The exact mechanism of fertilization could not be determined but the study stated that it was unlikely to be a case of polar body twinning.In 2019, a second case of sesquizygotic twins was reported and molecular evidence of the phenomenon was documented by Gabbett and Fisk. In this case, the twins shared 100% of their maternal chromosomes and 78% of their paternal genomic information. The authors postulate two sperm from the same man fertilized an ovum simultaneously. The chromosomes assorted themselves through heterogonesis to form three cell lines. The purely paternal cell line died out due to genomic imprinting lethality, while the other two cell lines, each conisiting of the same maternal DNA but only 50% identical paternal DNA, formed a morula which subsequently split into twins

Mirror image twins
Mirror image twins result when a fertilized egg splits later in the embryonic stage than normal timing, around day 9–12. This type of twinning could exhibit characteristics with reversed asymmetry, such as opposite dominant handedness, dental structure, or even organs (situs inversus). If the split occurs later than this time period, the twins risk being conjoined. There is no DNA-based zygosity test that can determine if twins are indeed mirror image. The term "mirror image" is used because the twins, when facing each other, appear as matching reflections. Language development
There have been many studies highlighting the development of language in twins compared to single-born children.
The voltage for half activation of these channels (V½) is shifted 13mV hyperpolarized compared to wild-type. Deactivation of these channels is also slowed drastically compared to wild-type. This results in neurons with longer after-hyperpolarizations and thus, a decreased maximal firing rate. Diagnosis
Treatment
Prognosis
There is no known prevention of spinocerebellar ataxia. Those who are believed to be at risk can have genetic sequencing of known SCA loci performed to confirm inheritance of the disorder. Footnotes
External links
GeneReviews/NCBI/NIH/UW entry on Spinocerebellar Ataxia Type 13