Transmission of genetic information

1. Transmission of genetic information Genetics and genomics for3rd year Dentistry students 13.02.2015.

2. Genetic informations (DNA) is passed - within cells of an organism - from one generation to next generation

3. Multicellular cell cycle M-phase cytokinesis mitosis M G1 G2 Go G2 Restriction point - Growth factors - anchorange Checkpoints: Restriction point G2 M (spindle) S Interphase

4. Regulators of cell cycle cyclin dependent kinases (Cdk-s) cyclins phosphatases other kinase regulatory proteins: activating and inhibitory kinases, kinase inhibitors, Aurora and polo like kinases (Plk) ubiquitin ligases universal and conservative

5. Due to the activity of cell cycle and checkpoint machinary DNA and centrosome are duplicated (interphase – S-phase) and halved in M-phase (mitosis) with high fidelity Genetically identical cells

6. G1 S meta-anaphase Intact DNA is replicated in then is precisely halved semiconservative way (for this centrosome is (only once), needed)

7. Structure of centrioles and centrosome (MTOC) Distal appendages Subdistal appendages PCM = pericentriolar matrix TuRCs = tubulin ring

8. Different kinases regulate the duplication and separation of centrosome

9. M phase(events and regulation)

10. Dramatic changes in M-phase (initiated by MPF) DNA microtubules nuclear envelope marker Interphase metaphase anaphase telophase

11. Initiation of M-phase: activation of MPF (M-phase promoting complex=Cdk1-B cyclin) Activating kinase B cyclin MPFi MPFi Cdk1 Inhibitory kinase phosphatase MPFa

12. Main substrates of MPF • lamins of nuclear lamina nuclear envelope breaks down • condensin complex  chromosome condensation • MAP-s (microtubule associating proteins)  mitotic spindle formation • phosphatase (+ feedback)  activation • GM130 (Golgi matrix protein)  disruption of Golgi • myosin II • activation (indirectly) of APC (anaphase promoting complex) There are much more substrates of MPF

13. from DNA to chromosome Phosphorylation of condensin induces the condensation of DNA

14. Cohesin Condensin Cornelia de Lange syndrome (SMC = structural maintance of chromosomes = ATP-ases + other proteins)

15. Cohesin Condensin Cornelia de Lange syndrome (SMC = structural maintance of chromosomes = ATP-ases + other proteins)

16. Centromere and kinetochore are not the same structures Chromosomal passenger complex telomere

17. Kinetochore

18. Scleroderma Autoimmune disease – autoantibodies produced againts kinetochore proteins

19. Mitotic phases

20. Mitotic spindle in metaphase polar

21. Types of kinetochore–microtubule attachments Kinetochors are Bioriented Monooriented Monooriented bioriented Normal in mitosis not normal in mitosis

22. Mitotic phases If kinetochor MT-s are attached to all kinetochors ensuring precise segregation of duplicated DNA, checkpoint machinary allows the cell to step over M checkpoint and it enters anaphaseand M-phase is completed. In anaphase sister chromatids separate.

23. Anaphase (Kinetochore MT depolymerisation) (Polar MT polymeriation)

24. Anaphase is promoted by Anaphase Promoting Complex (APC) MPF indirectly activates APC (needed to complete mitosis and to start cytokinesis) APC is a ubiquitin ligase  induction of protein degradation in proteasome (Securinand B cyclin, protein binding the centrioles)

25. APC Different kinases regulate the duplication and separation of centrosome

26. Cohesin Condensin (SMC = structural maintance of chromosomes = ATP-ases + other proteins)

27. Separase (activated by APC) and Plk are needed for the separation of cohesin 2. 1. Kinetochores are bioriented Amphitelic attachment Nature Reviews Molecular Cell Biology

