Table I.
Example of short tandem repeat informativity results for an autosomal dominant disorder.
| Affected male partner | Unaffected female partner | Informativity | ADO detection in the embryo | Detection of maternal contamination | Additional info on monosomy/trisomy | Comments | Recommendation for PGT-M (ranking1) |
|---|---|---|---|---|---|---|---|
| 124–126* | 120–122 | Fully informative | Yes | Yes | Yes | 4 distinctive parental alleles | Preferred marker (1) |
| 124–126* | 120–120 | Informative | Yes | No | Partially | 3 distinctive parental alleles, the affected partner is heterozygous, the unaffected partner is homozygous for a third allele. The wild-type allele is a unique allele. | Good marker (2) |
| 124–126* | 120–126 | Partially informative | Partially | Partially | Partially | 3 distinctive parental alleles, both partners are heterozygous, but the mutant allele of the affected partner is shared with an allele of the unaffected partner. The wild-type allele is a unique allele. Unaffected embryos (124–120 or 124–126) can be distinguished, as well as one genotype of affected embryos (126*-120). The second genotype of affected embryos is homozygous (126*-126), therefore it is uncertain if both paternal and maternal alleles are present. | Usable marker (3) |
| 124–126* | 126–126 | Partially informative | Partially | No | Partially | 2 distinctive parental alleles, the wild-type allele is a unique allele; the marker yields only information about the wild-type allele and is therefore limited in use | Usable marker (4) |
| 124–126* | 120–124 | Partially informative | Partially | Partially | Partially | 3 distinctive parental alleles, both partners are heterozygous, but the wild-type allele of the affected partner is shared by the unaffected partner. One genotype of unaffected embryos (124–120) can be distinguished from affected embryos (126*-120 or 126*-124); the second genotype of unaffected embryos is homozygous (124–124), therefore it is uncertain if both paternal and maternal alleles are present. | Usable marker (5) |
| 124–126* | 124–124 | Partially informative | Partially | No | Partially | 2 distinctive parental alleles, the mutant allele is a unique allele; the marker yields limited information about the mutant allele. | Usable marker (6) |
| 124–126* | 124–126 | Partially informative | Partially | No | No | 2 distinctive parental alleles, no unique alleles; the marker yields very limited information (to be used in combination with other markers) | Usable marker (7) |
| 126–126* | Any genotype | Non-informative | No information about the monogenic disorder but may yield information on parental contribution. | Not recommended |
1The utility of the markers is ranked from very good (1) to very low (7)
The pathogenic allele is indicated with * after validation of segregation analysis with a suitable reference.
ADO: allele drop-out, PGT-M: preimplantation genetic testing for monogenic/single-gene defects