Organisation of the genetic material in pro- and eukariotic cells DNA, chromatin, chromosomes.

Organisation of the genetic material in pro- and eukariotic cells

DNA, chromatin, chromosomes

1 µm = 2 Megadalton (2 x 106 Dalton) = 3 kbp

Genome ContentGenome Content

Human Genome3200 Mb

Genes and gene-related sequences 1200Mb

Intergenic DNA2000 Mb

Genes48 Mb

Related seq.1152 Mb

PseudogenesGene fragmentsIntrons, UTRs

Interspersed repeats1400 Mb

Other intergenic

regions600 Mb

Microsatellites90 Mb

Various510 Mb

LINES640 Mb

SINES420 Mb

LTR elements250 Mb

DNA transposons90 Mb

SINE: Alu, 281 bp, 300.000 p, 9%

LINE: L1, 6500 bp, 50.000 p, 7%, retrotransposon

T phage ofEsherichia coli~ 50 m DNA.

Single Circular DNA molecule of Escherichia coli, ~1,4 mm long

~4 cm linear DNA molecule contains in a usual human chromosome

E. coli: 4 639 221 nukleotide pairs, 4200 genes

Relaxed

Supercoiled

Topoisomerases

Nucleus of a eukariotic cells (electronmicrograph)Function: protection, transport,gene expression

nuclear lamina

HETEROCHROMATIN

euchromatin

heterochromatin

nucleolus

1 µm = 2 Megadalton (2 x 106 Dalton) = 3 kbp

Types of the chromatin: eu- and

heterochromatin

Structure of the chromatin ;

histons, nucleosomes, solenoid and loops

Histones:

small, basic, higly conserved proteins

30 nm chromatin fiber:interactions and modifications of site chains of histones and H1 histon are necessary

The sructure of the 30 nmchromatin fiber is variable(heterogen)

11 and 30 nm chromatin fibers (electonmicrograph)

„beads-on-a-string” structure

solenoid

H2AH2BH3H4

• Chromatin structure and gene expresson in that area are hang on the chemical modification of histones (acetylations, metylation, phosphorylation)

Condensins organise the loop-structure

SMC = Structural Maintenance of Chromosomes family protein (part of the condensin complex)

DNA

Chromatin

Loops

Metaphase chromosome

Chemical modification of the DNA (methylation) has role in regulation

de novo metylases

Imprinting

XIST = X inactivaton specific transcript

XIC = X inactivation center

Histones also play role in the inactivation

Localization of the chromosome 18 and chr. 19 in interphase nucleus

The chromosome structure and the cell divisionArms, centromer, telomers

arms sisterchromatides

Kinetochor microtubuls

Lewin: Genes IX. Fig. 28.30

Telomer and telomerase

fibrillar

granular

light stained

A magvacskafunkciói

Special chromosomes

Politen chromosome – in salivary

glands of Drosophila

melanogaster

Lampbrush chromosomes –

amphybian

oocytes

Politenchromosomes

RNA synthesis on the politenchromosomes

Lampbrush chromosomes in an amphybian oocyte