Nucleus and Mitosis. VIBS 443 and VIBS 602. Undergraduate Graduate Histology Lecture Series

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1 Nucleus and Mitosis VIBS 443 and VIBS 602 Undergraduate Graduate Histology Lecture Series Larry Johnson, Professor Veterinary Integrative Biosciences Texas A&M University College Station, TX 77843

2 Objectives Characterize the interphase nucleus including the cell cycle, nucleolus, chromatin, nuclear envelope, and nucleocytoplasmic interactions. Characterize mitosis including structures with definitions, mechanisms of chromosome movements, and cytokinesis.

3 Remember the proposed evolutionary involvement of the cell membrane in organelle formation. Eukaryotic cell Eukaryotic cell

4 Nucleus (interphase nucleus) Microtubules Intermediate filaments Stabilize nuclear envelope

5 Nucleus - archive of the cell Archive of the cell - nucleus encodes for all proteins and secretory products. All somatic cells have the same codes regardless of their final function in the body (e.g., nerve, epithelium, CT, muscle).

6 Heterochromatin - condensed chromatin Euchromatin dispersed for active transcription Nucleus Cells in an individual are the same in their genome, but they differ in its expression.

7 Nucleus Source of major informational macromolecules that direct protein synthesis. trna, mrna, and, rrna

8 Chromatin Nucleus Nucleoprotein - stain basic dye Nuclei

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11 Cell cycle Generation time varies with cell type 4-6 days in intestine absorptive cells Year in nerve cells

12 Cell cycle G1/S/G2/M GAP 2 M Mitosis GAP 1 S DNA synthesis GAP 1 GAP 2

13 Cell cycle Morphology varies with the cell cycle. Shown by differential interference contrast microscopy.

14 Dead stained cells Bright field Live unstained cells Phase contrast Nomarski differential interference contrast Dark field

15 Phase contrast light microscopy Cell cycle The cell cycle - cells round up for mitosis

16 rvox_qo 3IQknCEdc&featur e=related related

17 Nucleolus Cell fractionation to study nucleoli morphology - ribosome production Fibrous 50 A 45S 18S + protein 40S (small subunit) Granular 120 to 150 A 45S 28S + protein 60S (large subunit)

18 Nucleolus Metabolic activity of cell reflected in size of nucleolus Pituitary cell If axon is cut, size of nucleolus increases by 50% Oocyte Sertoli cell Leydig cell Nerve cell

19 Nucleolus To study the pathway of ribosome formation: Pulse chase experiment 3 H uridine for RNA Temporal appearance of radioactivity revealed that 3 H uridine first was seen over the nucleus, then nucleolus, and finally over the cytoplasm.

20 Nucleolus Ribonucleoproteins - Have an affinity for basic dyes and are the most conspicuous of stained nuclear organelles.

21 Nucleolus Disperses in cell division

22 Nucleolus Contains genes for ribosomal RNA.

23 Nucleolus Is essential for protein synthesis destined for cytoplasm. Note contribution of: Cytoplasm Nucleus Nucleolus to ribosomal production

24 Nucleolus Summary Pulse chase experiment 3 H uridine for RNA, Temporal appearance of radioactivity revealed that 3 H uridine first was seen over the 1) Nucleus, 2) Nucleolus, and finally over the 3) Cytoplasm 3 H uridine for RNA

25 Chromatin DNA double helix w/ protein 20 A thick Mitosis A thick

26 Chromatin 100s of miles of DNA in single cell packaged for mitosis. Beads on a string

27 Chromatin Heterochromatin sperm cell nucleus, inactive and dark Euchromatin nerve cell nucleus, active and light

28 Chromatin Histones and other proteins from cytoplasmic ribosomes

29 Polyribosomes

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32 Nuclear envelope Cell membrane is involved in organelle formation. Outer membrane - continuous with RER Inner membrane space - cisterna of RER

33 Nuclear envelope Nuclear pores nuclear cytoplasmic exchange Pore size 40 to 100 A Number = 2000/nucleus

34 Nuclear envelope Nuclear pores Gold study A Nucleoplasmins are molecular chaperones that transfer the DNA to the histone-dna complexes by binding to the histones.

