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Post by sugarfreejazz on Oct 4, 2011 18:21:27 GMT -5
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Post by Admiral Lithp on Oct 4, 2011 18:34:09 GMT -5
I'm still wondering if I have this whole archaeopteryx shit right.
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Post by The_L on Oct 4, 2011 19:07:13 GMT -5
Okay, but that doesn't really answer her question. Not that I know the answer. I really don't know if more disorders are developmental or genetic. Well, I remember a big deal some years ago about frogs with misshapen/missing hind legs. Like in the early 00s people thought it was radiation or pollution making the genes mutate, but it turned out to be caused by aquatic insect larvae biting the leg-buds off of small tadpoles. Since Down Syndrome is caused by an extra chromosome, I don't think that can be called a genetic mutation, since it's not a change in allele frequency - it's a mistake in the originating zygote. Polydactyly IS genetic and inheritable, so it might be a true mutation. However its effect on its carriers is largely neutral. An extra chromosome IS a mutation. The fact that it happened before the egg was fertilized doesn't make it less of a mutation. Also, there's cri du chat--a serious genetic disorder caused by a repeating segment in chromosome 5 (I think it's 5--I honestly haven't looked this up in nearly a decade).
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Post by Admiral Lithp on Oct 4, 2011 19:09:59 GMT -5
Cliffhanger Ending.
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Post by A Reasonable Rat on Oct 4, 2011 19:54:43 GMT -5
Down Syndrome is a mutation. Mutations are changes in the genome and Downs as you know is caused by an extra chromosome. Chromosomes are part of the genome. I'm also a bit confused why you'd mention that polydactylyism is neutral. Oh, because the OP topic includes claims that mutations are more or less always detrimental. Also the definition of mutation is an issue here. I'm of the belief that mutations in evolutionary terms, must be within the alleles. An extra chromosome almost always impairs reproduction, and therefore is excluded from the evolutionary process.
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Post by SimSim on Oct 4, 2011 21:14:12 GMT -5
You can believe what you like, but that doesn't make it correct. An extra copy of a chromosome is a mutation.
Judging from this sentence, "An extra chromosome almost always impairs reproduction, and therefore is excluded from the evolutionary process." You seem to be operating under the premise that a mutation needs to be passed on to the next generation, it doesn't. Go read about somatic mutations.
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Post by A Reasonable Rat on Oct 4, 2011 22:45:44 GMT -5
You can believe what you like, but that doesn't make it correct. An extra copy of a chromosome is a mutation. Judging from this sentence, "An extra chromosome almost always impairs reproduction, and therefore is excluded from the evolutionary process." You seem to be operating under the premise that a mutation needs to be passed on to the next generation, it doesn't. Go read about somatic mutations. 'And therefore is excluded from the evolutionary process'. A mutation doesn't become an evolutionary factor unless it gets passed on. The topic is about evolution. An extra chromosome may be a mutation, but it's not evolution, it's not a genetic mutation that leads to species change.
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Post by sugarfreejazz on Oct 4, 2011 22:52:09 GMT -5
Except that you said "I don't think that can be called a genetic mutation, since it's not a change in allele frequency." & "Also the definition of mutation is an issue here. I'm of the belief that mutations in evolutionary terms, must be within the alleles." Sim is explaining why your definition (stated by you) for mutations does not work. It is not solely attributed to "passing on" regardless of topic.
Edit: If you're starting off with the wrong definitions it can skew your understanding and ultimately lead to the incorrect conclusion. My link better explains mutation terminology and definition.
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Post by Random Guy on Oct 4, 2011 23:35:30 GMT -5
I'm still wondering if I have this whole archaeopteryx shit right. It was originally thought to be ancestral to birds. It is now considered to be ancestral to velociraptors instead. This didn't come to light until a new dinosaur, Xiaotingia, was found and compared to Archaeopteryx.
