3.6 Chromosomal Theory of Inheritance :
Gregor Johann Mendel published his work on inheritance of traits in 1866 but for some reasons, it remained unnoticed or unrecognized till 1900, as communication was not easy in those days. His work was not widely recognized. His approach of using mathematics and statistics to explain biological phenomenon was totally new and unacceptable to the then biologists.
As continuous variations were observed in nature, Mendel's concept of factors (genes) as stable and discrete unit which controlled the expression of characters, and that a pair of alleles did not "blend" with each other, was not accepted by his contemporaries. He also did not know the physical location of the 'factors' (genes) in the gametic cell.
In 1900, three scientists Hugo de Veries, Correns and von Tschermak, independently rediscovered Mendel's work on the inheritance of traits. Due to advancements in microcopy, scientists were able to observe cell division and the structure of chromosomes under microscope.
Walter Sutton along with Theodor Boveri (1903) studied the parallel behaviour of Mendel's factors (genes) and behaviour of chromosomes, at the time of meiosis.
Based on these observations, Chromosomal theory of Inheritance was put forth by Sutton and Boveri.
- This theory identifies chromosomes as the carriers of genetic material.
- This theory states that the chromosomes are present in pairs in somatic cells.
- During gamete formation homologous chromosomes pair, segregate and assort independently during meiosis. Thus, each gamete contains only one chromosome from a pair.
- Nucleus of gametes contains chromosomes, which carry all hereditary traits.
- Male and female gametes (sperms and eggs) carry all the hereditary traits.
- They are the link between parents and offsprings.
- The fusion of haploid male gamete and haploid female gamete, restores the diploid number of chromosomes of the species.
