What genetic and reproductive counseling would you indicate to a 30-year-old woman who consults because she is a carrier of a premutation in the FMR1 gene, responsible for Fragile X syndrome, and who wishes to have offspring. Point out the correct answer:
Another classic MIR, asked in 2019 and in 2017, fragile X syndrome. Also, on the same concept as question 44, the phenomenon of genetic anticipation. Triplet expansion diseases, such as this one, can have the anticipation phenomenon whereby females with premutations (between 55-200 repeats) can have children with full mutations (more than 200 repeats of the triplet) and more obvious, more severe and/or earlier clinical, in both males and females (Fragile X syndrome, early ovarian failure, tremor/ataxia associated with Fragile X).
All her male children will be carriers and, therefore, will manifest the disease.
There is a phenomenon of genetic anticipation, so their offspring will present more severe and earlier symptoms.
Preimplantation genetic diagnosis for sex selection of embryos by fluorescence in situ hybridization (FISH) is the best option for healthy offspring.
50% of her daughters will be carriers, but will not present clinical manifestations of the disease.
Triplet expansion diseases, such as this one, can have the anticipation phenomenon whereby females with premutations (between 55-200 repeats) can have children with full mutations (more than 200 repeats of the triplet) and more obvious, more severe and/or earlier clinical, in both males and females (Fragile X syndrome, early ovarian failure, tremor/ataxia associated with Fragile X).