35 Nuclear envelope Nuclear pores Ribosomal large subunit 120 to 150 A squeezes through 40 TO 100 A Pore size = 40 to 100 A

36 Nuclear envelope Nuclear pores

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38 Nuclear envelope Nuclear pores DNA not associated w/ pores RNA always associated w/ pores

39 Nuclear envelope Fibrous lamina or (nuclear lamina) Intermediate filaments

40 Annulate lamellae = nuclear pores like structures in RER

41 Why chromosomes, kinetochores, and centrioles? Chromosomes super coil prevents errors during mitosis Kinetochores most important part for division or segregation of chromosomes

42 Why chromosomes, kinetochores, and centrioles? Many plants have no centrioles If a centriole is removed, the cells still divide Real function unknown, except they are needed to be present to be pasted to the daughter cell for what ever their function is

43 Microscopy that allows observation of live cells.

44 Why do cells divide? Allow organism to increase in mass Replace damaged cells Reduce size of cell - improved diffusion

45 Why do cells divide? Avoid aging build up of waste products. If a portion of a cell is removed, it prevents cell division.

46 Mitosis Defined - cell division in which duplicated chromosomes divide into daughter cells that have identical chromatin content Mitotic figures in gut epithelium

47 Mitosis Cell division in gut epithelium

48 MITOSIS Definitions Karyokinesis - nuclear division Cytokinesis - division of cytoplasm Completion in 30 min to 2.5 hrs Cells in mitosis in intestinal epithelium

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50 Chromosomes - rod-like organelles, visible during cell division Number of chromosomes Diploid - 2n - full complement Haploid - 1n - half complement Polyploid - more than full complement (Down s syndrome)

51 Chromosomes rod-like organelles, that are visible during cell division Gene - hypothetical units of inheritance Linearly arranged along length of DNA Gene locus Deletion Translocation

52 Three main events in mitosis 1. Orientation (after chromosomal condensation and nuclear envelope breakdown) 2. Alignment 3. Segregation

53 MITOSIS

54 ORIENTATION ALIGNMENT SEGREGATION

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56 Events in mitosis Cytokinesis

57 Events in mitosis Cytokinesis

58 Events in mitosis Cytokinesis

59 Events in mitosis Cytokinesis

60 Events in mitosis Centrosome separation

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63 Mechanisms of chromosome movement Microtubule assembly - disassembly model Sliding microtubules model

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65 Chromosome movement Kinetochore, polar, and astral microtubules

66 Chromosome movement

67 Chromosome movement

68 Chromosome movement Three contributions 3 Kinetochore 1 Polar 2 Astral 1) polar, 2) astral, and 3) kinetochore microtubules

69 Chromosome movement

70 ybn_s&feature=related

71 Mitosis Developing ovarian follicle has many cells in mitosis.

72 Next time Peripheral blood

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76 Many illustrations in these VIBS Histology YouTube videos were modified from the following books and sources: Many thanks to original sources! Bruce Alberts, et al Molecular Biology of the Cell. Garland Publishing, Inc., New York, NY. Bruce Alberts, et al Molecular Biology of the Cell. Garland Publishing, Inc., New York, NY. William J. Banks, Applied Veterinary Histology. Williams and Wilkins, Los Angeles, CA. Hans Elias, et al Histology and Human Microanatomy. John Wiley and Sons, New York, NY. Don W. Fawcett Bloom and Fawcett. A textbook of histology. W. B. Saunders Company, Philadelphia, PA. Don W. Fawcett Bloom and Fawcett. A textbook of histology. Chapman and Hall, New York, NY. Arthur W. Ham and David H. Cormack Histology. J. S. Lippincott Company, Philadelphia, PA. Luis C. Junqueira, et al Basic Histology. Lange Medical Publications, Los Altos, CA. L. Carlos Junqueira, et al Basic Histology. Appleton and Lange, Norwalk, CT. L.L. Langley, et al Dynamic Anatomy and Physiology. McGraw-Hill Book Company, New York, NY. W.W. Tuttle and Byron A. Schottelius Textbook of Physiology. The C. V. Mosby Company, St. Louis, MO. Leon Weiss Histology Cell and Tissue Biology. Elsevier Biomedical, New York, NY. Leon Weiss and Roy O. Greep Histology. McGraw-Hill Book Company, New York, NY. Nature ( Vol. 414:88,2001. A.L. Mescher 2013 Junqueira s Basis Histology text and atlas, 13 th ed. McGraw Internet images and videos on biological presentations