Help with DNA report?

How can you tell if DNA results are for a parent and child as compared to a brother to sibling?

1 Answer

  • topaz
    Lv 7
    9 years ago
    Favorite Answer

    A parent's with one of their children would have 50% of the alleles in common. The child would get 1/2 of their alleles from each parent, so unless you take into account crossing over or spontaneous mutations, half the alleles would be identical.

    In the case of two siblings, even though they have the same biological parents, the alleles could align different ways during meiosis, so they could share more or less than 1/2 of the same alleles. The only exception would be if they were identical twins. If that doesn't sound possible, do an example. Say both parents are hetero for 5 chromosomes - AaBbCcDdEe x AaBbCcDdEe. Child 1 could get the recessive alleles from both parents (aabbccddee) and child 2 could get all the dominant ones (AABBCCDDEE) so they would have NO alleles in common. A 3rd child could be born with a mix, and their genes could be AAbbCCddEE - this child would have 2 alleles (40%) in common with the oldest child and 3 alleles (60%) in common with the second child.

    If I'm reading too much into the question, when the DNA sample is taken and the electrophoresis done, each person would have their DNA in a separate column (called a lane). Whoever takes the samples and puts it in the gel would make a key to say which lane belonged to which person.

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