Question:
Why are there so many introns in eukaryotic genes vs. prokaryotic genes.
why would a seemingly more advanced organism have a greater ratio of non-coding DNA.
doesn't it take too much energy to excise the introns and then splice the RNA back
together, making it inefficient?
Replies:
Great question.
Perhaps several things to consider-
Bacteria need to be efficient based on their niche. They need to metabolize
and reproduce quickly when conditions allow for fast growth. but then why
don't yeast work this way....?
EuKaryotes because of their emphasis on genetic recombination favor a lot of
crossing-over during the production of sex cells. Perhaps the introns allow
for breaks to occur on the chromosomes so crossovers will not occur within a
gene or key gene element. This process creates a huge variety of sex cells
not to mention offspring, without damaging specific genes.
We also know that in normal development and cell specialization that genes
reorganized on a given chromosome. "Jumping genes" may require these larger
intron segments in order to be shifted around. The immune response to a
particular invader say a virus works this way. When a lymphocyte becomes
sensitized to an invader certain genes have been shuffled (re organized) so
the cell makes antibodies that can bind only one of several billion invaders.
Other theories suggest that the DNA protects itself from carcinogens in some
indirect way. Just some ideas!
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