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Most of our characteristics are encoded by a pair of alleles. These are different forms of the same gene, one inherited from the father and one from the mother. Inheriting a mutated allele can lead to diseas...

Enzymes are biological catalysts. They speed up reactions although they are not changed in the reaction. Enzymes are proteins, and therefore are folded chains of amino acids with a specific shape. This shape...

Photosynthesis is the process by which green plants and some bacteria absorb light energy from the sun using chlorophyll (a pigment in the leaves of plants responsible for the green colour) which leads to nu...

A reflex arc describes what controls a reflex reaction in humans. When something happens to an organism that needs a quick response a reflex action occurs. It allows the action to be 'unthinking'. A stimuli ...

You could refer to the following. Shoots grow upwards towards light (positive phototropism) and grow against the force of gravity (negative gravitropism). Roots grow with the direction of gravity (positive g...