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Background

If linkage strength between any two gene loci is 70%, what would be the amount of crossing over between these loci?

(a) 15% (b)30% (c) 70% (d) none of these.

My approach at understanding the concept

I didn't find much about linkage strength from any authentic source.

I can think of two things :

  • The strength of a linkage would be greater if the spatial separation between two genes is less and the lesser if the separation is more. This is semantic. But,

  • how can it be represented in percentage? What does this 100 mean in this 70%? The separation between two genes can be more than 100 map units.

Question:

What does linkage strength mean? How is it related to amount of crossing over (number of recombinants)?

N.B. I would appreciate answers citing some authentic sources.

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  • $\begingroup$ nature.com/scitable/definition/linkage-51 $\endgroup$ – canadianer Apr 24 '17 at 19:52
  • $\begingroup$ With the above source answer is b) as the two gene loci are inherited together in 70% of the cases (which is the linkage strength). In cases were the distance is large the linkage strength depends on the ploidy level of the organism. Eg. 100% if haploid, 50% if diploid, 33% if triploid and 25% if tetraploid. In other words the linkage strength can only reduce to the lowest level possible, if the process is entirely random. $\endgroup$ – Jeppe Nielsen Apr 25 '17 at 0:10

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