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What is germline mosaicism in sperm cells and egg cells?

2 fertility expert(s) answered this question

Germline mosaicism in reproductive cells - what does it mean for your fertility?

Germline mosaicism means that some oocytes or sperm have a gene mutation that may not be present in other body tissues such as the blood, which is typically used for genetic testing.

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Answer from the fertility expert:
Maria José Mendiola, Gynaecologist in Reproductive Medicine & Reproductive Genetics, Clínica Monterrico

Germline mosaicism is a relative fragment mechanism of written disease and provides an explanation for the increased pattern in cases where multiple affected offspring are born to clinically and phenotypically normal parents. It arises through the occurrence of a mutation, the noble in the germline cell or one of its precursors during the early embryonic development of the parent because metabolic divisions predominate in both aspartohensis or genes most germline mosaicism mutations are likely to be mitotic rather than the meiotic origin. In this case in all genetic conditions there is a risk of your mosaicism. Germline refers to those cells that can pass DNA from one generation to the next and the eggs from a woman and the sperm from a man germline mosaicism means that some sperms or eggs have a gene mutation that may not be present in other tissues of the body such as blood. In these cases the parent with germline mosaicism diseases would not have symptoms of, for example, some disorders but with past temptations onto a proportion of their children. Germline mosaicism is suspected when two or more offspring present with condition, a dominant condition, for example, when there is no family history of the condition as a mutation is a rare event it is likely that multiple affected siblings would be due to multiple new mutations occurring in the same gene, in the same family so, once an affected parents have one child with a genetic disorder, they will often be offered genetic testing. No mutations are identified, for example, in the parent’s blood, it is presumed that the child has a denomination or that the child inherited the mutation from a parent with germline mosaicism.

Answer from the fertility expert:
Douglas Lester, Co-Founder & Chief Scientific Officer, Fertility Genomics

Germline mosaicism means that it either affects the sperm or the ovum. During the development of the eggs in the ovum, you have a two cells stage before you produce lots of ovum. Unfortunately, in one ovum, you get a fertility gene mutated, but the other remains normal. They are the two progenitor cells that produce all the ovum after that. So half of the ovum is fertile, and half are infertile, and it’s a similar story with sperm.

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