Book contents
- Frontmatter
- Contents
- List of figures
- Acknowledgments
- Introduction
- PART I FROM REPRODUCTION AND GENERATION TO HEREDITY
- PART II FAKTOREN IN SEARCH OF MEANING
- PART III THE CHROMOSOME THEORY OF INHERITANCE
- 5 Chromosomes and Mendelian Faktoren
- 6 Mapping the chromosomes
- 7 Cytogenetic analysis of the chromosomes
- PART IV GENES AS THE ATOMS OF HEREDITY
- PART V INCREASING RESOLVING POWER
- PART VI DEDUCING GENES FROM TRAITS, INDUCING TRAITS FROM GENES
- PART VII WHAT IS TRUE FOR E. COLI IS NOT TRUE FOR THE ELEPHANT
- Concluding comments
- Bibliography
- Index
6 - Mapping the chromosomes
Published online by Cambridge University Press: 07 August 2009
- Frontmatter
- Contents
- List of figures
- Acknowledgments
- Introduction
- PART I FROM REPRODUCTION AND GENERATION TO HEREDITY
- PART II FAKTOREN IN SEARCH OF MEANING
- PART III THE CHROMOSOME THEORY OF INHERITANCE
- 5 Chromosomes and Mendelian Faktoren
- 6 Mapping the chromosomes
- 7 Cytogenetic analysis of the chromosomes
- PART IV GENES AS THE ATOMS OF HEREDITY
- PART V INCREASING RESOLVING POWER
- PART VI DEDUCING GENES FROM TRAITS, INDUCING TRAITS FROM GENES
- PART VII WHAT IS TRUE FOR E. COLI IS NOT TRUE FOR THE ELEPHANT
- Concluding comments
- Bibliography
- Index
Summary
In their classical textbook of 1939 Sturtevant and Beadle noted that:
[l]inkage was first discovered, in the sweet pea, by Bateson and Punnett in 1906. The interpretation they gave is now discredited; but in the same year Lock suggested that, if homologous chromosomes undergo exchanges of materials (as has been suggested by Correns in 1902 on dubious theoretical grounds), then failure of such interchange might account for linkage – i.e., he postulated that linkage is due to genes lying in a single chromosome pair, and that crossing over is due to exchange of materials between homologs.
Sturtevant and Beadle (1962 [1939], 360)Morgan's concern for the need to distinguish between the production of apparently unrelated and often variable manifold phenotypes of a gene, and of genotypic coupling, the constantly frequent co-inheritance of distinct factors, which had been confounded in the concept of unit character, is exposed in Sturtevant's description of the “moment of insight” many years later, in his A History of Genetics:
In 1909 Castle published diagrams to show the interrelations of genes affecting the color of rabbits. It seems possible now that these diagrams were intended to represent developmental interactions, but they were taken (at Columbia) as an attempt to show the spatial relations in the nucleus. In the latter part of 1911, in conversation with Morgan about this attempt – which we agreed had nothing in its favor – I suddenly realized that the variations in strength of linkage, already attributed by Morgan to differences in the spatial separation of the genes, offered the possibility of determining sequences in the linear dimension of a chromosome.
Sturtevant (1965, 47)- Type
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- Genetic AnalysisA History of Genetic Thinking, pp. 94 - 107Publisher: Cambridge University PressPrint publication year: 2009