What are Mendel’s Laws?

Mendel’s laws are fundamental laws of heredity (genetics). Inheritance is the passing on of traits and characteristics from parents to subsequent generations. The Augustinian priest, teacher and geneticist Johann Gregor Mendel (1822 – 1884) was the first researcher to methodically investigate the rules of heredity and is referred to as the “founder of the theory of heredity”. The existence of genes and  chromosomes was  unknown to him. He carried out his experiments on  peas  and  beans  . Three laws emerged from his crossing experiments, which were published in 1865 under the title: “Experiments on Plant Hybrids”.

uniformity law

If you cross two individuals of a species that differ in a trait for which they are homozygous, the offspring in the first daughter generation (F1 generation) will be the same (uniform) with regard to this trait. 

Example: The eye color brown (B) is dominant over the eye color blue (b). If one parent is homozygous for the eye color brown (BB) and the other parent is homozygous for the eye color blue (bb), you only have offspring with brown eyes in the F1 generation. However, they are mixed for the characteristic eye color brown (Bb).

division law

If the individuals of the F1 generation are crossed among themselves, then the individuals of the F2 generation are no longer the same, but split up according to certain numerical ratios. In the case of dominant-recessive inheritance, a dominant-to-recessive ratio of 3:1 is obtained. 

Example: Both parents are mixed for the eye color brown (Bb). In four children in the F2 generation, three have brown eyes and one has blue eyes. One child is homozygous for the characteristic of the eye color brown, two are homozygous. The child with the blue eyes is homozygous for the eye color trait.

Independence Act

If one crosses individuals of the same species that differ homozygous in several traits, the law of uniformity and division applies to each trait. In addition to the combination of traits of the parents, new combinations of traits appear in the F2 generation.

Small Encyclopedia of Genetics

  • dominant: (lat. rule); characteristic
  • DNA: deoxyribonucleic acid, storage form of genetic material
  • Gene: hereditary factor, hereditary disposition
  • heterozygous: heterozygous
  • homozygot: reinerbig
  • recessive: (Latin to go back); inferior to the dominant gene

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