Asked Oct 3, 2019

How can one construct a genetic map or determine the middle gene based on single and double crossovers?


Expert Answer

Step 1

A linkage map or a genetic map can be defined as a table for a particular species or experimental population. It gives the position of genetic markers or its known genes related to each other on the basis of a recombination frequency. It is not on the basis of a definite physical distance beside each chromosome.

Step 2

Construction of a genetic map:

 To create a genetic map, researchers follow the steps:

  1. Recognize the order and distance present between the genes.
  2. Recognize the parental classes (ABC and abc) with no crossover.
  3. There will be mapping of any two loci.
  4. Then there is a mapping of any other two loci. This is how try to sketch a rough map.
  5. Then there will be mapping between the remaining two loci.
  6. Select the right map with the aid of distance value which fits better.
  7. Then the map with the real order of genes is drawn.
  8. Then there is analysis of the single crossover classes.

(A single crossover refers to when the homologous chromosomes are arranged and the ch...


Image Transcriptionclose

B Map based on A-B recombination 5 m.u A C Map based on A-Crecombination 3 m.u 3 m.u 5 m.u 8 m.u Possible combined maps B A C -2 m.u 3 mu. 5 m.u


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