Thomas morgan discovery of sex linked traits. Thomas Hunt Morgan.



Thomas morgan discovery of sex linked traits

Thomas morgan discovery of sex linked traits

The work for which the prize was awarded was completed over a year period at Columbia University, commencing in with his discovery of the white-eyed mutation in the fruit fly, Drosophila.

Morgan received his Ph. He then went to Europe and is said to have been much influenced by a stay at the Naples Marine Laboratory and contact there with A. He learned the importance of pursuing an experimental, as opposed to descriptive, approach to studying biology and in particular embryology, which was his main interest early in his career.

A useful account of Morgan's life and works has been given by G. Thomas Hunt Morgan with fly drawings. Commercial use or modification of this material is prohibited. In he moved with several of his group to Pasadena, where he joined the faculty of the California Institute of Technology or Caltech and became the first chairman of its Biology Division.

What factors were responsible for the successes that Morgan and his students achieved at Columbia University and how did these factors carry over to the Caltech era first under Morgan's, and later G. It is convenient to consider three time periods: Morgan and the Columbia Period to Morgan attracted extremely gifted students, in particular, A. Muller Nobel Laureate, They were to discover a host of new laws of genetics, while working in the "Fly Room," in the Zoology Department at Columbia.

Throughout their careers Morgan and these students worked at the bench. The investigator must be on top of the research if he or she is to recognize unexpected findings when they occur. Sturtevant has stated that Morgan would often comment about experiments that led to quite unexpected results: That organization recognized the basic research character of Morgan's work and supported research staff members in Morgan's group, such as C.

Bridges and Morgan's artist, Edith Wallace, who was also curator of stocks. The Carnegie grants required nothing more than an annual report from the investigators.

Federal support had not yet started and although universities were able to finance costs associated with teaching they were usually unable to support basic research.

During the Columbia period Morgan was clearly in his prime. His style of doing science must have been of paramount importance. He was not afraid to challenge existing dogma. He had become dissatisfied, even skeptical, of the formalistic treatment that genetics had taken in the period between the rediscovery of Mendelism in and He ridiculed explanations of breeding results that postulated more and more hereditary factors without any way of determining what those factors were.

He wanted to know what the physical basis of such factors might be. At that time it was generally assumed that chromosomes could not be the carriers of the genetic information. He wanted a suitable animal and chose Drosophila, because of its short life cycle, ease of culturing and high fecundity.

Also, large numbers of flies could be reared inexpensively -- an important factor during this period when there were very few funds available to support basic research.

Morgan was very thrifty when it came to purchasing laboratory equipment and supplies -- but, according to Sturtevant, generous in providing financial help to his students.

At the start of the work hand lenses were used. Only later did Bridges introduce stereoscopic microscopes. Bridges also devised a standard agar-based culture medium. Prior to that, flies were simply reared on bananas.

In addition, Bridges built the basic collection of mutant stocks, mapped virtually all of the genes and later, at Caltech, drew the definitive maps of the salivary gland chromosomes. His enormous research output may in part be attributed to his being a staff member of the Carnegie Foundation with consequent freedom from teaching and other academic obligations.

Morgan's first attempts to find tractable mutations to study were quite disappointing. Fortunately, he persevered and found the white-eyed fly 1. This led to his discovery of sex-linked inheritance and soon with the discovery of a second sex-linked mutant, rudimentary, he discovered crossing over.

Sturtevant in the Drosophila stock room of the Kerckhoff Laboratories. In a conversation with Morgan in about the spatial relations of genes in the nucleus, Sturtevant, who was still an undergraduate, realized that the sex-linked factors might be arranged in a linear order. He writes that he went home and spent the night constructing a genetic map based on five sex-linked mutations that by then had been discovered.

In Bridges and Sturtevant identified and mapped two groups of autosomal not sex-linked factors and a third such group was identified by Muller in The four linkage groups correlated nicely with the four pairs of chromosomes that Drosophila was known to possess. Proof that this correlation was not accidental came when Bridges used the results of irregular segregation of the sex chromosomes or non-disjunction to provide an elegant proof that the chromosomes are indeed the bearers of the hereditary factors or genes as they are now known.

Bridges published this proof in in the first paper of volume I of the journal Genetics. Sturtevant often commented on Morgan's remarkable intuitive powers. Thus, Sturtevant describes how after explaining some puzzling results to Morgan, Morgan replied that it sounded like an inversion 2. Sturtevant went on to provide critical evidence, purely from breeding results, that inversions do occur; it was only later that inversions were observed cytologically.

