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Bioinformatics Module

Bioinformatics Module. Supplementary Lecture 1 Cell biology. Introduction to lecture 1. Introduction to cellular and multicellular biology: Our current understanding of “Life (living organisms)” the origins of life Overview of a cell: e.g. nucleus/chromosomes

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Bioinformatics Module

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  1. Bioinformatics Module Supplementary Lecture 1 Cell biology

  2. Introduction to lecture 1 • Introduction to cellular and multicellular biology: • Our current understanding of “Life (living organisms)” • the origins of life • Overview of a cell: e.g. nucleus/chromosomes • Two major cell classifications • Major cellular stages: cell division: normal cells and reproductive cells , change in type and death • Development process in mulit-cellualar organisms

  3. Life • Origins of life: • Formation of first organic molecules; e.g. DNA (deoxyribonucleic acid). • Formation of first unicellular organisms; bacteria, amoeba • Formation of multi-cellular organisms. • Evolution of organisms to ensure both adaptable and stable to the environment: (Look up the different environments in which life is know to exist)

  4. The Prokarytotic Cell • Viruses: • contain only DNA surrounded by a protein coat • require a cell (host) to reproduce • Prokaryotes (bacteria ): • contain no defined “nucleus” : the nuclear material floating is within the cytoplasm, • The DNA (nuclear material) is circular and referred to as a plasmid. • These cells are smaller and less complex that the eukaryotic cell (refer to animal cell). • Much more numerous and existed before eukaryotic cells.

  5. Cell classifications • Archaea • A unicellular organism similar in appearance (morphology) to bacteria. • A mix between prokarytoic and eukaryotic cells • Have no nucleus but similar “transcription/translation” to eukaryotic cells • Can survive in unusual harsh conditions: e.g. hot springs, salt lakes. • Eukaryotic cells: • Can be unicellular (ameobia) or multicellular (homo sapiens: “wise man”) • Have a nucleus containing nuclear material: DNA • Unlike prokaryotic and archaea, whose DNA is circular, the DNA is linear. • Exist in the form of a compacted DNA strands called chromosomes. • Includes fungi , plants and animals…

  6. The Eukaryotic cell

  7. Components (basic fnts) • Nucleus: • Nucleus contains nuclear material (“genes”) stores as long strands of DNA molecules in the form of chromosomes. • The nuclear material (nucleus) is surrounded by a semi-permeable membrane (shield) • In the homo sapiens ( human) nucleus there are 23 pairs of chromosomes including sex determinant chromosomes: the X and the Y chromosome. One of the pairs is from the father and the other from the mother.

  8. The Chromosomes of a Human genome: The image shows the 23 pairs (including X / Y). This is the chromosome set of a male. A female would have 2 Xs and no Y ; ref [1] chapter 1

  9. Other important Cell components • Ribosome: They protein producing factories of cells. They can exits either free in the cytoplasm or attached to the nuclear membrane. • Cell Membrane: semi-permeable and protects cell from “harsh” external environment but does allow certain “chemicals” like glucose, and proteins to pass into cell. • Mitochondria: the energy producing organelle for the cell. They also contain there own set of DNA and are inherited from the female. So can be used to track the female linage of a species; e.g. all females descend from “mitochondrial” eve.

  10. Cell states • In Multi-cellular organisms a cell can exist in a number of “states”; where each state has a different purpose. • Meiosis converts cell into a reproductive cell: produces to daughter cells which contains half the amount of DNA • Mitosis which duplicates the cell with the same amount of DNA • Differentiation: converts a cell into a different cell type (e.g. of cell types are: neuron, liver cell, skin cell….) • Quiescence: a quite “rest” state • Cell death (suicide) or programmed cell death • A combination of the states transform the conceived cell (a single cell (sperm combined with egg) into a fully formed organism.

  11. The Cells states: Mitosis and Meiosis Cross-over Mitosis normal (somatic) cell division produces 2 identical daughter cells. Meiosis cell division to produce sexual reproductive cells: it produce 4 cells which contain have half the amount of DNA chromosomes. Moreover parts of the chromosome pairs “cross over” increasing genetic variability.

  12. Different Cell states • Cellular differentiation: • similar to cell division but rather than producing two identical diploid somatic cells it produces 2 different types of diploid somaticcells : • It is the basis of multi-cellular organism development. [without such a process we would just be a clump of the “same” cell type • Is the reason that stem cells can be used to “produce” different types of organs • Quiescent state: • where the cell is performing its expected activity : e.g. detoxification by liver cells; transmission of neural signals by neurons (often referred to as the Go state in mitosis) [fig2.5 p23[1]) • Cell death [programmed] (apoptosis): • after several mitotic cycles or through significant damage a gene product causes apoptosis and a mutant form is associated with cancer (p. 26 [1])

  13. Steps in Organism development • Sexual fertilization: is the fusion of the 2 gametes to form the zygote: • Cellular differentiation: Essential the progenitor or Stem cell via various signalling molecules divide into different cell types and from there into different tissue types. • The first step seems to be that the cytoplasm is not the same in the daughter cells of the zygote. • The genome of each daughter cell then has different expression profile and ultimately different cell types. • These further differentiate to produce all the cell types (~263 in humans) that exist in the organism; [note cells can also go from normal to abnormal (malignant) ]

  14. Cell types • A human has about 300 distinct cell types. • A cell types essentially is its genetic profile: the set of genes that are “on” and that are “off” • A different profile means a different cell type. • A precursor cell type (stem cell) can changes its genetic profile [normally by interaction with external elements]. While a mature cell type only changes its profile when it becomes malignant or carcinogenic. • The “earlier” the precursor (e.g. stem cell) the more cell types it can form.

  15. References • [1]: klug, W.S. et al “essential of genetics” 7th or 7th ed. Pearson education

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