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The map of the human genome - distances between them There...

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The map of the human genome Many thousands of genetic markers have now been mapped so that there is a minimum of about one marker per centiMorgan and in some regions of the genome there are as many as ten markers per centiMorgan. On the left are two maps covering the same small region of chromosome 9 (a region in which I have a particular interest). The map on the right is a genetic map made by considering the inheritance of many markers (with names such as D9S66) in about 60 large families. The map on the left is not a genetic map, it is a map based on a large number of overlapping pieces of cloned DNA (currently being sequenced) and so it is an accurate reconstruction of the actual DNA sequence of that region of chromosome 9. As is to be hoped, the genetic map gives the same order of markers and approximately the same relative
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Unformatted text preview: distances between them. There are some differences, The gene ABO is not resolved from marker locus D9S150 on the genetic map whereas, in physical reality there is a good sized gap. Differences like this occur because the rate of genetic recombination is not absolutely even throughout the genome, some areas are hot spots and others are areas of reduced recombination. This is reflected in the genetic distances between pairs of markers. The total genetic map length of the human genome is about 3,000 cM and by a lucky coincidence, the total genome length is about 3,000 million basepairs. So on average, 1 cM is equivalent to 1 Mb (Mb = million basepairs). In this region of chromosome 9 there is an elevated recombination rate compared to the genome average and so here 1 cM = ~ 300 kb....
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