It seems clear that Morgan was not only a stimulating person but one who recognized good students, gave them freedom and space to work, and inspired them to make the leaps of imagination that are so important in advancing science.

Morgan and the Caltech Period to Robert A. Millikan with cosmic ray equipment. Morgan was invited by the astronomer, G. Hale had conceived the idea of creating Caltech some years earlier and had already recruited R. Millikan Nobel Laureate in Physics, and A. Noyes to head the Physics and Chemistry Divisions, respectively.

According to Sturtevant, Morgan told his group at Columbia of Hale's invitation and of how it was not possible to say no to Hale. Morgan accepted and came to Caltech in He brought with him Sturtevant, who came as a full professor, Bridges, and T. Dobzhansky, who later became a full professor. In addition to Sturtevant and Dobzhansky, the genetics faculty consisted of E. Schultz, who like Bridges was a staff member of the Carnegie Institution of Washington, participated in the teaching of an advanced laboratory course in genetics.

During this second period, many geneticists visited the Biology Division for varying periods of time. Those from foreign countries included D. Monod Nobel Laureate. Visiting professors included Muller and L. Morgan was well known outside of the scientific community and attracted interesting people. Professor Norman Horowitz, who was a graduate student in the Biology Division during this period, tells me that he remembers Morgan giving a tour of the Biology Division to the well-known author, H.

Such assistance was essential at that time, since Caltech is a private institution and received no support from the state or the federal government. In the latter half of this period, Morgan returned to his interest in marine organisms and did not follow the newer developments in genetics. Instead it was largely Sturtevant who carried on the Morgan legacy as far as genetics was concerned. Sturtevant also allowed his graduate students considerable freedom to choose their thesis projects and to consult with him on those projects or indeed on any matter.

I was fortunate to have been one such student, commencing in Sturtevant's door was always open to students and faculty. I well remember Morgan coming to Sturtevant's office to discuss matters affecting the Division. Sturtevant told us that the award of the Nobel Prize to Morgan in was an important factor in elevating the prestige and status of the Biology Division at the Institute.

At the time, the only other Nobel Laureate at Caltech was Millikan. From to , the Division was managed by a committee chaired by Sturtevant. Beadle and the Caltech Period to Beadle and Pauling with molecular model.

Beadle carried on the Morgan tradition of strongly supporting basic research and maintaining a stimulating intellectual atmosphere. He had collaborated with Sturtevant on a monumental study of inversions and together they wrote a textbook of genetics. He had collaborated also during that time with Sterling Emerson, and with E.

Beadle was clearly a part of the Morgan legacy. Beadle in lab coat. George Beadle and B. Courtesy of the Caltech Archives. Beadle received the Nobel Prize in Physiology or Medicine in for work carried out at Stanford University on the biochemical genetics of the bread mold, Neurospora. In his biographical memoir on Beadle, Horowitz ref. Sturtevant had shown that the vermilion eye color mutation is non-autonomously expressed in flies that are mosaic for the vermilion mutation and its wild-type allele.

Beadle and Ephrussi designed at Caltech a set of experiments, involving transplantation of larval imaginal eye discs, to study the vermilion-plus hormone, as they called the diffusible substance. They carried out these experiments in Paris in Ephrussi's laboratory. They were able to show that another eye color gene, cinnabar, lacks a cinnabar-plus substance and that the wild-type vermilion and cinnabar genes control sequential steps in a biochemical pathway leading to the brown eye pigment.

Beadle correctly realized that the fungus Neurospora would provide better genetic material for exploring such pathways.

Tatum co-winner with Beadle of the Nobel Prize and colleagues at Stanford were then successful in dissecting the biochemical pathways that are involved in the synthesis of vitamins and many amino acids in that organism. The Neurospora findings opened a new era, now known as molecular genetics. During Beadle's tenure as chairman, N. Edgar were added to the faculty in genetics. Horowitz and Mitchell had been associated with Beadle at Stanford and played major roles in developing the one-gene one-enzyme hypothesis that led to the award of the Nobel Prize to Beadle and Tatum.

Other appointments during Beadle's chairmanship that added strength in animal virology were R.

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Thomas morgan discovery of sex linked traits

The work for which the prize was awarded was completed over a year period at Columbia University, commencing in with his discovery of the white-eyed mutation in the fruit fly, Drosophila. Morgan received his Ph. He then went to Europe and is said to have been much influenced by a stay at the Naples Marine Laboratory and contact there with A.

He learned the importance of pursuing an experimental, as opposed to descriptive, approach to studying biology and in particular embryology, which was his main interest early in his career.

