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An introduction to genetic mutations

AP.BIO:
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Created by Ross Firestone.

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  • blobby green style avatar for user Josh.Monkey.O
    What are some other examples of mutation-caused diseases?
    (7 votes)
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    • blobby green style avatar for user Carson Purnell
      Cystic fibrosis, haemochromatosis, sickle-cell anemia, muscular dystrophy, colour blindness, phenylketoneurea, type I diabetes, retinitis pigmentosa, haemophilia, albinism, dwarfism, Huntington's chorea, Jacob-cruetzfeldt prion disease, waardenburg syndrome, off the top of my head. Every genetic disease is a mutation, except for the few survival chromosomal disorders. Everything else has genetic influences, like every cancer, as well as obesity and various neurological diseases, like schizophrenia, Alzheimer's. and Parkinson's.
      (21 votes)
  • hopper jumping style avatar for user Sina917
    What is the importance of spontaneous mutation ?
    (5 votes)
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  • blobby green style avatar for user R P
    How are genetic mutations inherited?
    (5 votes)
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    • leaf red style avatar for user ALAAYOUSSEF92
      So genetic mutations that are inherited from our parents, are most likely due to a "RECESSIVE" mutation. Meaning that there" 2 bad copies" one from the mother and one from the father. Genetic mutation are MORE likely to show up when parents are relatives because there is a higher probability of have 2 copies from the mutated genes. Another situation is DOMINANT mutations, where a condition might develop if ONLY one copy of the gene showed up from either mom and dad. Hope this helps!
      (7 votes)
  • aqualine tree style avatar for user Ivy
    What is the relationship between mutations and the environment?
    (4 votes)
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    • leafers seedling style avatar for user TeresaD
      There is a baseline level of mutations arising from "random errors" in the normal cellular processes of DNA synthesis, mitosis and meiosis. "Mutagens" are chemical or physical agents that can cause increases in DNA mutations above the baseline level arising from random errors. Differences in your environment can expose you to different levels and types of mutagens. For example, UV radiation is a mutagen. If you are in an environment where there is more UV radiation, you may be at greater risk of mutations. The same could be said of dozens of other agents, such as different hazardous chemicals you may use in your workplace, chemicals found in air and water pollution that differ from place-to-place, etc.
      (4 votes)
  • stelly blue style avatar for user Morgan
    With sickle cell disease being a mutation, what about a person being heterozygous for a mutation (does not make sense)? At , when the father had sickle cell disease and they said that most likely one of his kids will have it, this is impossible because his mother does not have it (unless she is heterozygous for the mutation). But being heterozygous for a mutation does not make sense, you either have a mutation or you do not, right?
    (5 votes)
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  • mr pants purple style avatar for user Jake
    Just wanted to point out that at you drew Fe3+, which is found methemoglobin, and cannot bind to oxygen. Hemoglobin contains ferrous iron, which is Fe2+
    (5 votes)
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  • duskpin sapling style avatar for user Abby S
    Do Sickle Cells clot? Do they get clogged in capillaries or arteries? If they can could that cause a heart attack? Or would it just be pain in the chest area or wherever else they get stuck?
    (4 votes)
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    • piceratops tree style avatar for user Jen
      Good thinking, you're absolutely right in that sickle cells are more prone to coagulation due to their shape! The symptoms cause can actually happen more frequently and are more widespread than just heart attacks and chest pain; patients with sickle cell diseases can experience generalized acute/chronic pain, organ swelling (ex. spleen), or even loss of vision... all due to sickle cells clogging capillaries! :(
      (2 votes)
  • leaf green style avatar for user Sisay1
    At , it is said that mutations rise at the level of the DNA and not from the protein or RNA. When looking under the microscope, the blood of a person who has sickle cell anemia I had noticed not all the red blood cells are sickle shaped. Would that indicate not all of the HB proteins are mutated? and thus a mutation rising at the level of protein or RNA?
    (2 votes)
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    • blobby green style avatar for user jayl03
      the mutation is still at the DNA level (i believe its a single base pair mutation that causes the red blood cells to be sickle shaped). the reason why only half of the red blood cells are sickle shaped is because anemia's pattern of inheritence is considered "codominant." codominance is noticeable when an individual is heterozygous for a disease, and their phenotype will be half the mothers and half the fathers. another example of codominance is blood types. for example lets say a mother has A type blood and is homozygous AA, the father has B type blood and is BB. the child will probably be AB. if you were to look at a sample of her blood under a super sophisticated microscope, half of her blood cells would have A antigens and the other half would have B antigens.

