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Current time:0:00Total duration:4:11

The effects of mutations

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Video transcript

so today we're going to talk about the overall effects of a genetic mutation and how mutations impacts the affected organism as a whole but first I want to review the central dogma of molecular biology and how genetic information in a cell is stored in the form of DNA which is then transcribed to form RNA which is then translated to form protein now nucleotides from DNA are transcribed to their complimentary forms on RNA which are then read as codons or groups of three to code for specific amino acids in a larger protein now if you mutate one of the nucleotides on DNA lecturing a thymine base into an adenine base then that will affect the RNA sequence and ultimately the protein that follows so we say that mutations are generally mistakes in a cell's DNA that lead to abnormal protein production so our mutations good or are they bad and what kind of a factor they have on the affected organism well there isn't really a good answer to this question at all and there are many many different types of mutations out there that can result in big structural changes like the little pictures I've drawn out here or may result in little subtle changes that might go completely unnoticed it's very difficult to call a mutation good or bad though since it really depends on a huge number of things including the environment that the organism lives in so let's look at an example of a good mutation so the bacteria streptococcus pneumoniae is the bacteria that you typically see associated with pneumonia and one of the more popular treatments for pneumonia is giving the infected person an antibiotic like penicillin which would help kill all of the bacteria and get rid of the disease but sometimes you can find some mutated streptococcus bacteria that will have a special trait that makes them resistant to penicillin and now penicillin won't kill them as easily as it will kill the bacteria without the mutation now we call this a good mutation because the bacteria are living in a human host where they're likely to encounter this deadly penicillin and being resistant to antibiotics like penicillin would then be beneficial to the bacteria and just to clarify I'm calling this a good mutation for the bacteria not really for the human infected since it'll be harder for them to get rid of the bacteria that are resistant to certain so now let's look at an example of a bad mutation so the disease cystic fibrosis is usually caused by a mutation in the CFTR gene now I'm not really going to go into detail about how this mutation actually hurts you but I'll leave you with the idea that what it does is it makes the mucus that you'd find in a person's lungs really really thick which makes it really hard for people affected with the disease to breathe so in general we can say that the de mutation causing cystic fibrosis would be a quote unquote bad mutation but mutations aren't strictly good or strictly bad in fact there are some mutations that can cause some favorable and some disadvantageous effects sickle-cell disease results from a mutation in a protein called hemoglobin that you'd find in red blood cells and this mutation terms hemoglobin into a much less functional form which we'll call HBS and it's much less efficient at moving oxygen around the human body but another effect of sickle-cell disease is that it makes the disease person less susceptible to malaria now malaria is a parasite that grows and multiplies in red blood cells and can have a lot of nasty effects on the host organism and the malaria parasite can't really grow as well in red blood cells that are affected with sickle-cell disease so in this case the mutation associated this disease has one bad effect which is that the HBS isn't as good as carrying oxygen around the body but also a good effect in that it makes it less likely that the disease person will be affected by malaria since they can't grow as well in the humans red blood cells so what did we learn well first we learn that the effects of the mutation will usually but not always appear at the protein level there are some exceptions to this rule and second we learn that genetic mutations can have advantageous deleterious or neutral effects depending on the type of mutation the environment that the affected organism lives in as well as a multitude of other factors