A useful account of Morgan's life and works has been given by G. Thomas Hunt Morgan with fly drawings. Commercial use or modification of this material is prohibited. In he moved with several of his group to Pasadena, where he joined the faculty of the California Institute of Technology or Caltech and became the first chairman of its Biology Division. What factors were responsible for the successes that Morgan and his students achieved at Columbia University and how did these factors carry over to the Caltech era first under Morgan's, and later G.

It is convenient to consider three time periods: Morgan and the Columbia Period to Morgan attracted extremely gifted students, in particular, A. Muller Nobel Laureate, They were to discover a host of new laws of genetics, while working in the "Fly Room," in the Zoology Department at Columbia.

Throughout their careers Morgan and these students worked at the bench. The investigator must be on top of the research if he or she is to recognize unexpected findings when they occur.

Sturtevant has stated that Morgan would often comment about experiments that led to quite unexpected results: That organization recognized the basic research character of Morgan's work and supported research staff members in Morgan's group, such as C. Bridges and Morgan's artist, Edith Wallace, who was also curator of stocks.

The Carnegie grants required nothing more than an annual report from the investigators. Federal support had not yet started and although universities were able to finance costs associated with teaching they were usually unable to support basic research. During the Columbia period Morgan was clearly in his prime.

His style of doing science must have been of paramount importance. He was not afraid to challenge existing dogma. He had become dissatisfied, even skeptical, of the formalistic treatment that genetics had taken in the period between the rediscovery of Mendelism in and He ridiculed explanations of breeding results that postulated more and more hereditary factors without any way of determining what those factors were.

He wanted to know what the physical basis of such factors might be. At that time it was generally assumed that chromosomes could not be the carriers of the genetic information.

He wanted a suitable animal and chose Drosophila, because of its short life cycle, ease of culturing and high fecundity. Also, large numbers of flies could be reared inexpensively -- an important factor during this period when there were very few funds available to support basic research. Morgan was very thrifty when it came to purchasing laboratory equipment and supplies -- but, according to Sturtevant, generous in providing financial help to his students.

At the start of the work hand lenses were used. Only later did Bridges introduce stereoscopic microscopes. Bridges also devised a standard agar-based culture medium. Prior to that, flies were simply reared on bananas. In addition, Bridges built the basic collection of mutant stocks, mapped virtually all of the genes and later, at Caltech, drew the definitive maps of the salivary gland chromosomes.

His enormous research output may in part be attributed to his being a staff member of the Carnegie Foundation with consequent freedom from teaching and other academic obligations. Morgan's first attempts to find tractable mutations to study were quite disappointing.

Fortunately, he persevered and found the white-eyed fly 1. This led to his discovery of sex-linked inheritance and soon with the discovery of a second sex-linked mutant, rudimentary, he discovered crossing over. Sturtevant in the Drosophila stock room of the Kerckhoff Laboratories.

In a conversation with Morgan in about the spatial relations of genes in the nucleus, Sturtevant, who was still an undergraduate, realized that the sex-linked factors might be arranged in a linear order. He writes that he went home and spent the night constructing a genetic map based on five sex-linked mutations that by then had been discovered. In Bridges and Sturtevant identified and mapped two groups of autosomal not sex-linked factors and a third such group was identified by Muller in The four linkage groups correlated nicely with the four pairs of chromosomes that Drosophila was known to possess.

Proof that this correlation was not accidental came when Bridges used the results of irregular segregation of the sex chromosomes or non-disjunction to provide an elegant proof that the chromosomes are indeed the bearers of the hereditary factors or genes as they are now known. Bridges published this proof in in the first paper of volume I of the journal Genetics. Sturtevant often commented on Morgan's remarkable intuitive powers.

Thus, Sturtevant describes how after explaining some puzzling results to Morgan, Morgan replied that it sounded like an inversion 2. Sturtevant went on to provide critical evidence, purely from breeding results, that inversions do occur; it was only later that inversions were observed cytologically. It seems clear that Morgan was not only a stimulating person but one who recognized good students, gave them freedom and space to work, and inspired them to make the leaps of imagination that are so important in advancing science.

Morgan and the Caltech Period to Robert A. Millikan with cosmic ray equipment. Morgan was invited by the astronomer, G. Hale had conceived the idea of creating Caltech some years earlier and had already recruited R. Millikan Nobel Laureate in Physics, and A.

