Good Evening and Welcome to the latest gameshow craze sweeping the nation! We've got science, we've got retro music, and we've got eighties-techno-fonts, it's-
This week on Selection Or Not?!, we explore one of most vital and yet little-understood facts of evolution: mutations! We all know they cause evolution, but do mutations evolve themselves? Does the rate of mutations vary and evolve? Well, let's ask our qualified expert!
...This just in, we do not have a qualified expert. So instead, you'll get the unqualified musings of your lovely host.
As all you lovely audience members know, evolution is based on change. You also know that natural selection is one of evolution's driving forces! But how do we know natural selection is happening? Well let's ask Darwin, the first man to ever conceive the idea, about his 5 requirements!
...This just in, Darwin apparently passed away several centuries ago. Instead, let's consult our lovely and yet increasingly confused host!
For our new audience members, here's how the contest works: We put a trait through Darwin's 5 postulates of Natural Selection, and if it meets them all, then it's selection! Now, make your predications about this week's topic: Mutation Rates!
But what are Darwin's 5 postulates? Well, I'm glad you asked! First, there must be a fight for survival between individuals. Second, only some individuals can survive this fight. Third, individuals must exhibit variation. Fourth, some of that variation must be heritable. And five, some forms of variation must be favored in the fight for survival between individuals.
This should all culminate with the individuals who have the favored variations being the ones who win the fight for survival!
You know the drill! If it passes all five postulates, then natural selection could be acting up it. Are you ready? Then let's play-
First up, Darwin's first and second postulates: the Fight for Survival and There Can Only Be One. Is there competition between individuals with different mutation rates, resulting in some organisms not surviving?
And the answer board says...
Definitely! Organisms more prone to mutations are more likely to develop harmful traits that prevent them from surviving. Organisms with lower mutation rates will see less harmful mutations, resulting in better survival.
Next question! Do organisms exhibit variation in their mutation rates?
And the answer board says....
The majority of mutations arise from errors in genome copying. Genes are copied by a protein that is also coded for in the genome! If that copying code varies, organisms will have a variety of accuracy when it comes to copying their DNA. That's variation!
Three down, two to go! Fourth: is the variation in mutation rate heritable?
Answer board says...
Yes! The protein for genome copying (called DNA polymerase) is heritable, because it is encoded for by genes! Whether a parent makes effective or mistake-ridden DNA polymerase, they're going to pass that trait down to their kids.
Fifth and Final question! Some variation in mutation rate is favored and leads to better survival. Are there circumstances were a high or low mutation rate would be adaptive?
Science (and your clueless host) says yes!
High mutation rates could be adaptive in environments that change frequently - an abundance of mutations would mean that beneficial mutations come about more quickly, and thus a population will adapt faster to environmental change.
Low mutation rates might be adaptive in environments that are very steady. Mutation is almost always negative, so if an organism already has a highly adapted form then their mutation rate might drop so as to minimize unwanted variation in the face of a steady environment (see how crocodiles and sharks have gone unchanged for millions of years).
Hey, we made it! Looks like mutation rate can be acted upon by natural selection! Congratulations to all who played along. Join us next week for another episode of-
Hi Madison, I also came to the conclusion that mutation rates are more likely to decrease as they evolve because mutations are generally harmful. I used the example of cancer in my blog post. Our cells didn't develop so many proofreading mechanisms and checkpoints for nothing!
ReplyDeleteGreat post, Madison! One thing that came to my mind is that there are some instances (though rare) where an ELEVATED mutation rate could be advantageous. Think about antibiotic resistance in bacteria. If the mutation rate stays low, then you're correct that there will likely be fewer deleterious mutations. But you'll also RAPIDLY die from the antibiotics. So having an increased mutation rate may harm you somewhat, but if those deleterious mutations don't QUITE kill you, they may still increase the fitness of the organism by also enabling it to survive by evolving resistance. It's all a delicate balance of positive and negative effects!
ReplyDeleteAnother great post, a solid 10/10. I also agree that the mutation rates can be acted on by natural selection and evolve. This was a fun read. :)
ReplyDeleteHi Madison! Your blogs are one of my favorites to read because you convey information in such a creative and funny way. I really like how you incorporated the postulates into this post and how those mutation rates work.
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