Geneticists and the Advancement of Genetics

In this article we will discuss about the contribution of geneticists towards the advancement of genetics.

1. Mendel Gregor (Johann):

He was an Austrian botanist who laid the foundation of the science of genetics. He worked with garden peas (Pisum sativum) and formulated two important laws of inheritance, viz., (i) law of segregation and, (ii) law of independent assortment. For this pioneer work he is rightly called as the father of genetics.

He presented his results in two papers at the meetings of Natural History Society on February 8 and March 8 in 1865 which were published in the proceedings of the society in 1866. However, his results were neglected for 34 years. Mendel died in 1884 and his work came into being after 16 yrs. of his death in 1900 when same results were independently discovered by de Vries, Correns and Tschermak.

2. Correns, Carl Erich:

He was a German botanist and geneticist who in 1900, independently but simultaneously with the biologists Tschermak (Austria) and Hugo de Vries rediscovered Mendel’s historic paper outlining the principles of heredity.

He conducted research with garden peas and came to the same conclusions which were drawn by Mendel in 1865. Later on, he worked with variegated plants such as four O’ clock (Mirabilis jalapa) and established the first conclusive example of extra chromosomal or cytoplasmic Inheritance.

3. Hugo, de Vries:

He was a Dutch biologist and geneticist. He rediscovered independently but simultaneously with Correns and Tschermak in 1900 Mendel’s Laws of inheritance. Later on, working with Oenothera lamarckiana he coined the term mutation for sudden heritable changes in the characters.

4. Tschermak, V.S.E.:

He was an Austrian botanist and geneticist. He was one of the co-discoverers of Mendel’s classic papers on the garden pea. Working with garden pea, Tschermak saw a cross reference to Mendel’s work and found that his results were in agreement with the findings of Mendel.

In the same year 1900, when Tschermak reported his findings, Hugo de Vries and Correns also reported their discoveries of Mendel’s papers. Later on, he applied Mendel’s Laws of heredity in barley, wheat-rye hybrids and oats hybrids for development of new plants.

5. Bateson, William and Punnett, R.C.:

He was a British biologist who coined the term Genetics in 1905. Bateson translated Mendel’s paper from German into English and became Mendel’s champion in England. He worked with pea and discovered the phenomena of linkage which is now known to be the result of closely located genes on the same chromosome. He also demonstrated that in pea certain characters are governed by two or more genes.

Punnett was an English geneticist who with Bateson discovered genetic linkage in 1905. Working with poultry and sweet peas, Punnett and Bateson discovered some fundamental concepts of genetics like linkage, sex determination, sex linkage and first case of autosomal linkage. In 1901, Bateson and Punnett founded the journal of genetics.

6. Johannsen, W.L.:

He was a Danish botanist and geneticist. He developed the concept of pure line. He worked with princess beans and coined the terms phenotype and genotype in 1903. He supported the mutation theory of Hugo de Vries, which refers to sudden heritable changes in a gene. The terms phenotype and genotype are widely used in genetics. He also recognized the importance of environment in the expression of characters.

7. Morgan, T.H.:

He was an American zoologist and geneticist famous for his experimental research with the fruitfly, Drosophila melanogaster. He established the chromosome theory of heredity in 1910. He showed that genes are linked in a series on chromosomes and are responsible for observable genetic traits.

For this work he received Nobel Prize for Physiology or Medicine in 1933. Thus, he was awarded Nobel Prize for his discovery of hereditary transmission mechanisms in Drosophila. He also observed sex linkage in Drosophila.

8. Bridges, C.B.:

He was a U.S. geneticist who helped establish the chromosomal basis of heredity and sex. He constructed detailed gene map of the giant chromosomes found in the salivary gland cells of fruitfly larva. He also discovered genie balance theory of sex determination and gene duplication in Drosophila. He had opportunity to work with Morgan.

9. Muller, H.J.:

He was a U.S. geneticist best known for his demonstration in 1927, that X-rays speed up the natural process of mutation. For experimental induction of mutation he was awarded Nobel Prize for physiology or medicine in 1946. He went to USSR and worked with N.I. Vavilov in Leningrad for about 4 years. He also helped to organize 7th International Congress of Genetics in Great Britain.

10. Beadle, G.W.:

He is a U.S. geneticist. He worked in the field of biochemical genetics and discovered that genes affect heredity by determining enzymatic structure. He worked on fruitfly with Morgan and on Neurospora with Edward Tatum. They exposed Neurospora with X-rays and studied the altered nutritional requirements of the mutants thus produced.

These experiments enabled them to conclude that each gene determined the structure of a specific enzyme which in turn allowed a single chemical reaction to proceed. This one gene one enzyme hypothesis concept won Beadle and Tatum (with Joshua Lederberg) the Nobel Prize for physiology or Medicine in 1958.