Noyes to head the Physics and Chemistry Divisions, respectively. According to Sturtevant, Morgan told his group at Columbia of Hale's invitation and of how it was not possible to say no to Hale. Morgan accepted and came to Caltech in He brought with him Sturtevant, who came as a full professor, Bridges, and T. Dobzhansky, who later became a full professor. In addition to Sturtevant and Dobzhansky, the genetics faculty consisted of E.

Schultz, who like Bridges was a staff member of the Carnegie Institution of Washington, participated in the teaching of an advanced laboratory course in genetics. During this second period, many geneticists visited the Biology Division for varying periods of time. Those from foreign countries included D. Monod Nobel Laureate. Visiting professors included Muller and L.

Morgan was well known outside of the scientific community and attracted interesting people. Professor Norman Horowitz, who was a graduate student in the Biology Division during this period, tells me that he remembers Morgan giving a tour of the Biology Division to the well-known author, H.

Such assistance was essential at that time, since Caltech is a private institution and received no support from the state or the federal government. In the latter half of this period, Morgan returned to his interest in marine organisms and did not follow the newer developments in genetics. Instead it was largely Sturtevant who carried on the Morgan legacy as far as genetics was concerned. Sturtevant also allowed his graduate students considerable freedom to choose their thesis projects and to consult with him on those projects or indeed on any matter.

I was fortunate to have been one such student, commencing in Sturtevant's door was always open to students and faculty. I well remember Morgan coming to Sturtevant's office to discuss matters affecting the Division. Sturtevant told us that the award of the Nobel Prize to Morgan in was an important factor in elevating the prestige and status of the Biology Division at the Institute. At the time, the only other Nobel Laureate at Caltech was Millikan.

From to , the Division was managed by a committee chaired by Sturtevant. Beadle and the Caltech Period to Beadle and Pauling with molecular model. Beadle carried on the Morgan tradition of strongly supporting basic research and maintaining a stimulating intellectual atmosphere.

He had collaborated with Sturtevant on a monumental study of inversions and together they wrote a textbook of genetics. He had collaborated also during that time with Sterling Emerson, and with E. Beadle was clearly a part of the Morgan legacy. Beadle in lab coat. George Beadle and B. Courtesy of the Caltech Archives. Beadle received the Nobel Prize in Physiology or Medicine in for work carried out at Stanford University on the biochemical genetics of the bread mold, Neurospora.

In his biographical memoir on Beadle, Horowitz ref. Sturtevant had shown that the vermilion eye color mutation is non-autonomously expressed in flies that are mosaic for the vermilion mutation and its wild-type allele. Beadle and Ephrussi designed at Caltech a set of experiments, involving transplantation of larval imaginal eye discs, to study the vermilion-plus hormone, as they called the diffusible substance.

They carried out these experiments in Paris in Ephrussi's laboratory. They were able to show that another eye color gene, cinnabar, lacks a cinnabar-plus substance and that the wild-type vermilion and cinnabar genes control sequential steps in a biochemical pathway leading to the brown eye pigment.

Beadle correctly realized that the fungus Neurospora would provide better genetic material for exploring such pathways. Tatum co-winner with Beadle of the Nobel Prize and colleagues at Stanford were then successful in dissecting the biochemical pathways that are involved in the synthesis of vitamins and many amino acids in that organism.

The Neurospora findings opened a new era, now known as molecular genetics. During Beadle's tenure as chairman, N. Edgar were added to the faculty in genetics.

Horowitz and Mitchell had been associated with Beadle at Stanford and played major roles in developing the one-gene one-enzyme hypothesis that led to the award of the Nobel Prize to Beadle and Tatum.

Other appointments during Beadle's chairmanship that added strength in animal virology were R.

Thomas morgan discovery of sex linked traits

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5 Comments

  1. It is convenient to consider three time periods: Morgan's Nobel acceptance speech entitled "The Contribution of Genetics to Physiology and Medicine" downplayed the contribution genetics could make to medicine beyond genetic counselling.

  2. Morgan discovered a recessive mutation allele that caused white eyes. This led to his discovery of sex-linked inheritance and soon with the discovery of a second sex-linked mutant, rudimentary, he discovered crossing over. Legacy and honors Morgan left an important legacy in genetics.

  3. He also continued to study the evolutionary problems that had been the focus of his earliest work. Because all the sex-linked characters were usually inherited together, Morgan became convinced that the X-chromosome carried a number of discrete hereditary units, or factors.

  4. The Carnegie grants required nothing more than an annual report from the investigators. Morgan changed his work from traditional, largely descriptive morphology to an experimental embryology that sought physical and chemical explanations for organismal development. During the Columbia period Morgan was clearly in his prime.

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