We may define genetics as the biological study that concerned with the subject of Heredity and Variation. The word genetics was coined by Dilliam Bateson in 1906. The principle of heredity states that there is a tendency of an offspring to posses characteristics similar to either or both its parents. This is because the parents reproduces itself in the offspring by causing the latter to organise in the same definite way it is because of heredity that individuals related by degeneration resemble one another.
Variation on the other hand, states that there is a tendency of the offspring to be different from their ancestors (parent) and one another. It is because of variation that differences exist between members of the same family and individuals of the same parents. These similarities and variation can be transmitted from one generation to another. It gives proper explanation and the opportunities for us to understand differences in characters. Skin colour, eye shape, hair length, and height are examples of such characters.
Characters are usually controlled by genes and development of certain make-ups. The sum total of genes that an individual inherits from the parent is known as its "Genotype" or genetics make-ups. It usually sets the limits within which characters can vary. Variations shown by inherited characters maybe due to:
* the effect of the environment, or
* the use or disuse of the body parts.
For example, a person may inherit genes for the development of a light-coloured skin, but the exact colour of any part of the skin is determined by the extent to which it is exposed to sunlight. This actual physical expression of characters is the person's "Phenotype". It is due to the interaction between a person's genotype and environment.
To explain better, the modifications of a person characters are brought about by:
* the environment, e.g tanned colour of the skin; or
* through use/disuse, e.g well-developed muscles/wasted muscles.
Information are stored in the genes, which is called the "Genetics Code". They contains all the necessary instructions for building up an individual. Most genes contains information to specifically take part in the development of a particular characters.
Characters are controlled by pairs (two copies) of genes. i.e the combination of both parent. The two copies of a gene for a given character separated during genetic formation. So, an individual gets one copy of a gene for a given character from each parent. Each parent have different strength and role. One might be dominant, while the other recessive. Example:
Parents=> Blue eyes (female) x Brown eyes (male) => Offspring (F1 generation) = ALL BLUE EYES.
Since only blue eyes colour is seen in F1 generation, we say that the blue eyes form of the character is dominant. However, most characters are known to appear in the next generation. During this process, we see that two characters are independently distributed or assorted. If members of the F1 generation are crossed among themselves, the F2 generation produced will show different ratio of blue and brown eyes.
There are probability in genetics. For example, if we toss a coin, the chance of getting heads or tails would be equal; i.e it is random occurrence. We can predict that the probability of getting heads, for instance, is 50%. However, this prediction will only be shown to be true if we make a large number of tosses.
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