28. Activity of APC Activation of phosphatases (completion of mitosis an d cytokinesis) Separation of cohesin

29. Activity of APC APCubiqutination of B cyclin degradation of B cyclin MPFi   activation of phosphatase  dephosphorylation of lamins  reformation of nuclear envelope condensin  chromosome decondensation MAP-s  disappearance of mitotic spindle (MPF effects are reversed)  cytokinesis

30. M-(spindle) checkpoint Van szabad kinetochor APC Cdc20 APC Cdh1

31. M-(spindle) checkpoint No free kinetochors Free kinetochore APC, stops in metaphase Cdc20 APC

32. Types of kinetochore–microtubule attachments Kinetochors are Bioriented Monooriented Monooriented bioriented Normal in mitosis not normal in mitosis

33. Aurora B activates M-checkpoint machinary Activated M (spindle) checkpoint Inactive M (spindle) checkpoint, enters anaphase

34. Cytokinesis is usually symmetric Contractile ring (actin és myosin II)

35. Asymmetric cytokinesis Ontogenesis, gametogenesis (couse – asymmetric mitotic spindle)

36. There are several forms of atypical mitosis (M-phase) • Have been listed and shown in practice • They result genetically different cell populations in an organism  mosaicism which can be the cause of genetic diseases (see later)

37. Type Non-disjunction Bridge formation (anaphase lag) Multipolar division Endomitosis (Endoreduplication) No cytokinesis Description Due to atypical duplication and division of centrosome chromosomes are pulled to more than two poles A chromatid is pulled from two poles. Lacking of kinetochor microtubules of a chromatid. DNA is duplicated, but during M-phase the nuclear envelope remains intact. • No separation of chromatids - Separation of chromatids Mitosis is not followed by cytokinesis. Giant cell, giant nucleus Polythene chromosomes More chromosome (polyploid cell) Multinucleated (giant ) cells. Different chromosome number. Consequence Breakage of chromosome (structural chromosomal aberration) Change of chromosome number. Typical Genetically identical cells. Atypical Genetically not identical cells (In the organism: mosaicism)

38. Strebhardt et al.Nature Reviews Cancer6, 321–330 (April 2006) | doi:10.1038/nrc1841

39. Transmission of genetic information from generation to generation • asexual reproduction – offsprings are genetically identical • with the parent (clones) • sexual reproduction – offsprings differs from the parents • and from each other (geneticvariability)

40. Genetically identical cells in an organism Genetically different individuals Genetically different cells

41. Genetic variability • significance • is increased by – mutations – sexual reproduction meiosis (generation of gametes) - homologous recombination (crossing over) - independent assortment of homologous chromosomes fertilisation

42. Genetic variability is important in prokaryotes,too Provided by horizontal gene transfer

43. Significance of meiosis • genetic variability (genetically different cells) • chromosome number is halved (2n  n)

44. Meiosis DNA replication (S) • Meiosis I – prophase metaphase anaphase telophase  DNA replication • Meiosis II – prophase metaphase anaphase telophase

45. Meiosis I. Prophase

46. Leptotene Bouquet arrangement = by their telomeres chromosomes bind to nuclear envelope later gather at one site - possible role of cytoskeleton - significance: chromosomes are closer to each other MTOC telomeres

47. Paternal chromosome maternal chromosome 2 sister chromatids 2 sister chromatids Zygotene Synapsis (pairing) of homologous chromosomes by the help of synaptonemal complex Bivalent chromosomes - tetrads formation, pseudoreduction

48. Zygotene Pairs of chromosomes By Chung-Ju Rachel Wang, Department of Molecular and Cell Biology, University of California, Berkeley, USA. 2nd Prize.OlympusBioScapes Digital Imaging Contest

49. Homologous chromosomes similarity – same shape, size and genes differences – different origin, (maybe) different allele of a gene In a diploid human cell: 22 pairs autosomes 1 pair sex chromosomes XX or XY

50. Pachytene Homologous recombination = crossing over Crossing over is obligatory (between non sister chromatids) Number of crossing overs: 13/chromosome pair