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 semi-permemable 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

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.

Cross-over

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