11. Tatum, E.L.:

He was a U.S. biochemist, whose research on bacteria, yeast and Neurospora created a new field of genetic studies known as molecular genetics. He worked in collaboration with Beadle and Ledefberg and developed the concept of one gene one enzyme hypothesis in 1941 for which they were awarded Nobel Prize for Medicine or Physiology in 1958.

They demonstrated that:

1. All biochemical processes in all organisms are ultimately governed by genes.

2. All these processes are resolvable into series of individual sequential chemical reactions or pathways.

3. Each reaction in some way is controlled by a single gene and,

4. Mutation of a single gene results only in an alteration in the ability of a cell to carry out a single chemical reaction. Later on, with Lederberg he discovered genetic recombination or sex in E. coli bacteria. This bacteria has become important source of genetic investigations for biochemical process after the discovery of one gene one enzyme hypothesis.

12. Sutton, W.S.:

Sutton was a U.S. geneticist who working with Grasshopper gave a hypothesis in 1903 that chromosomes carry the units of inheritance and they are the physical basis of the Mendelian laws of heredity. Thus, his work formed the basis for the chromosomal theory of heredity.

13. Avery, O.T.; Mac Leod, C.M. and Mc Carty, M.:

Avery was a Canada born U.S. bacteriologist. His research on pneumococcus bacteria laid the foundation of immunochemistry. He discovered that pneumonia causing bacteria produce a capsular envelope consisting of polysaccharide. He also discovered the phenomenon of transformation.

Avery with his coworkers (Mac Leod and Mc Carty) reported in 1944 that the substance which caused the transformation was deoxyribonucleic acid (DNA). Thus, they were the pioneer workers to demonstrate that DNA was the genetic material.

Mc Carty is a U.S. biologist, who with Avery and Mac Leod provided the first experimental evidence in 1944 that the genetic material of living cells is composed of DNA.

When the DNA extracted from capsulated bacteria (virulent) was mixed with living cells of second type of bacteria lacking capsules, the transformation occurred. The results of this experiment indicated that the substance responsible for the change was DNA.

14. Watson, J.D. and Crick, F.H.C.:

Watson is a U.S. geneticist and biophysicist. He is famous for his discovery of the molecular structure of deoxyribonucleic acid (DNA), the genetic material, in 1953. This investigation brought him (with Francis Crick and Maurice Wilkins) the Nobel Prize for Physiology or Medicine in 1962.

They proposed double helical model for DNA. This model also showed how the DNA molecule could duplicate itself. Thus, it became known how genes and eventually chromosomes duplicate themselves.

Watson published three books, viz:

(1) Molecular Biology of Gene in 1965,

(2) The Double Helix in 1968, and

(3) The DNA story in 1981.

Crick is a British biophysicist, who worked with Watson and Wilkins and discovered the DNA double helical model.

M.H. Wilkins is a New Zealand born British biophysicist whose X-ray diffraction studies of DNA proved crucial for the discovery of the molecular structure of DNA by James Watson and Sir Francis Crick. For this work the three Scientists were awarded Nobel Prize as mentioned above.

15. Barbara McClintock:

Miss. Barbara McClintock (1950), a U.S. geneticist working with maize observed that some genes are capable of changing their position on a chromosome and from one chromosome to another. Such genes are known as transposons or transposable elements or jumping genes.

Since this was an unusual finding, people did not appreciate it for a long time. This concept was recognized in early seventies and McClintock was awarded Nobel Prize for this work in 1983.

16. Benzer, S.:

He is a U.S. molecular biologist, who developed a method in 1955 for determining the detailed structure of viral genes and coined the term cistron to denote functional subunit of genes. He also explained non-sense mutations in terms of molecular sequence of DNA.

Benzer (1955) gave sub-divisions of genes viz., Cistron, Recon and Muton. These are the units of function, recombination and mutation with in a gene. He worked with r-II locus of T4 bacteriophage.

17. Jacob, F. and Monod, J.L.:

Jacob is a French biologist and Monod was French biochemist. They explained in 1961 the way in which genes regulate cell metabolism by directing the biosynthesis of enzymes. Jacob discovered that genes of bacteria are arranged in linear fashion in a ring and the ring can be broken at almost any point.

They developed the concept of gene regulation known as operon concept in 1962. They discovered regulatory genes which control the activities of structural genes. For this work, they were awarded Nobel Prize for physiology or medicine in 1965.

18. Nirenberg, M.W. and Khorana, H.G.:

Nirenberg is a U.S. biochemist, who played a major role in deciphering the genetic code. He demonstrated that with the exceptions of non-sense codons, each possible triplet (called a codon) of four different kinds of nitrogen containing bases found in DNA and in some other viruses in RNA ultimately causes the incorporation of specific amino-acid into a cell protein.

Har Gobind Khorana is an Indian born U.S. biochemist. He discovered how the genetic components of the cell nucleus control the synthesis of protein. He was awarded Nobel Prize for physiology or medicine with Nirenberg and Holley in 1968. Later on, he prepared the first artificial copy of a yeast gene in 1970.