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Thread: Crossing-over

  1. #1 Crossing-over 
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    Is crossing-over so strong and important that can make from small parents big children ?? And is it proved ??


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  3. #2 Re: Crossing-over 
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    Quote Originally Posted by Siemowit
    Is crossing-over so strong and important that can make from small parents big children ?? And is it proved ??
    Huh? You mean "Crossing over with John Edwards" crossing over? Then no, no proof exists that is accepted by the scientific community. (that I know of )


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    And is smaller change more possible than greater change ??
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    CROSSING OVER IN GENETICS "crossing over, process in genetics by which the two chromosomes of a homologous pair exchange equal segments with each other" discovered by Thomas Morgan not by John Edwards
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    Lol, ok. I haven't a clue. I was thinking of somethin WAY different
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

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    Yes, crossing over is very important. Yes, it can make big children from small parents.

    I'm speculating based on my knowledge, btw. 8)

    Edit: to add, I've seen some 'unlikely' offspring before (like tall kids from short parents, white kids from black parents, etc). It all depends on your family's genetic background.
    Whence comes this logic: no evidence = false?

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    This is a seriously misguided line of thought! Crossing over simply shuffles the genes on a pair of homologous chromosomes, it does not alter the actual genes present, and so cannot change the genetic characteristics of a species.
    Knowledge of evolution may not be strictly useful in everyday commerce. You can live some sort of life and die without ever hearing the name of Darwin. But if, before you die, you want to understand why you lived in the first place, Darwinism is the one subject that you must study.

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  9. #8  
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    Quote Originally Posted by adamd164
    Crossing over simply shuffles the genes on a pair of homologous chromosomes, it does not alter the actual genes present, and so cannot change the genetic characteristics of a species.
    Correct. But if your parents have certain recessive genes, it may become expressible during crossing-over.

    So it's not that new genes become introduced, it's just that subdued (for lack of better word) genes become expressed; hence short kids from tall parents and vice versa.
    Whence comes this logic: no evidence = false?

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  10. #9  
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    Quote Originally Posted by scientstphilosophertheist
    Quote Originally Posted by adamd164
    Crossing over simply shuffles the genes on a pair of homologous chromosomes, it does not alter the actual genes present, and so cannot change the genetic characteristics of a species.
    Correct. But if your parents have certain recessive genes, it may become expressible during crossing-over.

    So it's not that new genes become introduced, it's just that subdued (for lack of better word) genes become expressed; hence short kids from tall parents and vice versa.
    Crossing over just produces gametes with genes in a different order than in the parents somatic cells. It doesn't in any way alter the expressibility of those genes. If parent cell has genes A (dominant) and a (recessive), then the chances of a gamete containing a, the recessive allele, are one in two, irrespective of crossing over taking place.
    Knowledge of evolution may not be strictly useful in everyday commerce. You can live some sort of life and die without ever hearing the name of Darwin. But if, before you die, you want to understand why you lived in the first place, Darwinism is the one subject that you must study.

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  11. #10  
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    Quote Originally Posted by adamd164
    Quote Originally Posted by scientstphilosophertheist
    Quote Originally Posted by adamd164
    Crossing over simply shuffles the genes on a pair of homologous chromosomes, it does not alter the actual genes present, and so cannot change the genetic characteristics of a species.
    Correct. But if your parents have certain recessive genes, it may become expressible during crossing-over.

    So it's not that new genes become introduced, it's just that subdued (for lack of better word) genes become expressed; hence short kids from tall parents and vice versa.
    Crossing over just produces gametes with genes in a different order than in the parents somatic cells. It doesn't in any way alter the expressibility of those genes. If parent cell has genes A (dominant) and a (recessive), then the chances of a gamete containing a, the recessive allele, are one in two, irrespective of crossing over taking place.
    Oh... really? I'm a little rusty. During what process do the different combinations take place?

    I remember that being during crossing over. But, like I said, I'm a little rusty.
    Whence comes this logic: no evidence = false?

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  12. #11  
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    Quote Originally Posted by scientstphilosophertheist
    Oh... really? I'm a little rusty. During what process do the different combinations take place?

    I remember that being during crossing over. But, like I said, I'm a little rusty.
    Crossing over is recombination of genes, that much is correct, but it doesn't in any way alter expressibility or likelihood of recessive genes being passed on. Have a look at this
    Knowledge of evolution may not be strictly useful in everyday commerce. You can live some sort of life and die without ever hearing the name of Darwin. But if, before you die, you want to understand why you lived in the first place, Darwinism is the one subject that you must study.

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    Quote Originally Posted by adamd164
    Quote Originally Posted by scientstphilosophertheist
    Oh... really? I'm a little rusty. During what process do the different combinations take place?

    I remember that being during crossing over. But, like I said, I'm a little rusty.
    Crossing over is recombination of genes, that much is correct, but it doesn't in any way alter expressibility or likelihood of recessive genes being passed on. Have a look at this
    What recombination does do is change the position of genes and alleles. The position of a certain gene and what genes are near it can have a significant effect on how it and/or other genes are expressed. Many controlling DNA elements that effect transcription are located either upstream or downstream of the gene itself. By switching these alleles around you can in fact generate phenotypic effects that may not have necessarily been present in the parents.

    I'm not too clear on how height is determined genetically, so I can't speak as to how that might be effected by recombination.
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