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Post by A Reasonable Rat on Oct 5, 2011 11:49:55 GMT -5
Except that you said "I don't think that can be called a genetic mutation, since it's not a change in allele frequency." & "Also the definition of mutation is an issue here. I'm of the belief that mutations in evolutionary terms, must be within the alleles." Sim is explaining why your definition (stated by you) for mutations does not work. It is not solely attributed to "passing on" regardless of topic. Edit: If you're starting off with the wrong definitions it can skew your understanding and ultimately lead to the incorrect conclusion. My link better explains mutation terminology and definition. I'm sorry, but I still have to disagree, after reading that link, and one that it links to for more information, and some articles on Trisomy, they all appear to back up my assertion that Trisomy is not technically a genetic mutation. The link you shared says that mutation can be large sections of a chromosome, but no mention of duplication of entire chromosomes is made within the article's definition of what genetic mutation is. Also the article on Trisomy describes it as an abnormal duplication, but the word 'mutation' doesn't come up. Mutation is considered a change in the DNA sequence, but Trisomy doesn't (typically) change the contents of the chromosome, it just copies it in its entirety. So I still don't think spontaneous chromosome duplication is genetic mutation (and I'm torn on chromosome fusion, which is a major topic in human evolution, but hasn't addressed whether or not that fusion has affected the contained DNA.) I am perfectly willing to change my interpretation, I just haven't seen anything that's made me feel I should. Edit: en.wikipedia.org/wiki/Chromosome_abnormalityTrisomy is not included in the descriptions of genetic mutation, but classified as 'Aneuploidy'. learn.genetics.utah.edu/archive/mutations/index.htmlMutations are described as changes to the information inside the chromosome. anthro.palomar.edu/abnormal/abnormal_4.htmTrisomy can be the result of a mutation in the parent which causes them to produce extra chromosomes in their reproductive cells, but the extra chromosome itself isn't classified as a mutation.
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Post by Vene on Oct 5, 2011 12:28:22 GMT -5
Christ, this is a stupid discussion. From wiki "In molecular biology and genetics, mutations are changes in a genomic sequence," an addition of a whole chromosome is a change in a genomic sequence, it's a bloody mutation. Hell, you just gave one with that definition and I don't know what kind of contorted reasoning you need to say that having three sets of alleles instead of two isn't a change in DNA sequence.
Rat, for whatever reason you're trying to redefine words in ways that make no sense. It's a genetic anomaly, it's a mutation. But, because of the special circumstances surrounding trisomy (or any other type of aneuploidy) it's often talked about separately.
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Post by A Reasonable Rat on Oct 5, 2011 13:01:19 GMT -5
Forgive me, I have no particular agenda, just an OCD/aspie need to totally clear this up. If you saw somewhere in the links I've provided a definition of trisomy as mutation, tell me where, because I missed it.
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Post by Vene on Oct 5, 2011 14:18:08 GMT -5
It doesn't mention trisomy specifically, because it doesn't have to. Trisomy is a change in genomic sequence, that is the definition of a mutation, therefore it is a mutation. It is also a chromosomal disorder. It is also a developmental disorder. It is also a variant of aneuploidy. It is also a non-disjunction event. It is all of these.
ETA: A major part of science is being able to correlate and connect various bits of data and not getting so hung up on definitions and categories, especially in biology where absolutely everything has some sort of exception.
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Post by MaybeNever on Oct 5, 2011 14:45:57 GMT -5
And a major part of autism is getting hung up on definitions, perseveration of thought, and concretism in thinking. Isn't Oriet an aspie too?
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Post by Magnizeal on Oct 5, 2011 15:01:33 GMT -5
But once you know the definition, especially if it's been told to you by someone who knows more than you, you need to adjust. Oriet and I can adjust. And if the definition of 'mutation' is change in the genetic sequence, and if trisomy is changing the genetic sequence, well then, guess what?
And just because Rat is hung up on definitions and all that doesn't give her an excuse in this case, because the nature of what she's looking at needs more flexibility. Which has now been pointed out. So, as I said, it's time to adjust. Might it be hard and distressing to adjust? Sure! But that's reality, and if I sound like a heartless bastard, I remind all that I've had to do this myself, more than once.
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