Write a brief note about the gene concept given by Mendel

The concept of gene in heredity was first introduced through the experiments of Gregor Johann Mendel, who is called the Father of Genetics. He was an Austrian monk who worked between 1856 and 1863 on garden pea plants (Pisum sativum) in the garden of a monastery in Brno (now in the Czech Republic). Mendel wanted to understand how traits like flower color and seed shape pass from one generation to the next.

In 1866, Mendel published his results in the journal of the Natural History Society of Brunn. The original title of his paper was Versuche uber Pflanzen-Hybriden (Experiments on Plant Hybridization). In this paper, he explained that traits are passed through specific units which he called "factors". These factors are now known as genes.

The word "gene" was introduced later in 1909 by a Danish scientist Wilhelm Johannsen. The importance of Mendel's work was not understood during his lifetime. But later in 1900, three scientists Hugo de Vries, Carl Correns and Erich von Tschermak, rediscovered his experiments and confirmed his findings.

Mendel's ideas changed the way science understood heredity. He showed that inheritance follows clear rules and is not a random process. His work became the base of modern genetics, even before DNA and chromosomes were discovered.

Key Principles of Mendel's Gene Concept

Mendel's experiments showed that inheritance is not a blending of traits but is based on definite rules. His work laid the foundation for modern genetics. Later, his concepts were summarised as four main postulates, also known as laws of inheritance.

1. Principle of Paired Factors

Mendel stated that each trait is controlled by a pair of factors, one from each parent. These factors are now called genes. Each gene exists in two forms called alleles. If both alleles are same, it is homozygous. If different, it is heterozygous.

2. Principle of Dominance

When two different alleles of a trait are present, one allele masks the expression of the other. The visible allele is called dominant and the hidden one is recessive. For example, in a cross between tall (TT) and dwarf (tt) pea plants, all F1 plants are tall because tall is dominant over dwarf.

3. Law of Segregation (Mendel's First Law of Inheritance)

This law states that the two alleles of a gene pair separate or segregate during the formation of gametes. So, each gamete gets only one allele. This is why recessive traits can reappear in the next generation. This law explains the 3:1 ratio seen in monohybrid crosses.

4. Law of Independent Assortment (Mendel's Second Law of Inheritance)

This law applies when two or more traits are studied together. It states that alleles of different genes are inherited independently if they are located on different chromosomes. This results in new combinations of traits, as seen in the 9:3:3:1 ratio in dihybrid crosses.




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