einführung in die genetik - developmental...
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Einführung in die GenetikProf. Dr. Kay Schneitz (EBio Pflanzen)
http://[email protected]: @PlantDevTUM, #genetikTUMFB: Plant Development TUM
Prof. Dr. Claus Schwechheimer (PlaSysBiol)http://wzw.tum.de/[email protected]
Einführung in die Genetik - Inhalte1 Einführung 07. 10. 14 KS
2 Struktur von Genen und Chromosomen 14. 10. 14 KS
3 Genfunktion 21. 10. 14 KS
4 Transmission der DNA während der Zellteilung 28. 10. 14 KS
5 Vererbung von Einzelgenveränderungen 04. 11. 14 KS
6 Genetische Rekombination (Eukaryonten) 11. 11. 14 KS
7 Genetische Rekombination (Bakterien/Viren) 18. 11. 14 KS
8 Rekombinante DNA-Technologie 25. 11. 14 CS
9 Kartierung/Charakterisierung ganzer Genome 02. 12. 14 CS
10 Genmutationen: Ursache und Reparatur 09. 12. 14 CS
11 Regulation der Genexpression 16. 12. 14 KS
12 Veränderungen der Chromosomen 23. 12. 14 CS
13 Genetische Analyse biologischer Prozesse 13. 01. 15 CS
14 Transposons bei Eukaryonten 20. 01. 15 CS
15 Regulation der Zellzahl - Onkogene 27. 01. 15 CS
Chromosome mutationsGenetics 12
Based on Chapter 16 (Griffiths; 9th ed.); Chapter 7 (10th ed.)
Summary • Euploidy and polyploidy
• crop plants, brassica, wheat, breeding
• colchicin
• triploids, tetraploids
• autopolyploids, allopolyploids, bastards
• Aneuploidy
• Meiotic nondisjunction
• Turner syndrome
• Klinefelter syndrome
• Down syndrome
• Changes in chromosome structure
• DNA double strand breaks
• Cross over and repetitive elements
• Deletion (pseudodominance)
• Inversion (paracentric, pericentric)
• Duplication
• Translocations (Robertson’s translocations)
• Chromosomal mutations and disease
• Burkitt lymphoma (Reg(IG) -> MYC)
• Chronic myelogenous leukemia (ABL:BCR1)
Genetic analysisGenetics 13
Based on Chapter 4 (9th or10th ed.)
Model organisms
WT agamous WT antennapedia
Arabidopsis Drosophila
Recombination and linkage
Phenotypic markers
Molecular markers
Mutational analysis
Insertional mutagenesis and reverse genetics
Mutational analysis
Mutational analysis and model organisms
WT agamous WT antennapedia
Arabidopsis Drosophila
Gene discovery through mutational analysis
Types of mutagens
• Base-substitution mutagens – high rates of transitions – alkylating agents best in some systems – base analogs best in some systems
• Indel mutagens – insertion/deletion of single base pairs – proflavin, quinacrine mustards
• Insertional mutagens – transposable elements (natural and
engineered) • Chromosomal rearrangement mutagens
– deletions, duplications, inversions, translocations
– formaldehyde, X-rays, transposable elements
Spontaneous and induced mutations
Types of mutations
Loss-of-function Gain-of-function
null or amorphic
leaky or hypomorphic neomorphic
hypermorphic
recessive dominant
haploinsufficiency
(semi-)dominant
Genetic selection vs. genetic screen
Dominance/recessivity
Dominance/recessivity
Recombination and linkage
Figure 4-2
Linkage: linked alleles are inherited together
vestigial, vg wild type
purple
Figure 4-3
Crossing over: produces new allelic combinations
Crossing over: recombination of genetic material
Red: Bivalent paired chromosomesBlue: CentromerGreen: Chiasmata
Figure 4-5
Crossing over is between chromatids, not chromosomes
Wrong!
Correct!
Figure 4-6
Multiple crossovers can include morethan two chromatids
Figure 4-7
Recombinants are produced by crossovers
Figure 4-8
For linked genes, recombinant frequencies areless than 50 percent
Nomenclature
Cis AB/ab or ++/abTrans Ab/aB or +b/a+
Loci on the same chromosome AB/ABLoci on different chromosomes AB/AB ; CD/CD
Linkage
• When two genes/loci are close together on the same chromosome pair (they are linked), they do not assort independently but produce a recombinant frequency of less than 50 %
• Conversely, a recombination frequency of less than 50% is indicative for linkage
• Quantitating linkage is the basis of gene mapping
Calculating the recombinant frequency (RF)
a
RF =Nrec
Totalx 100
1% = 1 map unit (m.u.) = 1 cM (centiMorgan)cM gives a rough idea of the distance between two loci
b c
Figure 4-9
Map distances are generally additive
Longer regions have more crossovers and thus higher recombinant frequencies
Phenotypic markers
Phenotypic markers of pea
Figure 4-13c
Phenotypic markers on the tomato chromosomes
Molecular markers
Figure 4-19a
Simple Sequence Length Polymorphisms (SSLPs)- microsatellite markers -
Figure 4-18
Simple Sequence Length Polymorphisms (SSLPs)- minisatellite markers -
Single nucleotide polymorphisms (SNPs)- in humans one SNP every 300-1000 bp -
...AAGGCTCAT...
...TTCCGAGTA.....AAAGCTCAT......TTTCGAGTA...
• SNP can be within genes but the sequence change does not lead to a phenotype;
• SNP can be within an intergenic region and not cause a phenotype;
• SNP can be within a gene, alter its function and lead to a single inheritence phenotype;
• SNP can, together with other genes, be responsible for a polygenic trait;
• SNP can lead to the creation or deletion of a target site for restriction enzymes and the two
alleles can be examined as a restriction fragment length polymorphism (RFLP)
Figure 4-15a
Restriction fragment length polymorphism (RFLP)
Figure 4-15b
Restriction Fragment Length Polymorphism (RFLP)
Figure 4-15c
Restriction fragment length polymorphism (RFLP)
Single nucleotide polymorphisms (SNPs)- in humans one SNP every 300-1000 bp -
...AAGGCTCAT...
...TTCCGAGTA.....AAAGCTCAT......TTTCGAGTA...
• SNP can be within genes but the sequence change does not lead to a phenotype;
• SNP can be within an intergenic region and not cause a phenotype;
• SNP can be within a gene, alter its function and lead to a single inheritence phenotype;
• SNP can, together with other genes, be responsible for a polygenic trait;
• SNP can lead to the creation or deletion of a target site for restriction enzymes and the two
alleles can be examined as a restriction fragment length polymorphism (RFLP)
Figure 4-16
Haplotypes and Single Nucleotide Polymorphisms (SNPs)
Figure 4-20
Phenotypic and molecular markers mapped onhuman chromosome 1
Figure 4-25
Alignment of physical and recombination maps
Insertional mutagenesis and reverse genetics
Gene discovery through mutational analysis
Targeted gene knockouts
Targeted gene knockouts
Insertional mutagenesis in the mouse Mus musculus- gene targeting -
Stable plant transformation produces random insertions
Insertional mutagenesis with T-DNA
What you need to know and understand for
the exam and for your life....
... genetic selection vs. genetic screen
... use of mutagens in this context
... types of mutations (gain-of-function, loss-of-function;
morph nomenclature)
... calculation of recombination frequencies
... molecular markers (SNPs, RFLP, microsatellites)
... types of insertional mutagenesis
The end