Basic principles of Heredity
The basic principle of heredity comes from the first theory that was proposed in 1866 by Gregor Mendel. Mendel’s research was based on the pea plant but the principles are applied to both plants and animals. It helps us to understand how we inherit different traits like eye and even the tongue rolling ability.
Inheritance in pea plant
There are 7 traits in the pea plant and Mendel selected all those that had two forms.
- Pea color (yellow or green)
- Pea shape (round or wrinkled)
- Plant height (tall or short)
- Pod color (yellow or green)
- Pod shape (inflated or constricted)
- Flower position (terminal or axial)
- Flower color (purple or white)
Mendel start his search with the pure-breeding plants because their progeny had the same traits as the parent plants. He cross-bred the plants and recorded the new results that he found.
The key principles of heredity developed by Mendel are as follows.
Fundamental theory of heredity
It is the concept of the passing of discrete units of heredity like genes from parents to children. Mendel found through his research that from the paired traits one was dominant and the other was recessive. That is why when the plants were cross-bred in the first progeny all plats were tall. The dominant gene showed its trait. These were called the carrier plants and when they were cross-bred, there were 75% chances that progeny would have dominant trait and 25% chances that it would should the recessive trait.
Principle of segregation
The inherited factors that determine the traits are separated during the reproductions into the reproductive cells by the process of meiosis. During fertilization, they randomly reunite.
It was proposed by Mendel that during reproduction it is very important that the genes separate randomly into the reproductive cells. This is the reason that the traits of the progeny cannot be determined until they have grown. The separation of genes during the process of meiosis occurs in the reproductive cells like pollen and ova in plants and sperms and eggs in animals.
Principle of independent assortment
The chromosomes have different genes at different locations and each chromosome will inherit them separately.
It was noticed that when peas of more than one trait were crossed the results were always different and most of the time they never matched the parents. The reason is that different traits are independently inherited by different chromosome. The ratio of occurrence of dominant trait even changed. There were more chances of progeny that will have both dominant and recessive traits.
After the publication of the Mendel’s laws it became easy to understand genetics and find out that how the traits are transferred from parents to their offspring. It is all due to the work Mendel that now we have been able to find the cure of many genetically transmitted disease. Now we can easily know what types of genes will cause the disease and so such crosses are prevented.