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Marker densities and the mapping of ancestral junctions

Published online by Cambridge University Press:  14 April 2005

A. K. MACLEOD
Affiliation:
Roslin Institute (Edinburgh), Roslin, Midlothian, EH25 9PS, UK
C. S. HALEY
Affiliation:
Roslin Institute (Edinburgh), Roslin, Midlothian, EH25 9PS, UK
J. A. WOOLLIAMS
Affiliation:
Roslin Institute (Edinburgh), Roslin, Midlothian, EH25 9PS, UK
P. STAM
Affiliation:
Department of Plant Science, Wageningen University, P.O. Box 386, 6700 AJ Wageningen, The Netherlands
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Abstract

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In any partially inbred population, ‘junctions’ are the loci that form boundaries between segments of ancestral chromosomes. Here we show that the expected number of junctions per Morgan in such a population is linearly related to the inbreeding coefficient of the population, with a maximum in a completely inbred population corresponding to the prediction given by Stam (1980). We further show that high-density marker maps (fully informative markers with average densities of up to 200 per cM) will fail to detect a significant proportion of the junctions present in highly inbred populations. The number of junctions detected is lower than that which would be expected if junctions were distributed randomly along the chromosome, and we show that junctions are not, in fact randomly spaced. This non-random spacing of junctions significantly increases the number of markers that is required to detect 90% of the junctions present on any chromosome: a marker count of at least 12 times the number of junctions present will be needed to detect this proportion.

Type
Research Article
Copyright
© 2005 Cambridge University Press