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United States Department of Agriculture

Agricultural Research Service


Location: Cereal Crops Research

Title: Study of Chromosomes: Its Vital Importance in Agriculture, Biology, and Medicine

item Jauhar, Prem

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: October 30, 2008
Publication Date: November 15, 2008
Citation: Jauhar, P.P. 2008. Study of Chromosomes: Its Vital Importance in Agriculture, Biology, and Medicine. Meeting Abstract. Key Lecture at National Symposium on Chromosomes at Centre for Advanced Study in Cell and Chromosome Research

Technical Abstract: Chromosomes are rod-like structures in the nuclei of eukaryotic cells. DNA, the blueprint of life, combined with proteins (histones) is packaged into these dense string-like structures. Thus, chromosomes constitute an assembly of DNA and histones by which the genetic information is transmitted accurately from parents to the progeny. Although Gregor Mendel brilliantly formulated the laws of inheritance of traits in 1865, leading to the foundation of genetics, he did not have the benefit of the knowledge of chromosomes that were discovered later by Walter Flemming in 1882. Soon afterwards, the elucidation of parallelism between chromosome behavior during meiosis and genes (Mendel’s “factors”) during the course of breeding forced an alliance between cytology and genetics resulting in the birth of the hybrid science, cytogenetics, during the first decade of the twentieth century. The rapid growth registered by cytogenetics has no parallel in the history of science. Although plant breeding initially was developed essentially as an art, the application of the principles of genetics and cytogenetics made it a science-based technology which, in turn, greatly accelerated the process of crop improvement. Thus, the development of high-yielding varieties of crop plants launched the famous Green Revolution. Discoveries in chromosome research also unraveled several biological phenomena, and contributed to the understanding of evolution. For example, the evolution of polyploid crop plants could be explained by natural hybridization of wild progenitors in nature accompanied by the production of unreduced gametes with the sporophytic chromosome number. Understanding the basis of sex determination in animal species including humans was made possible by chromosome research. Lack of knowledge of the correct chromosome number in humans hampered the understanding of several physical and mental abnormalities. When in 1956 the correct human chromosome number was determined to be 46 by Tjio and Levan, it became possible to understand that the gain or loss of a chromosome or even a part of chromosome led to genetic disorders. Thus, it became known that Mongolian idiocy or a Down’s syndrome was caused by an extra dose of chromosome 21, i.e., trisomy 21 and “Cri du chat,” i.e., “cry of the cat” in babies was caused by the deletion of the short arm of chromosome 5. The chromosomal basis of persistent miscarriage among human females and several other disorders also became understood. The incidence of cancer was attributed to uncontrolled cell division leading to chromosomal abnormalities. Association between various types of cancers and certain chromosomal abnormalities was also elucidated. Various human female tumors of the breast, ovary and colon have typical chromosomal abnormalities. Different forms of leukemia are associated with specific chromosomal abnormalities as well. The chromosome abnormality that causes chronic myeloid leukemia (CML) is called Philadelphia chromosome (Ph). Clearly, chromosome research is pivotal to understanding several biological phenomena and has made tremendous contributions to all facets of human welfare. Specific studies will be described to explain the immense contribution of chromosomal research to agriculture, biology, and medicine.

Last Modified: 4/17/2014
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