Einführung in die Genetik Prof. Dr. Kay Schneitz (EBio Pflanzen) http://plantdev.bio.wzw.tum.de schneitz@wzw.tum.de Prof. Dr. Claus Schwechheimer (PlaSysBiol) http://wzw.tum.de/sysbiol claus.schwechheimer@wzw.tum.de
Einführung in die Genetik - Inhalte 1 Einführung 16. 10. 12 KS 2 Struktur von Genen und Chromosomen 23. 10. 12 KS 3 Genfunktion 30. 10. 12 KS 4 Transmission der DNA während der Zellteilung 06. 11. 12 KS 5 Vererbung von Einzelgenveränderungen 13. 11. 12 KS 6 Genetische Rekombination (Eukaryonten) 20. 11. 12 KS 7 Genetische Rekombination (Bakterien/Viren) 27. 11. 12 KS 8 Rekombinante DNA-Technologie 04. 12. 12 CS 9 Kartierung/Charakterisierung ganzer Genome 11. 12. 12 CS 10 Genmutationen: Ursache und Reparatur 18. 12. 12 CS 11 Veränderungen der Chromosomen 08. 01. 13 CS 12 Genetische Analyse biologischer Prozesse 15. 01. 13 CS 13 Transposons bei Eukaryonten 22. 01. 13 CS 14 Regulation der Genexpression 29. 01. 13 KS 15 Regulation der Zellzahl - Onkogene 05. 02. 13 CS
Chromosome mutations Genetics 11 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 analysis Genetics 12 Based on Chapter 4 (9th or10th ed.)
Model organisms Arabidopsis Drosophila WT agamous WT antennapedia
Mutational analysis Recombination and linkage Phenotypic markers Molecular markers Insertional mutagenesis and reverse genetics
Mutational analysis
Mutational analysis and model organisms Arabidopsis Drosophila WT agamous WT antennapedia
Gene discovery through mutational analysis
Spontaneous and induced mutations 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
Types of mutations Loss-of-function Gain-of-function null or amorphic leaky or hypomorphic recessive hypermorphic neomorphic dominant haploinsufficiency (semi-)dominant
Genetic selection vs. genetic screen
Dominance/recessivity
Dominance/recessivity
Recombination and linkage
Linkage: linked alleles are inherited together Figure 4-2 vestigial, vg wild type purple
Crossing over: produces new allelic combinations Figure 4-3
Crossing over: recombination of genetic material Red: Bivalent paired chromosomes Blue: Centromer Green: Chiasmata
Crossing over is between chromatids, not chromosomes Wrong! Figure 4-5 Correct!
Multiple crossovers can include more than two chromatids Figure 4-6
Recombinants are produced by crossovers Figure 4-7
For linked genes, recombinant frequencies are less than 50 percent Figure 4-8
Nomenclature Cis Trans AB/ab or ++/ab Ab/aB or +b/a+ Loci on the same chromosome AB/AB Loci 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 b c RF = Nrec Total x 100 1% = 1 map unit (m.u.) = 1 cm (centimorgan) cm gives a rough idea of the distance between two loci
Map distances are generally additive Figure 4-9
Example: Mapping of the BRI1 gene Marker Marker Marker Marker Marker
Longer regions have more crossovers and thus higher recombinant frequencies
Phenotypic markers
Phenotypic markers of pea
Phenotypic markers on the tomato chromosomes Figure 4-13c
Molecular markers
Simple Sequence Length Polymorphisms (SSLPs) - microsatellite markers - Figure 4-19a
Simple Sequence Length Polymorphisms (SSLPs) - minisatellite markers - Figure 4-18
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)
Restriction fragment length polymorphism (RFLP) Figure 4-15a
Restriction Fragment Length Polymorphism (RFLP) Figure 4-15b
Restriction fragment length polymorphism (RFLP) Figure 4-15c
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)
Haplotypes and Single Nucleotide Polymorphisms (SNPs) Figure 4-16
Phenotypic and molecular markers mapped on human chromosome 1 Figure 4-20
Alignment of physical and recombination maps Figure 4-25
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
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