Download Is the reason that stem cells can be used to “produce” different types

Bioinformatics Module
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
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
The wonder of Life
• Origins of life:
– Formation of first organic molecules; e.g DNA
– Formation of first unicellular organism; 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)
The Prokarytotic Cell
• Viruses:
– contain only DNA surrounded by a protein coat
– require a cell (host) to reproduce
• Prokaryotes (bacteria and Archea):
– contain no defined “nucleus” : the nuclear material
floating is within the cytoplasm,
– The DNA (nuclear material) does not form chromatin
and chromosomes [[no outer coat] and is circular.
– These cells are smaller and less complex that the
eukaryotic cell (refer to animal cell).
– Much more numerous and existed before eukaryotic
cells.
Cell classifications
• Eukaryotic cells:
– such as the animal cells have a nucleus (nuclear
material is protected) and linear.
– Includes fungi , plants and animals…
– In general are multi-cellular.
• differences between pro and euk
The Eukaryotic cell
Components (basic fnts)
• Nucleus:
– Nucleus (kernel) contains nuclear material (“genes”)
stores as long strands of DNA molecules surrounded
by “protective” proteins, histones, to form chromatin;
which in turn forms compacts chromadatids and
finally chromosome.
– 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.
– The nuclear material is surrounded by a semipermemable membrane (shield)
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
Cell components
• Ribosome: They protein producing factories
(organelle) of cells. They can exits either free
in the cytoplasm or attached, via the ER, to
the nuclear membrane.
• 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.
Cell organelles
• Cell Membranes: separates the interior of the cell from the external
environment.
• Both the nuclear and cell membrane are composed mainly of
lipids/proteins.
– The Lipids (or lipid bilayer) give it is fluidity and with the proteins give
in selective permeability
– The cell membrane allows various substances required for the viability
of the cell to pass through it: e.g. glucose, proteins and extra-cellular
signalling molecules.
– Nuclear membrane allows proteins and RNA (a type of DNA) to pass
through
• What is the function of the remaining organelles?
•
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.
Different Cell states
• mitosis and meiosis link
• Cellular differentiation:
– similar to cell division but rather than producing two identical diploid somatic
cells it produces 2 different types of diploid somatic cells :
– 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
• 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])
• 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])
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) ]
Organism development: Human
illustration
adapted from [2]
References
• [1]: klug, W.S. et al “essential of genetics” 7th
or 7th ed. Pearson education
• [2] Vaughan J. “Cellular Production ” School of
Biology, Dublin Institute of Technology
Sample exam questions
• Potential exam question:
– Explain the role played by cellular signalling in
organism development; illustrate you answer
where suitable.
– Describe the different states and how they
contribute to organism development; illustrating
your answer with suitable examples