Now consider linkage - Now consider linkage If the A and B...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
Now consider linkage. If the A and B loci were on the same chromosome, to determine the proportions of the four gametes we would have to know the probability of recombination between the two loci. This probability is r , so "given" an A allele, (1-r) of the gametes would be AB, and r of the gametes would be Ab (i.e., recombinants). Similarly, given the a allele, (1-r) of the gametes would be ab, and r of the gametes would be aB (recombinants). Since there are two kinds of recombinant gametes resulting from crossover (e.g., reciprocals: Ab and aB), these two types are split evenly within the proportion r of recombinants (r/2 of each reciprocal). For example, if r = 0.02 (i.e., 2%), then the gametes produced by a "double heterozygote" such as the one three paragraphs above will result in the following proportions (1-r/2)AB : (r/2)Ab : (r/2)aB : (1-r/2)ab, e.g., 49%:1%:1%:49% respectively. For comparison, if there was no linkage between A and B, then the proportions of the four possible gametes would be 25%:25%:25%:25%. By definition then,
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/05/2011 for the course BIOLOGY MCB2010 taught by Professor Jessicadigirolamo during the Fall '10 term at Broward College.

Ask a homework question - tutors are online