Book contents
- Frontmatter
- Contents
- Preface
- 1 The history and evolution of the domestic fowl
- 2 The cellular organisation of genetic material
- 3 The transmission of inherited characters
- 4 Sex determination and sex-linked inheritance in the domestic fowl
- 5 Linkage and chromosome mapping
- 6 Genes controlling feathering and plumage colour
- 7 Muscle, nerve and skeleton
- 8 Lethal genes in domestic fowl
- 9 Quantitative genetics
- 10 Protein evolution and polymorphism
- 11 Immunogenetics of the domestic fowl
- 12 Gene cloning, sequencing and transfer in the domestic fowl
- APPENDIX I Linkage groups and the chromosome map in the domestic fowl
- APPENDIX II Oncogenes
- APPENDIX III The Chi squared (χ2) test
- APPENDIX IV One letter amino acid code
- APPENDIX V The genetic code
- Glossary
- Index
5 - Linkage and chromosome mapping
Published online by Cambridge University Press: 22 September 2009
- Frontmatter
- Contents
- Preface
- 1 The history and evolution of the domestic fowl
- 2 The cellular organisation of genetic material
- 3 The transmission of inherited characters
- 4 Sex determination and sex-linked inheritance in the domestic fowl
- 5 Linkage and chromosome mapping
- 6 Genes controlling feathering and plumage colour
- 7 Muscle, nerve and skeleton
- 8 Lethal genes in domestic fowl
- 9 Quantitative genetics
- 10 Protein evolution and polymorphism
- 11 Immunogenetics of the domestic fowl
- 12 Gene cloning, sequencing and transfer in the domestic fowl
- APPENDIX I Linkage groups and the chromosome map in the domestic fowl
- APPENDIX II Oncogenes
- APPENDIX III The Chi squared (χ2) test
- APPENDIX IV One letter amino acid code
- APPENDIX V The genetic code
- Glossary
- Index
Summary
The stages in genetic analysis
In the previous chapter sex-linked inheritance was discussed. In sex-linked inheritance the way in which certain characters are transmitted and expressed depends on the sex of the parents and offspring. The mechanisms involved depend on the genes for these characters being carried on one of the sex chromosomes, usually on the Z chromosome in the fowl since it is much larger than the W chromosome. In general, characters will show linked inheritance if the genes responsible are on the same chromosome, whether on the autosomes or sex chromosomes. The closer the genes are on the chromosome the stronger is the linkage. Linkage between two genes is a measure of the probability of them being transmitted together to offspring. An important goal of genetic analysis is to determine the positions of all the genes on the chromosomes and how their transmission and expression are controlled. This heightened understanding would enable genetic predictions to be made more accurately.
The process can be divided into a number of stages. (i) The first is to establish that a character is a genetically inherited character, and that it is inherited in Mendelian fashion. Some characters may be environmentally controlled. Others may be polygenetic, i.e. controlled by several genes (these are considered further in Chapter 9) and although each gene follows the normal Mendelian pattern, the overall analysis is rather complex.
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- Genetics and Evolution of the Domestic Fowl , pp. 63 - 78Publisher: Cambridge University PressPrint publication year: 1991