Have you ever heard a story where a child has a genetic disease but neither of the biological parents, and none of the more distant relatives, have the disease? How does that work? Well, even though our cells make identical copies of themselves through mitosis, if there is a mutation that is copied into many cells, then this means someone's body could have non-identical cells: some with a mutation and some without a mutation. These people are called mosaics. If mutated cells are found in the gametes (eggs or sperm), then they are passed on to children. Recently, the results of the largest study conducted yet on mosaicism - specifically on diseases passed on to children - were published. It included 100 families, and scientists confirmed that four parents were mosaics. However, many more were probably mosaics, even if they couldn't detect it, because only blood cells were sampled and not muscle or other tissue cells, and they were only capable of finding genetic deletions instead of insertions or changes in DNA.
In the future, scientists hope to be able to test for this, so parents will know if they will pass on a disease to their children.
http://www.nytimes.com/2014/07/31/science/having-more-than-one-set-of-dna-carries-legacy-of-risk.html
In the future, scientists hope to be able to test for this, so parents will know if they will pass on a disease to their children.
http://www.nytimes.com/2014/07/31/science/having-more-than-one-set-of-dna-carries-legacy-of-risk.html