By Dr Ananya Mandal, MD
Gregor Mendel the “Father of Genetics”
History of genetic research began with Gregor Mendel the "Father of Genetics". He had performed an experiment with plants in 1857 that led to increased interest in the study of genetics. Mendel who became a monk of the Roman Catholic Church in 1843, studied at the University of Vienna from where he studied mathematics, and then later performed many scientific experiments with plants to study inheritance of traits.
His experiment that led to the initial beliefs of genetics involved growing thousands of pea plants for 8 years. He was forced to give up his experiment when he became abbot of the monastery. He died in 1884 but his experiments still form the basis of genetics and gave a fair idea of inheritance.
Although Mendel did not use the term gene, his results explained the basic concepts of inheritance.
The rediscovery of Mendel’s work
Mendel’s work was first published in 1866 and it was rediscovered in 1900 by three European scientists, Hugo de Vries, Carl Correns, and Erich von Tschermak, who had reached similar conclusions from their own research. However, the units that transmitted or contained this genetic material was not yet known.
Mendel was the first to distinguish between dominant and recessive traits that can be inherited from parents to offspring. He also formed the basic ideas about a heterozygote and homozygote as well as the difference between genotype and phenotype. Genotype describes the genetic makeup of an individual while phenotype signifies the visible traits of that organism.
Friedrich Miescher and Richard Altmann
Friedrich Miescher (1844-1895) discovered a substance he called "nuclein" in 1869. Later he isolated a pure sample of the material now known as DNA from the sperm of salmon, and in 1889 his pupil, Richard Altmann, named it "nucleic acid". This substance was found to exist only in the chromosomes.
Hugo de Vries
By 1889 Hugo de Vries wrote an independent book called ''Intracellular Pangenesis'' citing similar findings. He was unaware of Mendel’s work then. He coined the term "pangen" for "the smallest particle one hereditary characteristic".
Chromosomes and genes
Darwin used the term Gemmule to describe a microscopic unit of inheritance. This came to be known as Chromosomes. Chromosomes, however, were first observed during cell division by Wilhelm Hofmeister as early as 1848.
Wilhelm Roux in 1883 speculated that chromosomes are the carriers of inheritance. Danish botanist Wilhelm Johannsen coined the word "gene" ("gen" in Danish and German) in 1909 to describe these fundamental physical and functional units of heredity. William Bateson in 1905 coined the term genetics from the word gene.
Thomas Hunt Morgan
In 1910, Thomas Hunt Morgan showed that genes reside on specific chromosomes. Depending on this knowledge Morgan and his students began the first chromosomal map of the fruit fly ''Drosophila''. Frederick Griffith, a scientist, was working on a project in 1928 that formed the basis that DNA was the molecule of inheritance and could be transferred.
In 1941 genetic mutations causing errors in specific steps in metabolic pathways was shown by George Wells Beadle and Edward Lawrie Tatum and the "one gene" hypothesis was formed.
James Watson and Francis Crick
In 1953 two scientists, James Watson and Francis Crick, were trying to put together a model of DNA and discovered the double helix structure.
It was in 1972 when Walter Fiers and his team at the Laboratory of Molecular Biology of the University of Ghent (Ghent, Belgium) determined the sequence of a gene in the Bacteriophage MS2 coat protein. Richard J. Roberts and Phillip Sharp found the genes can be split into segments making it possible that a single gene might be coding for several proteins.
Lates 90’s and post 2000
It was much later in the late 90’s and after 2000 that it was found that regions of the DNA producing distinct proteins may overlap and genes are one long continuum. The sequencing of the human genome and other genomes shows that rather few genes (~20 000 in human, mouse and fly, ~13 000 in roundworm, >46 000 in rice) encode all the proteins in an organism. These protein-coding sequences make up 1–2% of the human genome. A large part is non-coding DNA.
Naming conventions of genes
Naming convention of genes was established by the HUGO Gene Nomenclature Committee (HGNC) for each known human gene. All approved symbols are stored in the [http://www.genenames.org/cgi-bin/hgnc_search.pl] HGNC Database. Each symbol is unique and each gene is only given one approved gene symbol.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)