Medical Genetics - V. M. Zaporozhan 2005

Introduction to Medical Genetics
Cytological Foundations of Heredity
Genetic Maps of Human Chromosomes

Genetic maps are diagrams that show the linear arrangement of genes and other genetic loci on a chromosome, along with the distances between them. Genetic distance is measured by the recombination frequency between homologous Chromosomes and is expressed in centimorgans (cM). One centimorgan corresponds to a 1% crossover frequency. Fig. 1.14 illustrates an example of the Genetic Map of chromosome 3, indicating the genes whose pathological Mutations lead to hereditary disorders. Such maps are referred to as the pathological Anatomy of the genome (see Appendix 2). Currently, over 9,000 human genes have been mapped (Table 1.4).

More comprehensive information can be found in the electronic catalog Online Mendelian Inheritance in Man (OMIM). The OMIM website is:

http://www3.ncbi.nlm.nih.gov/Omim/

Mapping genes associated with Hereditary diseases serves as a starting point for Gene identification. Knowledge of genetic maps is also essential for linkage-based disease Diagnosis, assessing the pathological effects of Chromosomal aberrations, and addressing issues in evolutionary and Population Genetics.

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Fig. 1.14. Pathological anatomy of chromosome 3

Table 1.4. Pathological anatomy of The Human Genome (number of mapped genes responsible for human diseases included in the OMIM genetic map as of September 1, 2005)