Which of the following would contribute most to successful exon shuffling?
(a) shorter introns
(b) a haploid genome
(c) exons that code for more than one protein domain
(d) introns that contain regions of similarity to one another
Choice (d) is the correct answer. Exon shuffling is facilitated by long introns [thus choice (a) is incorrect] and by short exons that each code for one protein domain [thus choice (c) is incorrect]. Because exon shuffling can occur by recombination between introns, introns with regions of similarity to one another will facilitate shuffling. A haploid genome will probably be less prone to exon shuffling than a diploid genome [thus choice (b) is incorrect], because having two copies of each gene allows an organism to keep one copy of the gene as a backup while it shuffles the other copy.
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