Organization of genetic material in eukaryotes

Transcription

1 Organization of genetic material in eukaryotes biologiemoleculara.usmf.md pass.: bmgu e.usmf.md 1 DNA in eukaryotes Location: In nucleus In mitochondria biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 2 DNA in eukaryotes Nuclear DNA: Long, linear molecules; Chromatin chromosomes; 10% of DNA in genes, 90% - non-coding; Gene activity depends on: Ontogenetic period; Type of cell; Environment biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 3 1

2 Nuclear envelope: Inner membrane Outer membrane Nuclear lamina Nuclear pore complex Chromatin Euchromatin Heterochromatin Nucleoli Nucleus Karyoplasm Nuclear skeleton biologiemoleculara.usmf.md Nuclear juice e.usmf.md pass.: bmgu 4 biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 5 Nucleus Functions: Contains ~ 98% of DNA; Assures functional packing of DNA: euchromatin active DNA; heterochromatin inactive DNA. Differential control of gene expression: Transcription and processing of RNA; Control of cell division: Replication of DNA and mitosis Biogenesis of ribososmes biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 6 2

3 biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 7 biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 8 biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 9 3

4 Import (cytoplasm to nucleus): Nuclear pores biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 10 Transport through nuclear pores mediated by karyopherins = importins and exportins Histones Non-histones dntp, NTP Ribosomal proteins mrna trna scrna RNP 40S; RNP 60S Export (nucleus to cytoplasm): biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 11 biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 12 4

5 CHROMATIN prophase telophase CHROMOSOME Chromatin genetic material (DNA) with different levels of packing during interphase; Chromosome genetic material at the highest level of packing during cell division. Chemical organization: 30% DNA + 40% histones + 25% nonhistones + 5% RNA biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 13 biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 14 Globular proteins Histones Basic proteins, rich in Liz and Arg; 5 types: H1, H2A, H2B, H3, H4 Function: DNA packing at first levels Non-specific control of gene expression Type of histone Basic amino acids No. of amino acids Shape of proteine H1 Liz 215 NH 2 COOH H2A Leu, Liz 129 NH 2 COOH H2B Ser, Pro, Liz 125 NH 2 COOH H3 Arg, Cis 135 NH 2 COOH H4 Arg, Liz 102 NH 2 COOH biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 15 5

6 Histones DNA + histones= nucleosome a. Histone core: Octamere 2H 2 A 2H 2 B 2H 3 2H 4 b. 200 b.p. Nucleosomal DNA c. H1 stabilizes DNP complex biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 16 biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 17 biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 18 6

7 biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 19 Non-histones Heterogeneous proteins; Nuclear enzymes for: replication; repair; transcription; processing of RNA; biogenesis of ribosomes Site specific proteins; Proteins of chromosomal scaffold biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 20 biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 21 7

8 Nucleus at different stages of cell cycle biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 22 Chromosomal RNAs Primary transcripts microrna parts of nuclear enzymes. biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 23 Levels of packing of nuclear DNA I st level nucleosome = 10 nm chromatin fiber; II nd level solenoid = 30 nm chromatin fiber; III rd level loops IV th level metaphase chromosome biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 24 8

9 biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 25 biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 26 I st level - nucleosome: 11 nm polynucleosome filament; x 6 condensation; Mechanism: DNA - interacts with basic proteins + Transcription is possible. biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 27 9

10 2 nd level solenoid 30 nm chromatin fiber; x 40 condensation; Mechanism: Phosphorilation of H1 folding of polynucleosome fiber 6 nucleosomes per tour; Transcription - blocked. biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 28 Solenoid biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 29 biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 30 10

11 3 rd level loops Large or small loops, 300nm; x condensation; Mechanism: 30 nm fiber attaches to scaffold; interaction between SAR (MAR) and scaffold Transcription - blocked biologiemoleculara.usmf.md e.usmf.md pass.: bmgu nm loops Scaffold biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 32!!! SAR (MAR) - (Scaffold /Matrix Associated Region) specific sites in DNA responsible for binding to scaffold;!!! scaffold interacts with: - chromatin; - lamins / proteins attached to nuclear envelope. biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 33 11

12 DNA Nucleosomes Scaffold Solenoid biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 34 biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 35 4 th level metaphase chromosome The highest level of condensation x10000; Chromatid ~700nm; mechanism: Pfosphorilation of lamins dissociation of nuclear envelope; Total phosphorilation of H1 condensation of chromatin, loops are folded around scaffold. biologiemoleculara.usmf.md Transcription blocked e.usmf.md pass.: bmgu 36 12

13 2 nm 11 nm 30 nm 300 nm 700 nm 1400 nm biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 37 Satellite Secondary constriction Centromere Primary constriction centromere = primary constriction telomer Sister chromatids biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 38 Centromere biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 39 13

14 Telomere biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 40 biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 41 biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 42 14

15 Types of chromatin Euchromatin: Heterochromatin: Active genes; DNA is transcribed; Contains coding regions. Non-active regions of DNA, Contains non-coding regions; Contains informational regions, unused in a specific cell; Could be constitutive and facultative. biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 43 Heterochromatin Constitutive: Facultative: Contains non-coding, repetitive sequences of DNA; Represents centromeres, Contains coding, but non-active sequences; May be transformed into euchromatin; telomeres, satellites, Assures: spacers between Cell differentiation; genes. Sexual differentiation; Control of ontogenesis biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 44 The same fragment of chromosome in three cells (A, B, C). E euchromatin, Hc constitutive heterochromatin, Hf facultative heterochromatin biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 45 15

16 Nucleolus part of nucleus responsible for biogenesis of ribosomes: Transcription of ribosomal genes and synthesis of precursor of rrna (45S); Processing of 45S rrna and formation of 3 types of rrna: 5,8S + 18S + 28S; Assembling of RNP: rrna 18 S + 33 ribosomal proteins = 40S small ribosomal subunit; rrna 28 S + rrna 5,8 S + rrna 5 S + 49 ribosomal biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 46 proteins = 60S large ribosomal subunit Steps in expression of ribosomal genes DNA P +1 18S 5,8S 28S T Pro-rRNA Transcription Processing rrna 18S 5,8S 28S Assembling 40S + 60S 18S + 33 proteins = 40S 28S + 5,8S + 5S + 49 proteins = 60S biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 47 biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 48 16

17 biologiemoleculara.usmf.md e.usmf.md pass.: bmgu Structure of nucleolus: Nucleolar organizer sequences of DNA containing ribosomal genes; rrnas: primary transcripts 45S; rrna 5S, rrna 5,8S, rrna 18S, rrna 28S; Ribosomal proteins; Enzymes required for synthesis of rrna; RNP 40S and 60S. biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 51 17

18 Interphase Telophase Prophase Anaphase Prometaphase Metaphase biologiemoleculara.usmf.md e.usmf.md pass.: bmgu 52 18