Earlier attempt to explain the process of Hereditary

• Heredity is transmission of traits or characters from one generation to another generation or several generations.

• Hereditary is the tendency to acquire the characteristics of offspring and these characteristics resemble the parents.

• However, offspring do not resemble exactly with their parents and get some difference in characters because they are produced by sexual reproduction.

• The offspring that are produced by sexual reproduction, has differences but these differences are not present in offspring that are produced by the Asexual reproduction. 

• The differences that are present in offspring due to sexual reproduction are called variations.

• Hereditary and variation both run collectively and lead the evolution.

👌👌Remember - Sexual reproduction is the ultimate source of variations.

• The branch of biology that deals with the genetic variation and process of heredity is known as Genetics.

Early attempts to study heredity and variation.

• Earlier human being made attempt to demonstrate the process the heredity but he derived the fact of process the heredity on the basis of hearsay and superstition.

• In the 18th century, Aristotle demonstrated about heredity that Mother has some inert matter and father is responsible to activate the inert matter of mother.

• Some biologist believed that both maternal blood and paternal blood are combined in offspring and lead the  process the heredity.

• Leonardo da Vince and Regnier de Graaf suggested that both father and mother contribute equally in the process the heredity.

• In 1679, When Swammerdamp was studying  the development of insects. He suggested that The development of an organism takes place by simple enlargement of minute particles present in either sperm or ova .

• These minute particles were named by him Homunculus.

• Later on, Wolf suggested that homunculus-like structures are not present in either sperm or ova but gametes have some special differentiated structure that may give rise to formation of a complete body after Fertilization. This theory of Wolf is known as the theory of Epigenesis.

• In 1868, Darwin postulated the Theory of Pangenesis. According to this theory, every organ of the body produces minute and invisible  hereditary particles, called gemmules or Pangenes.

• These Pangenes are transported through the bloodstream and assembled in gonads and finally move to the gametes.

• During Fertilization, these gemmules or pangenes fuse together and redistribute into different organs for the development.

• In 1892 Joseph Gottlieb Kölreuter, A German botanist, obtained a hybrid by pollinating a Tobacco plant. These hybrids are different.  On the basis of these hybrids, he   suggested that heredity is a natural process.

• Later on Knight and Gross conducted an experiment on Garden pea and observed uniform characters among the offspring in first generation and observed that generation of characters took place in second generation.

• But he could not explain the complete process of heredity and failed to formulate law of inheritance. They also did not analyze their result mathematically.