Einführung in die GenetikProf. Dr. Kay Schneitz (EBio Pflanzen)

http://plantdev.wzw.tum.dekay.schneitz@tum.deTwitter: @PlantDevTUM, #genetikTUMFB: Plant Development TUM

Prof. Dr. Claus Schwechheimer (PlaSysBiol)http://wzw.tum.de/sysbiolclaus.schwechheimer@wzw.tum.de

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