Main principles of Heredity and Mendel’s experiments

Main principles of Heredity

When you notice some traits in your family tree ( grandfathers , parents , brothers and sisters ) you will find that there are two kinds of traits which are the hereditary traits and the acquired traits , The Hereditary traits are the traits that are transmitted from one generation to another .

The hereditary traits such as the hair colour , the skin colour , number of fingers and the blood groups , The acquired traits are the traits that are not transmitted from one generation to another such as the skill of playing football or writing .

How are the hereditary traits transmitted from one generation to another ?

They are transferred from one generation to another generation through the reproduction process and they are governed by basics and laws , The science which studies these laws is called Genetics .

Genetics is the science that researches the transmission of the hereditary traits from one generation to another by studying the differences and the similarities between the parents and the offspring .



In the asexual reproduction , the similarity is exact because the children are produced from one parent cell , In the sexual reproduction , there are similarities and differences between the children as it is resulted from coupling of two individuals .

Mendel’s experiments

The scientist Gregor Mendel was the first founder of heredity , Gregor Mendel was a monk , born in 1822 in Brunn , Austria , He performed his experiments using the pea plant in the garden of the monastery at Brunn .

Mendel carried out a group of experiments that explained how the hereditary traits are transmitted from one generation to another , And why some traits of the parents appear in their offspring .

Mendel performed his experiments using the pea plant because it is easy to be planted and it grows fast , Its life cycle is short , Its flowers are hermaphrodite , So,  the pea plant can be self -pollinated , The pea plant can be easily artifically pollinated ( the human intervention ) , The pea plant produces large number of plants in a generation , And it has several pairs of easily recognized contrasting traits .

Despite the numerous traits of pea plant , Mendel chose seven main traits to conduct his experiments such as the seed shape ( smooth or wrinkled ) , The seed colour ( yellow or green ) , The pod ( fruit ) colour ( green or yellow ) , The pod ( fruit ) shape ( swollen or sinuous ) , The flower colour ( red or white ) , The flower position ( side or end ) , the stem height ( tall or short ) .

The inheritance of one pair of contrasting traits 

Mendel studied the inheritance of each pair of these contrasting traits separated by the following specific scientific steps , Mendel’s experiment studied the inheritance of the seed colour trait of pea plant .

Mendel chose a pea plant that produces yellow seeds and other that produces green seeds for several generations , and he made self pollination for these plants for several generations to be sure of the purity of this trait .

Mendel planted the seeds of these plants , when the flowers appeared on the produced plants , he removed the stamens from these flowers before the anther become mature to insure that the plant does not self pollinate .

Mendel made cross-pollination for the flowers of yellow seed plants with the pollen grains from green seed plants , And for the flowers of green seed plants with the pollen grains from yellow seed plants .

Mendel covered the stigmas of the pistils in order not to cross pollinate from other flowers then he planted the produced seeds , He observed that all the produced plants ( first generation ) have yellow seeds and the green coloured seeds trait disappeared completely .

Mendel let the first generation plants do self-pollination then he planted the resulting seeds , so he observed that the quarter of the produced plants ( the second generation ) is green seeds and three quarters are of yellow seeds .

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