Think about the following scenario: A child is diagnosed as having long QT syndrome, an autosomal dominant disease. However, neither of his parents is affected. This may be due to a new mutation in the embryo, which would explain the son having the disease with normal parents. Next, this de novo mutation could be inherited to off-spring of the child? or not?
And there are additional questions. Why do so many genetic tests performed by blood samples represent all germline mutations? Except for cell free DNA, blood cells are not germline cells. Therefore, the mutation found in the blood sample test may be a huge somatic mutation (except blood cancer). For example, for mutations that occurred early in embryo development, many cells may have been affected, and I think this might be in the form of somatic mosaicism. Doesn't it mean that it's a germline mutation if it's found at 50% or 100%?
I asked you a little more, is there only a family test (segregation test) that checks to see if it's a germline mutation?
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And you say, in other words, de novo mutations can occur in postzygotic embryos or by germline mutations in parents.
Then I want to go further and conclude. In this case, an autosomal dominant disorder was detected as a heterozygote on a blood test. If it occurs in the embryo after conjugation, two possibilities are conceivable.
It could happens a heterozygous allele in the whole cell of a postzygotic embryo, Or can occur in one of the cells as a homozygous mutation when there are only two cells in the early embryo. In the latter case, autosomal dominant mutation would be lethal, so the child is likely not lived.
So in conclusion, if I thought that the whole cell of the child had the heterozygous mutation of the long QT syndrome, it was probably the result of the parent's germline mutation.
Am I thinkin right?