Biology:Deletion mapping
Deletion mapping is a genetic technique used to determine the approximate location of a mutation within a gene or chromosome. It is based on recombination between a strain carrying an unknown point mutation and a series of strains carrying known deletions.
Principle
In deletion mapping, an organism carrying a point mutation is crossed with multiple strains, each of which carries a deletion spanning a different region of the same gene.[1][2]
If recombination produces wild-type offspring, the point mutation must lie outside the deleted region. A functional copy of the gene can then be reconstructed from the intact DNA contributed by the two parental strains.[1][2]
If no wild-type recombinants are produced, the point mutation is inferred to lie within the deleted region. Because one parent lacks that region entirely, recombination cannot restore a complete wild-type sequence.[1][2]
Example
Consider a wild-type copy of gene A and a mutant allele carrying a point mutation at an unknown position. Two additional strains carry different deletions within the same gene, designated del-1 and del-2.[2][3]
In the figure, the point mutation lies within the region deleted in del-1. Crossing the point mutant with the del-1 strain is therefore not expected to produce wild-type recombinants: the point-mutant chromosome carries a mutation at that position, while the corresponding sequence is absent from the deletion chromosome.[2][3]
By contrast, the point mutation lies outside the region deleted in del-2. Recombination between the point-mutant and del-2 chromosomes can therefore produce a chromosome containing neither the point mutation nor the deletion. The recovery of wild-type recombinants indicates that the point mutation lies outside the del-2 deletion.[1][2][3]
Not every recombination event between the point mutant and del-2 will restore the wild-type allele. Only crossovers occurring at suitable positions can reconstruct an intact wild-type sequence.[1][2][3]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 Benzer, Seymour (1955-06-15). "Fine structure of a genetic region in bacteriophage". Proceedings of the National Academy of Sciences 41 (6): 344–354. doi:10.1073/pnas.41.6.344. PMID 16589677. PMC 528093. https://www.pnas.org/doi/abs/10.1073/pnas.41.6.344.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Benzer, Seymour (1961). "On the topography of the genetic fine structure". Proceedings of the National Academy of Sciences 47 (3): 403–415. doi:10.1073/pnas.47.3.403. PMID 16590840. PMC 221592. https://www.pnas.org/doi/abs/10.1073/pnas.47.3.403.
- ↑ 3.0 3.1 3.2 3.3 Sanders, Mark F.; Bowman, John L. (2021-07-13). "Chapter 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages". Genetic Analysis: An Integrated Approach (3rd ed.). Pearson. ISBN 9780135564172. https://www.pearson.com/en-us/subject-catalog/p/genetic-analysis-an-integrated-approach/P200000006908/9780135564172.
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