The Genomes of Some Vertebrates Are Much Smaller Than Those

Essay

The genomes of some vertebrates are much smaller than those of others.For example, the genome of the pufferfish Fugu is much smaller than the human genome, and even much smaller than genomes of other fish, primarily because of the small size of its introns.
A.Describe a mechanism that might drive evolution toward small introns or loss of introns and could therefore account for the evolutionary loss of introns according to the "introns early" hypothesis.
B.Describe a mechanism that might drive evolution toward more or larger introns and could thereby account for the evolutionary appearance of introns according to the "introns late" hypothesis.