Heredity in Humans

Heredity is passing of traits from parents to child. Sometimes child looks similar to parents, it is because child inherits traits like eyes, complexion, color of hairs.

Mendel’s contribution in heredity

Traits in child are influenced by the DNA of father as well as DNA of mother. Moreover, with each DNA there are two version of traits in child. But particularly, child shows only one trait. This trait can either be inherited from mother or from father. Mendel, through his experiment showed how traits are expressed in particular organism.

Mendel’s Experiment

Mendel in his experiment observed various contrast characteristics of garden pea plant like round or wrinkled seed, tall or short plants, white or violet flowers. He took two pea plants, one tall (TT) and other short (tt) in order to produce new plants. First generation or F1 Progeny, he observed that all plants produced were tall (Tt) and no mixture of traits were found. This observation raised a question that do all the plants in F1 progeny is exactly same as tall plant in parents. To find the answer he pollinated F1 plant by self pollination i.e Tt × Tt. Therefore, in second generation progeny or F2 Progeny, he observed that out of four plants one is short and rest of the three as tall i.e. (TT, Tt, Tt, tt).

Heredity

Heredity: Mendal’s Experiment

Conclusion of Mendel’s Experiment

Mendel with his experiment came on the conclusion that-

  • In F1 progeny, plants inherit both tallness and shortness trait but express only tallness trait.
  • Trait in whose single copy is enough to make plant tall is called dominant trait. Here, capital T denotes dominant trait.
  • In case of F2 progeny, one plant is short and other 3 are tall. Out of produced plant one is short because both the traits inherited are short.
  • Traits that show up it and only if both the traits are same then it is called recessive traits. Here small t denotes recessive trait.



Mechanism of heredity

DNA is information source that makes proteins in the cell. In DNA there are specific sections known as genes. For example, genes synthesise enzymes that control hormones. If genes are synthesised well, they produce lot growth hormones resulting into tallness of plant. However, if these genes are not synthesised properly, it may lead to dwarfism or shortness. Parents pass genes that control traits in their next generation. Each individual contain two set of genes one inherited from male parent and other inherited from female parent. These are located in chromosomes. Each germ cell takes one chromosome from each pair. When male and female germ cell fuses, to form new cell, the new organism will have stable number of chromosomes i.e. stable DNA.

Keywords: Mendel’s experiment, F1 progeny, F2 progeny, Dominant trait, Recessive traits, DNA, Genes, Chromosomes

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