列。

Direct repeats:Sequences that are exactly the same, and present in the same orientation.

反向重复序列:互补序列从反方向读与它自身相同的序列。

Inverted repeats:Sequences that are the same if you take the complement of one and read it backwards.


Replicative transposition

Replicative transposition / 复制型转座


Conservative transposition

Conservativetransposition / 保守型转座


Q3 what are retrotransposons

Q3→ What are retrotransposons?什么是反转录转座子?


A3 10 2 2 retrotransposon

A3→10.2.2 Retrotransposon反转录转座子

反转录转座子:一种以类似于反转录病毒机理进行转座的DNA 元件。

Retrotransposon:A transposable DNA element that transposes via a retrovirus-like mechanism.

反转录病毒:一种RNA病毒,其复制依赖于通过反转录形成的原病毒。

Retrovirus:An RNA virus whose replication depends on formation of a provirus by reverse transcription.

LTR-Retrotransposons LTR反转录转座子

Non-LTR retrotransposons 非LTR反转录转座子


Ltr retrotransposons ltr

LTR-Retrotransposons / LTR反转录转座子

长末端重复序列:在反转录病毒的原病毒两端发现的由几百个碱基对组成的DNA区域。

Long terminal repeats (LTRs) :Regions of several hundred base pairs of DNA found at both ends of the provirus of a retrovirus.


Non ltr retrotransposons ltr

Non-LTR retrotransposons非LTR反转录转座子

Weaver’s Molecular Biology, 3rd Edition, Figure 23.31


10 2 3 bacteriophage integration

10.2.3 Bacteriophage λ integrationλ噬菌体的整合

Lysogeny

Lysis


Phage integration and excision

Phage integration and excision

attP: attachment sites of phage

attB: attachment sites of bacterium


Now showing gene conversion

Now showingGene Conversion

File: biophoto7 \ Introduction to Genetic Analysis \

Genetic Consequences of Meselson-Radding Model


Gene conversion 1 5

Gene Conversion (1/5)

In this cross of + X m, the m site corresponds to a mutated nucleotide pair. If, by chance, m becomes part of a heteroduplex, the Meselson-Radding model predicts aberrant ratios of the + : m alleles.


Gene conversion 2 5

Gene Conversion (2/5)

In most cases, m will not be part of a heteroduplex, so two of the four meiotic products will carry the mutation. After one round of mitosis, the resulting octad (八联体)has a 4:4 ratio of + : m.


Gene conversion 3 5

Gene Conversion (3/5)

At low frequency, an asymmetric heteroduplex including the m site can be generated by strand invasion, as postulated by the Meselson-Radding model. A crossover event without branch migration generates one +/m heteroduplex.


Gene conversion 4 5

Gene Conversion (4/5)

If the +/m mismatched base pair is not repaired, a 5:3 octad ratio is produced.


Gene conversion 5 5

Gene Conversion (5/5)

If the m strand of the mismatched DNA is repaired to +, a 6:2 octad ratio results.


Now showing again

Now showing again


Now showing replicative transposition

Now showingReplicative transposition

File: biophoto7 \Introduction to Genetic Analysis

\ Replicative transposition. (5’)


Replicative transposition 1 9

Replicative transposition (1/9)

Transposition is the movement of genetic elements, called transposons, between plasmids or genomes.


Replicative transposition 2 9

Replicative transposition (2/9)

Shown here is a mechanism of replicative trans-position by the E. coli Tn3 transposon. A copy of Tn3 will be generated in the target plasmid.


Replicative transposition 3 9

Replicative transposition (3/9)

The transposon is flanked by inverted repeat sequences and consists of several genes. One of these genes encodes the transposase enzyme.


Replicative transposition 4 9

Replicative transposition (4/9)

In the target plasmid, transposase acts at the region of insertion.


Replicative transposition 5 9

Replicative transposition (5/9)

The target plasmid is cleaved by transposase to yield staggered ends nine nucleotides apart.


Replicative transposition 6 9

Replicative transposition (6/9)

Transposase also cleaves the plasmid containing the transposon at the ends of the transposable element. These ends are joined with the ends of the target plasmid.


Replicative transposition 7 9

Replicative transposition (7/9)

The single-stranded regions of DNA are replicated.


Replicative transposition 8 9

Replicative transposition (8/9)

The resulting plasmid is called a cointegrate(共整合体). It contains the original transposon and a new copy.


Replicative transposition 9 9

Replicative transposition (9/9)

The cointegrate is resolved into the original plasmid and the target plasmid by an enzyme called resolvase. The transposon contains a sequence called the internal resolution site, or IRS, which is necessary for resolution.


Now showing again1

Now showing again


Essentials of lecture 27 27

Essentials of Lecture 27 / 第27讲要点

A1→ Gene Conversion / 基因转换

A2→ Transposons / 转座子

A3→ Retrotransposon / 反转录转座子


A1 10 1 4 gene conversion1

A1→ 10.1.4 Gene Conversion / 基因转换

基因转换:同源重组的后果,在不同等位基因之间的杂交使其中的一个等位基因被转换成了另一个等位基因。这是由错配修复引起的。

Gene conversion:Consequence of homologous recombination, in which hybridization between different alleles causes one allele to be converted into the other. This occurs by mismatch repair.

等位基因:同一基因的不同版本,它们之间在功能和序列上稍有不同。

Alleles:Versions of the same gene that differ slightly in function and sequence.


A2 10 2 1 transposons1

A2→ 10.2.1 Transposons / 转座子

转座子:基因组中能改变位置或位点的DNA元件。

Transposons:DNA elements that can change positions, or locations, in the genome.

插入序列:简单的原核生物转座子。它们是一些能使自身插入到一段DNA随机位置中的序列。

Insertion sequences:Simple prokaryotic transposons that insert themselves into random sites on a piece of DNA.


A3 10 2 2 retrotransposon1

A3→10.2.2 Retrotransposon反转录转座子

反转录转座子:一种以类似于反转录病毒机理进行转座的DNA 元件。

Retrotransposon:A transposable DNA element that transposes via a retrovirus-like mechanism.

反转录病毒:一种RNA病毒,其复制依赖于通过反转录形成的原病毒。

Retrovirus:An RNA virus whose replication depends on formation of a provirus by reverse transcription.

LTR-Retrotransposons LTR反转录转座子

Non-LTR retrotransposons 非LTR反转录转座子


Lecture 28

Lecture 28

附录D

实验技术

D.1 DNA操作技术

D.2 操作蛋白质

D.3 基因及其

蛋白质的功能

Appendix D

Experimental Techniques

D.1 DNA manipulation

techniques

D.2 Manipulating Proteins

D.3 The Function of Genes

and their Proteins


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