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#chromosome mapping

2 public questions tagged with this topic.

Linkage and Mapping

The maximum recombination frequency possible between two genes is

Recombination frequency quantifies proportion of recombinant gametes generated by crossing over between homologous chromosomes during meiosis. Maximum fifty percent occurs when loci unlinked yielding equal parental and recombinant classes in progeny because random chromatid segregation and occasional multiple exchanges equalise combinations. Frequency cannot exceed fifty percent even with many crossovers because each meiosis with single crossover involves only two chromatids and chromatid sampling remains random. This ceiling distinguishes unlinked loci from linked loci where recombinants remain minority below fifty percent threshold in test crosses.

Ref: Hartl & Ruvolo, Genetics, 6th ed., Chapter 5: Recombination Frequency Caps at Fifty Percent Maximum

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Gene Dissection and Complementation

Somatic cell hybridization is mainly used for

Somatic cell hybridization fuses human cells with rodent cells usually mouse creating heterokaryons containing both genomes that subsequently lose human chromosomes randomly during mitotic divisions while retaining mouse complement stably. Clones retaining different sets of human chromosomes screened for human-specific enzyme activity or DNA marker presence allow assignment of gene to particular chromosome via concordance analysis. Panel of hybrids with overlapping retention patterns refines regional localisation pioneering human gene mapping before recombinant DNA techniques enabling first physical assignments of many loci.

Ref: Griffiths et al., Introduction to Genetic Analysis, 12th ed., Chapter 12: Somatic Cell Hybrids for Physical Mapping

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