Principle of linkage( pedigree)analysis Gives a hint about the position of a genetic disorder associated with a different phenotype The top diagram shows paternal (blue)and maternal(red) chromosomes aligned in a germ cell, a cell that gives rise to eggs or sperm. Three DNA sequences are shown, labelled A, B and C. The capital letters represent the patemal alleles and the lower case letters represent the maternal alleles. The middle panel shows the physical process of recombination, which involves crossing over of DNA strands between the paired chromosomes. The bottom panel shows what happens when the crossover is resolved. The maternal and paternal alleles are mixed(recombined)and these mixed chromosomes are passed to the sperms or eggs A is the disease gene and B and c are genetic markers, recombination is likely to occur much more frequently between A and c than it is between A and B. this allows the disease gene to be mapped relative to the markers b and cThe top diagram shows paternal (blue) and maternal (red) chromosomes aligned in a germ cell, a cell that gives rise to eggs or sperm. Three DNA sequences are shown, labelled A, B and C. The capital letters represent the paternal alleles and the lower case letters represent the maternal alleles. The middle panel shows the physical process of recombination, which involves crossing over of DNA strands between the paired chromosomes. The bottom panel shows what happens when the crossover is resolved. The maternal and paternal alleles are mixed (recombined) and these mixed chromosomes are passed to the sperms or eggs. If A is the disease gene and B and C are genetic markers, recombination is likely to occur much more frequently between A and C than it is between A and B. This allows the disease gene to be mapped relative to the markers B and C Principle of linkage ( pedigree) analysis. Gives a hint about the position of a genetic disorder associated with a different phenotype