      so the anemic pt's blood you were looking at was probably heterzygotic for anemica, showing phenotypes of both normal red blood cells and sickle shaped red blood cells.
      (2 votes)
  • duskpin ultimate style avatar for user Akshi
    Persons suffering from sickle cell anemia normally do not suffer form malaria. why is it so?
    (1 vote)
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  • leafers tree style avatar for user Yamil Crespo
    What is the difference between synonymous mutation and silent mutation?
    (1 vote)
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Video transcript

Voiceover: Today I'm going to give you a quick introduction into genetic mutations. But first, let's go over the central dogma of molecular biology, which is just the idea that genetic information in a cell is formed in the form of DNA. This DNA is used to generate complimentary RNA through a process called transcription. That RNA is then used to synthesize a corresponding protein through the process of translation. Looking at a quick example, our short DNA strand here will be used to generate an RNA stand. Remember that A pairs with U or T and C pairs with G. Next, our RNA will be used to generate protein through translation. Remember that during this process, RNA nucleotides are read in groups of three, called codons, in order to generate corresponding amino acids. Just very generally, we say that mutations >>have the affect of making this synthesized protein not turn out quite right. I'm going to give a quick shout-out to sickle-cell disease, which is an example of a disease that's caused by a genetic mutation. You may remember that there is a protein in red blood cells called hemoglobin, which we can also call Hb. Hemoglobin in a protein that coordinates to iron ions in order to hold onto oxygen molecules and transport them throughout the body. The mutation that causes sickle-cell disease results in a mutated form of hemoglobin called HbS being formed, where the S is for the word sickle. The difference between normal hemoglobin and HbS is that one glutamate amino acid residue is being replaced with a valine amino acid residue. This small change results in all of these mutated HbS proteins aggregating together in a red blood cell, which makes it very difficult for that red blood cell to transport oxygen effectively. Just a side point, remember that red blood cells are initially generated from hematopoietic stem cells through a process called hematopoiesis. Where are mutations found, and how do they come up in the first place? Let's look at a couple of different possible mistakes that could lead to an incorrectly produced protein. First, we'll see what happens if a cell makes a mistake during translation. We'll stick with our example of sickle-cell disease from before. Let's say that we have this sample piece of DNA with three nucleotides from the gene coding for hemoglobin. This DNA is transcribed to form the complimentary RNA sequence GAG. That GAG would normally correspond to a glutamate residue during translation, but a mistake during translation might lead to a valine residue being translated instead to produce the mutated hemoglobin associated with sickle-cell disease. But notice that if a mutation happens during translation, the cell will only produce one mutated hemoglobin, or HbS, for each overall mistake. Since cells are making tons and tons of hemoglobin, just one mutated protein might not have that big of an effect on the cell. So we can say that mistakes during translation probably don't cause mutations like the one associated with sickle-cell disease. Next, we'll look at mistakes during transcription. Again, we have our CTC piece of DNA, which would normally make GAG on RNA, but maybe a mistake occurs which leads to the transcription to a GUG instead, which would then code for the valine associated with mutated hemoglobin. If this mistake occurred, the cell would only make a few mutated hemoglobins for each mistake since an individual strand of messenger RNA will only be translated a couple of times before being degraded. >>So we can say that mistakes during transcription probably don't cause mutations like the one associated with sickle-cell disease. Finally, we'll look at mistakes in the DNA strand. If our CTC in DNA is mistakenly turned into a CAC, then our corresponding RNA from transcription will be changed and ultimately a valine would be produced instead of a glutamic acid. Now, since a cell's DNA stores all of its genetic information, that mistake would lead to all future hemoglobins produced from that gene being mutated. So overall, we can say that mutations will usually result from mistakes in a cell's DNA and not from the RNA or the protein. So where do these types of mutations come from? There are two ways a person can get a genetic mutation. The first is that they inherit it from their parents. Remember that DNA is passed down from parents to offspring, so if we have a mutated father here, then there's a good chance that at least one of his kids will inherit that mutated gene the same way that the child might inherit any amount of that parent's DNA. The other possibility is that the mutation will come on spontaneously, which is where a person suddenly gets a mutation in their DNA without their parents having had the same mutation. Spontaneous mutations can come from many different sources, with just a few examples being from DNA replication errors, environmental factors like certain poisons. It's also possible that genetic mutations can come on entirely randomly. What did we learn? First we learned that mutations originate at the DNA level, and not the RNA or protein level. The effects of the mutation, like the example we gave of sickle-cell disease, are found with problems with the proteins that are ultimately expressed by the mutated DNA. Now, like every rule, there are a couple of exceptions to this one, but we can say that the effects of a mutation are usually found at the protein level. Finally, we learned that mutations are either inherited from a parent, or come on entirely spontaneously.