What are the main options in preimplantation genetic testing (PGT) and what does each detect?

• A. PGT-A detects aneuploidy; PGT-M detects monogenic disorders; PGT-SR detects structural chromosomal rearrangements.
• B. PGT-A detects maternal blood type; PGT-M detects carrier status; PGT-SR detects facial features.
• C. PGT-A detects single-gene disorders; PGT-M detects chromosomal translocations; PGT-SR detects metabolic diseases.
• D. PGT-A detects mitochondrial DNA variations; PGT-M detects environmental exposure effects; PGT-SR detects epigenetic modifications.

Answer: (A)

In preimplantation genetic testing, there are three main goals, each targeting a different genetic issue that can affect embryos. The first modality screens for aneuploidy, meaning it checks whether embryos have the correct number of chromosomes across all chromosomes. The second modality looks for known single-gene (monogenic) disorders when there is a familial mutation, so it can identify embryos that do not carry that specific pathogenic variant. The third modality detects structural chromosomal rearrangements, such as translocations or large deletions/duplications, which can lead to unbalanced genetic content in the embryo.

This combination is best described as: PGT-A for aneuploidy detection, PGT-M for monogenic disorders, and PGT-SR for structural rearrangements. Context helps: screening for aneuploidy aims to improve implantation chances and reduce miscarriage due to chromosomal number problems; testing for monogenic disorders targets specific inherited mutations; assessing structural rearrangements helps avoid embryos that would result in unbalanced chromosomal content.

Other options mix up what each option detects—for example, maternal blood type, facial features, environmental effects, or epigenetic changes are not the focus of these PGT modalities.