![Page 1: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/1.jpg)
II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS
![Page 2: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/2.jpg)
Structure of a „typical” animal cell
![Page 3: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/3.jpg)
Structure of a „typical” plant cell
![Page 4: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/4.jpg)
II.1.4. Nucleus
Biological significance: storage, expression and transmission of the genetic information.
![Page 5: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/5.jpg)
Segmented nuclei of leukocytesSegmented nuclei of leukocytes
neutrophils
![Page 6: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/6.jpg)
Structural components
![Page 7: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/7.jpg)
II.1.4.1. Nuclear membrane (envelope)
cytoplasm
nuclear membrane nuclear lamina
chromatin
nuclear pore
Biological significance: limiting layer between the inner part of the nucleus and the cytoplasm. Specific transport of micro- and macromolecules.
![Page 8: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/8.jpg)
The nuclear envelopenuclear envelope is formed from two concentric membranes that are continuous with the endoplasmic reticulum (ER). The space between the two membranes is the perinuclear spaceperinuclear space which is continuous with the lumen of the ER.
The inner nuclear membrane contains proteins which enable it to bind to the nuclear laminanuclear lamina (network of intermediate filaments), which binds the chromatin.
The double-membrane envelope is penetrated by nuclear poresnuclear pores.
![Page 9: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/9.jpg)
Nuclear pore
EM imageConstruction
surface wiev
side wiev
![Page 10: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/10.jpg)
Relationship of the nucleus and the cytosol
![Page 11: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/11.jpg)
II.1.4.2. Chromatin
The chromatin is composed of deoxyribonucleic acids and proteins. In interphase they are arranged in a relatively loose , „network” form. EM shows that there are two different forms of the chromatin, one appearing as a light element (euchromatin), the other one being dark (heterochromatin).
HeterochromatinHeterochromatin: Closely packed chromatin . The DNA is organized by histon and non-histone proteins.
Euchromatin:Euchromatin:
Here the chromatin is loosely arranged. The DNA double helices are partially split to single strands by RNA polymerases.
![Page 12: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/12.jpg)
Euchromatic nucleus of neuronEuchromatic nucleus of neuron
![Page 13: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/13.jpg)
H2A, H2B, H3 and H4 (two molecules of each) are building the Histone-Octamer . The DNA double helix makes two turns around this octamer (166 base pairs). H1 binds to theis complex.
(packing level: 6-7x) H1
Octamer
1. Level of organisation: NucleosomeNucleosome
Structure
The chromatin is a DNA-protein complex About half of the chromatin is protein: they are either histones or non-histone proteins.
Histones Histones are small, positively charged proteins, which bind non-specifically to DNA end compensate the negative charge of phosphate groups of the DNA.
Histone classes: H1, H2A, H2B, H3 and H4.
![Page 14: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/14.jpg)
2. Level of organisation : 30 nm chromatin fiber30 nm chromatin fiber
The nucleosomes are spirally organized around the H1 core (packing level: ~ 40 x)
This structure is broken to segments by binding of non-histone proteins (e.g. gene regulator proteins).
![Page 15: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/15.jpg)
3. Level of organisation: 300 nm chromatin fibers300 nm chromatin fibers
30 nm chromatin fiber
loop domains
20 000-30 000 base pairs
300
nm
![Page 16: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/16.jpg)
Chromosomes
W. Waldeyer, 1888:
" …thick chromatin structures which can be seen during mitosis and meiosis...„
Name: chroma: color and soma: body
Boveri and Sutton, 1905. Chromosome theory: the chromoses are the carriers of the genetic information..
Chromosomes exists only during cell division as microscopically Chromosomes exists only during cell division as microscopically detecteble units. detecteble units.
At the start of the mitosis (M phase) each chromose has replicated and consists of two sister chromatids joined together
![Page 17: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/17.jpg)
Fine structure
Chromatids: 300 nm chromatin fiber form spirals (packing level: 10 000 x)
300 nm
700 nm
![Page 18: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/18.jpg)
Staining of the chromosomes
• Fluorescent stains (e.g. Quinacrin): Q-Q-bands bands specific for AT-rich DNA regions
• Giemsa-staining:according to the technique applied, either G-bandsG-bands ("Giemsa-positiv")
specific for AT-rich DNA-regions or
R-bandsR-bands ("Giemsa-negativ")
specific for GC-rich DNA-regions
![Page 19: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/19.jpg)
ChromosomesThe human karyotype
![Page 20: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/20.jpg)
fruitfly 8 house fly 12 ant 48 frog 26 carp 104 dog 38 cat 64 mouse
40 rat42
cattle 60 rhesus monkey 42 human 46
baker’s yeast 32 corn
20 rice 24 wheat
42 tobacco 48
Chromosomal organization of different species
![Page 21: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/21.jpg)
Variability in chromosomal organization.
Chromosomal organization (karyotype) can show high variability even in closely related species.
The number of genes is equal!
Reeves deer
Indian deer
![Page 22: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/22.jpg)
Scanning-EM, human
chromosomes
Schematic view of
chromosomal regions
X 4 5
Tel omer
shorter arm „p”
longer arm „q”
centromer1
23
45
1
1 1
111
2
2
2 233
sister chromatids
Structure of the chromosomes
![Page 23: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/23.jpg)
Telomers, aging, cancer (and Dolly)
Human telomer: 15 000 base pairs of repeated TTAGGG DNA sequences. Shortening: 50-200 base pairs/division.
In germline cells: telomere terminal transferase (telomerase): ribonucleoprotein reverse transcriptase.
![Page 24: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/24.jpg)
Binding of the chromosomes to the mitotic spindle
Attachment site:
kinetochorkinetochor at the centromer
![Page 25: II. INTERNAL ORGANIZATION OF EUKARYOTIC CELLS. Structure of a „typical” animal cell](https://reader035.vdocuments.net/reader035/viewer/2022062321/56649dea5503460f94ae55e5/html5/thumbnails/25.jpg)
Preparation of chromosomes, karyotype determination
Blood culture (phytohaemagglutinin) colchicin separation of erythrocytes and white blood cells fixation staining
microphotoarrange according to size, centromer position and banding pattern