Polymorphism

Polymorphism

Lots of same/different stuff that can affect genotype - phenotype interactions.

Isotope - a form of an element with a different mass number from others. Examples carbon-12, carbon-13, carbon-14,... Isotopes are meant to have the same chemical properties as each other (carbon is carbon) but there are small differences in biochemistry (i.e. differential uptake of carbon-12 and carbon-14 in the dark phase of photosynthesis.)
Allotropy - the difference in elements like carbon that have more than one physical form (diamond, graphite, bucky balls & tubes etc.).

Biological polymorphism

Allelic variation. In sexually reproducing organisms, a gene locus can be occupied any one of a number of different alleles.
Possible example: eye colour in humans - generally one colour per person but different people have different colours.
Limits of this example:
- I'm not sure if a singe gene locus for eye colour has been identified.
- I think I remember something about eye colour changing with age.
- Left and right eyes are different colours in some animals. (How common rare is this)
Multiple loci for a single protein (function?). Fetal haemoglobin is different from adult haemoglobin. This is an example of differential gene expression and this variation can be spatial as well as well as temporal. For example there is "a Ca2+/2Na+ antiporter in mitochondria from most tissues, including heart, brain, brown adipose tissue, and ... a Ca2+/2H+ antiporter in liver." (Nicholls, D.G. & Ferguson, S.J. 1992, p.209)
Complexed enzymes require multiple precussor proteins to construct an active enzyme. If any of these precussor exists in multiple forms (due to the above two processes) then the complex can have multiple forms.
Isoforms
Isologs (Isologues)
Homologues

Pluralism in Biology
2-Oxoglutarate dehydrogenase. This complex is similar to Pyruvate dehydrogenase. Question: have these two TCA complexes evolved from a common ancestor? If so, how did this proposed ancestor catalyse two different reactions in a cyclic process?
How the immune system generates diversity of response. Six systems of organisation in which play a part in phenotypic and genotypic diversity.

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Created 20/6/99