9.c) Dominant character and Mendel's laws of heredity

The laws of heredity as evolutionary processes discovered by Gregor Mendel, Austrian Augustine monk, in his Investigations on hybrids in plants (1865).

Alongside to the theories of human origin and evolution in their strict sense is the Theory of Mendel on genetic inheritance, whose fundamental elements are gene combinations and their dominant or recessive character.

The theory of heredity of Mendel consists of the following two laws:

  • The Law of Scission

    Factors inherited from parents join in the resulting hybrid and separate when the hybrid reaches the adult stage and produces its sexual cells.

    Law of scission.

    This first law of heredity can be better explained using the example of white and red varieties in the Marvel of Peru plant:

    • The first generation produces all pink flowers. The second generation produces one white, two pinks and one red flower.

    • During the third generation, if white flowers mix with other white flowers, they produce white flowers; red flowers with other red flowers produce red flowers, and pink flowers repeat the results in the second generation of hybrids.

  • The Law of Dominant Character

    The dominant character does not destroy the recessive character in the hybrid; it merely conceals it.

    An example of the theory of Mendel on this law of heredity is the cross between white and grey rats:

    • The first generation produces grey rats. The second produces one white and three grey rats.

    • The appearance of white rats in a ratio of 1 to 4 in the second generation shows that the white (recessive gene) character has not been destroyed but remains hidden.

      Law of the dominant character.

    In the example of the law of heredity of the dominant character, only one character (mono-hybridization), has been included, but two or more (di-hybridization or poli-hybridization) can also happen, and the evolutionary process would be similar, although the possible combinations would grow in geometric proportion.

See chapter III about criticism of Mendel's theory