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Notes on History of Genetics and Cytogenetics

1. History of Genetics and Cytogenetics

Source: Principles of Genetics and Plant Breeding by BD Singh 

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History of Genetics and Cytogenetics:

  • Genetics is the science of inheritance and variation.
  • Genes are the functional units governing individual characteristics.
  • Characters include morphological, anatomical, physiological, and behavioral features.
  • Examples of human characters are eye color, hair color, blood groups, etc.
  • Variation in characters indicates variation in the genes governing them.
  • Cytogenetics studies chromosomes and their effects on organism development.
  • Genes are universally accepted to be located in chromosomes.
  • Cytogenetics originated by combining cytology and genetics.
  • Cytology is the study of cell structures and functions.
  • Genetics and cytogenetics are distinct grossly but not at the molecular level.

Spontaneous Generation:

  • Organisms originate from pre-existing organisms of the same kind.
  • Living organisms do not arise from nonliving matter.
  • Spontaneous generation was believed by some biologists but refuted.
  • Redi and Spallanzani presented evidence against spontaneous generation.
  • Pasteur and Tyndall conclusively proved microbes do not originate spontaneously from organic matter.

Reproduction in Plants and Animals:

  • Babylonians and Assyrians knew about pollination in palm trees.
  • Eggs of birds were known, but mammalian eggs discovered later.
  • De Graaf identified mammalian ovarian vesicles as eggs.
  • Leeuwenhoek studied sperms but didn't speculate on fusion.
  • Spallanzani proved sperm's essential role in progeny development.
  • O. Hertwig provided conclusive proof of sperm-egg nucleus fusion.
  • Thomas Fairchild produced the first artificial plant hybrids in 1717.
  • Linnaeus, Koelreuter, and Gaertner produced artificial plant hybrids.
  • Amici described pollen tube entry into the ovary.
  • Strausberger described fertilization in angiosperms in 1884.


  • Heredity debate about the contribution of male and female parents.
  • Aristotle believed progeny form came from semen, substance from females.
  • Animalculists and ovists developed these concepts further.
  • Some claimed to see "homunculus" in human sperms.
  • Preformationists believed miniature human beings were in gametes.
  • Preformationists thought progeny developed from preexisting beings.
  • Improved microscopes challenged the idea of preformation.
  • Epigenesis replaced preformation as the accepted view.


  • Organs and tissues of adults develop from uniform embryonic tissues.
  • Differentiation from homogeneous embryonic tissues leads to organs.
  • Wolff proposed epigenesis but believed adult tissues originated de novo.
  • Von Baer suggested that adult tissues developed from embryonic tissues.
  • Von Baer's concept is the universally accepted view of organ development.
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