Everyone has heard of the seven wonders of the ancient world. Today I present my verdict on seven wonder discoveries in biological research, listed in rough chronological order.

Wonder 1: Cell TheoryCell theory, formulated in 1839, made three assertions: (a) All organisms are composed of basic units called cells; (b) The cell is the basic unit of structure and organisation in all living organisms; (c) New cells arise only from pre-existing cells.

Cell theory rationalised basic biology and contradicted the common notion that life can arise spontaneously from non-living matter.

Wonder 2: The Theory of Evolution Through Natural Selection.This is the most significant-ever insight into biology and was jointly proposed in 1858 by Charles Darwin (1809-1882) and Alfred Russell Wallace (1823-1913). It was already known that life on earth changes over long time periods. The theory of evolution explained the mechanism underpinning these changes natural selection. This theory draws all biology together into one unified framework. In its absence, biology would be reduced to a vast catalogue of unrelated observations.

Wonder 3: The Chemistry of LifeLife, unlike mechanical machines, works close to room temperature and without the assistance of significant temperature or pressure gradients. How then do cells grow, divide and create local order in a world that otherwise moves towards increasing disorder? This question was answered by biochemistry the chemistry of life.

A living cell is the end product of co-ordinated reactions between its innumerable chemical constituents metabolism. These reactions must proceed fast enough at room temperature to sustain life, and this is enabled by protein catalysts called enzymes, discovered in the 1800s. Cell metabolism is driven by energy, ultimately supplied by sunlight.

Wonder 4: Antibiotics and VaccinationsAntibiotics, discovered in 1928, are used to kill pathogenic microbes, and vaccination to provide immunity against disease has been in widespread use since 1900. Vaccination has eliminated many deadly diseases, including smallpox and polio.

Average life expectancy in 1900 was 50 years; today that figure is 82 years. Antibiotics and immunisation are one significant cause of this improvement. If we lost antibiotics and vaccinations today, life expectancy would gradually revert to 50-60 years.

Wonder 5: Discovering the Structure of DNAFaithful inheritance of parental characteristics by offspring is essential for biological evolution. The nature of the cells hereditary material was identified as nucleic acid (DNA) in 1944. In 1953, James Watson (born in 1928) and Francis Crick (1916-2004) made the greatest biological discovery of the 20th century when they solved the structure of DNA, a discovery that also indicated how DNA replicates and transmits genetic information from generation to generation.

DNA is a long molecule made of four sub-units A,T,G,C. Genetic information is encoded in the linear sequence (genes) of these subunits, dictating the structure/activity of all cell proteins, including all enzymes, thereby controlling the activities of the cell. Understanding DNA unlocked the secret of the molecular logic of life.

Wonder 6: CloningEvery animal body cell, including cells of the early embryo, contains a full set of the animals genes. Therefore, inducing any body cell into developing as embryonic cells develop should produce a genetic copy of the animal a clone. In 1996 Dolly the sheep was cloned in this manner.

Cloning offers many huge potential benefits, eg cloning animals, genetically modified to secrete a human hormone, to produce herds secreting large quantities of the hormone for use by patients deficient in the hormone. Cloning could also rebuild endangered animal populations or revive extinct animals.

Wonder 7: Induced Pluripotent Stem CellsThe human body is composed of over 200 tissues/organs skin, liver etc. Each tissue cell is differentiated to do a particular job. But all tissue cells develop from embryonic undifferentiated pluripotent stem cells.

In 2006 Shinya Yamanaka discovered how to transform differentiated body cells into pluripotent stem cells. These induced pluripotent stem cells (IPSC) can be coaxed to develop into specific adult tissues.

IPSCs have huge potential in many areas, eg regenerative medicine. New organs could be grown from patients own IPSCs to replace failing organs and without fear of immune rejection.

IPSCs are extremely useful for many research purposes, eg testing new drugs, and can substitute for stem cells extracted from human embryos, thereby avoiding ethical problems.

William Reville is an emeritus professor of biochemistry at UCC

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Story of life: Seven wonders of biological research - The Irish Times