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Entire Genetic Sequence of Individual Human Sperm Determined

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  • Entire Genetic Sequence of Individual Human Sperm Determined

    http://www.sciencedaily.com/releases...0719132855.htm

    ScienceDaily (July 19, 2012) — The entire genomes of 91 human sperm from one man have been sequenced by Stanford University researchers. The results provide a fascinating glimpse into naturally occurring genetic variation in one individual, and are the first to report the whole-genome sequence of a human gamete -- the only cells that become a child and through which parents pass on physical traits.

  • #2
    Originally posted by tomcat View Post
    http://www.sciencedaily.com/releases...0719132855.htm

    ScienceDaily (July 19, 2012) — The entire genomes of 91 human sperm from one man have been sequenced by Stanford University researchers. The results provide a fascinating glimpse into naturally occurring genetic variation in one individual, and are the first to report the whole-genome sequence of a human gamete -- the only cells that become a child and through which parents pass on physical traits.
    Ninety-one individual haploid snapshots from 1 man--very cool!

    Now, hypothetically speaking, these would look different from phased paternal haploid genome views, postconception, of the same sperm that went on to join with ova and produce viable offspring, nu? Chromosomal crossover would insure that.

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    • #3
      Originally posted by jah View Post
      Ninety-one individual haploid snapshots from 1 man--very cool!

      Now, hypothetically speaking, these would look different from phased paternal haploid genome views, postconception, of the same sperm that went on to join with ova and produce viable offspring, nu? Chromosomal crossover would insure that.
      No, the sperm's DNA is phased by definition -- it has just one copy of each chromosome. The crossover occurs during the creation of the sperm, between the paternal and maternal chromosomes in the man who produced the sperm.

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      • #4
        Originally posted by Ann Turner View Post
        No, the sperm's DNA is phased by definition -- it has just one copy of each chromosome. The crossover occurs during the creation of the sperm, between the paternal and maternal chromosomes in the man who produced the sperm.
        Yes, true, the sperm is haploid. A phased paternal DNA sequence read for a given individual is also haploid, true?

        Thus, the crossover I meant was not in the creation of the gamete, but that that occurs at the hypothetical fertilization of an ovum--for each of the 91 sperm. *That* particular crossover would make a hypothetical view of the genome of the given sperm look different from the paternal DNA seq read for the given phased individual who resulted from the fertilized ovum.

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        • #5
          Originally posted by jah View Post
          Yes, true, the sperm is haploid. A phased paternal DNA sequence read for a given individual is also haploid, true?

          Thus, the crossover I meant was not in the creation of the gamete, but that that occurs at the hypothetical fertilization of an ovum--for each of the 91 sperm. *That* particular crossover would make a hypothetical view of the genome of the given sperm look different from the paternal DNA seq read for the given phased individual who resulted from the fertilized ovum.
          There's no crossover within the fertilized egg. The paternal and maternal chromosomes remain intact, just as they were found in the sperm or the egg before fertilization. The next generation of crossover occurs later, at the point in time when that fertilized egg has grown into an individual and creates its own eggs or sperm.

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          • #6
            Originally posted by Ann Turner View Post
            There's no crossover within the fertilized egg. The paternal and maternal chromosomes remain intact, just as they were found in the sperm or the egg before fertilization. The next generation of crossover occurs later, at the point in time when that fertilized egg has grown into an individual and creates its own eggs or sperm.
            Ann, I copy from Wikipedia, on the topic of "fertilisation":

            "When gametes first fuse at fertilisation, the chromosomes donated by the parents are combined, and, in humans, this means that (2²²)² = 17.6x10EE12 chromosomally different zygotes are possible for the non-sex chromosomes, even assuming no chromosomal crossover. If crossover occurs once, then on average (4²²)² = 309x10EE24 genetically different zygotes are possible for every couple, not considering that crossover events can take place at most points along each chromosome."

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            • #7
              Originally posted by jah View Post
              Ann, I copy from Wikipedia, on the topic of "fertilisation":

              "When gametes first fuse at fertilisation, the chromosomes donated by the parents are combined, and, in humans, this means that (2²²)² = 17.6x10EE12 chromosomally different zygotes are possible for the non-sex chromosomes, even assuming no chromosomal crossover. If crossover occurs once, then on average (4²²)² = 309x10EE24 genetically different zygotes are possible for every couple, not considering that crossover events can take place at most points along each chromosome."
              The use of the word parents here is confusing. It's not the parents of the fertilized egg -- it's the parents of the man who was creating the sperm and the parents of the woman who was creating the egg (or in other words, the grandparents of the fertilized egg).

              The three-generation demo Mendel family at 23andMe shows how this works. You can see them with a guest account if you don't have a 23andMe test. If you do have an account at 23andMe and don't see the Mendels, go to Account / Settings / Example Profiles.

              Then look at the Family Inheritance diagram for Grandpa and Grandma Fisher compared to the grandchildren (their daughter's children). One will look like a photographic negative of the other. Wherever there's a gap between Grandpa and Grandchild, you'll see the gap is filled in when you switch to the view with Grandma. The three children are different because their mother Lily (Fisher) Mendel used different portions of her parents' DNA in creating the eggs.

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