Splashed White Overo (SWO)
Summary
Splashed White Overo (SWO) is term applied to mutations in different genes that are dominant modifiers of coat color, producing white patterning. The variants responsible for two forms of Splashed White Overo are recessive embryonic lethals. Embryos homozygous for either of these mutations cannot complete development.
Splashed White 2 (SW2) results from a mutation in PAX3 (PAX3-C70Y) and is seen in Quarter Horses. Splashed White 3 (SW3) results from a mutation in MITF (MITF-C280Sfs*20), and is seen in Quarter Horses.
Date of Last Update: 04/04/2016
SW2
Back to TopSummary
Splashed White Overo (SWO) is term applied to mutations in different genes that are dominant modifiers of coat color, producing white patterning. The variants responsible for two forms of Splashed White Overo are recessive embryonic lethals. Embryos homozygous for either of these mutations cannot complete development.
Splashed White 2 (SW2) results from a mutation in PAX3 (PAX3-C70Y) and is seen in Quarter Horses.
Date of Last Update: 04/04/2016
Date of Last Update: 08/02/2016
Results
Understanding the Results
Results of the genetic test for Splashed White 2 (SW2) are presented as shown below.
| Splashed White 2 (SW2) | ||
|---|---|---|
| N/N | Clear | This horse tested negative for SW2. |
| N/SW2 | Carrier | Both the normal and mutant alleles are present. This horse is positive for the SW2 mutation but will not develop symptoms. |
Disease Name and Genes
Splashed White 2 (SW2) has a dominant effect on coat color (Splashed White) and is a recessive embryonic lethal resulting from a G to A substitution that causes a nonconservative amino acid substitution in the DNA-binding domain of the transcription factor PAX3 (PAX3-C70Y).
Inheritance
Splashed White 2 (SW2), caused by the PAX3-C70Y variant, is a recessive embryonic lethal. Carriers are not affected, although they have the coat color phenotype. The recessive allele is commonly abbreviated as SW2, with the dominant wild-type allele abbreviated as N.
Carriers of the recessive allele (N/SW2) have no symptoms of the disease. If two carriers are bred, each foal has a 25% chance of having two copies of the normal allele (N/N), a 50% chance of being a carrier (N/SW2), and a 25% chance of being an inviable embryo (SW2/SW2).
If a carrier of the recessive allele (N/SW2) is bred to a normal horse (N/N), each foal has a 50% chance of having two copies of the normal allele (N/N) and a 50% chance of being a carrier (N/SW2).
Citations
SW3
Back to TopSummary
Splashed White Overo (SWO) is term applied to mutations in different genes that are dominant modifiers of coat color, producing white patterning. The variants responsible for two forms of Splashed White Overo are recessive embryonic lethals. Embryos homozygous for either of these mutations cannot complete development.
Splashed White 3 (SW3) results from a mutation in MITF (MITF-C280Sfs*20), and is seen in Quarter Horses.
Date of Last Update: 04/04/2016
Date of Last Update: 08/02/2016
Results
Understanding the Results
Results of the genetic test for Splashed White 3 (SW3) are presented as shown below.
| Splashed-White 3 (SW3) | ||
|---|---|---|
| N/N | Clear | This horse tested negative for SW3. |
| N/SW3 | Carrier | Both the normal and mutant alleles are present. This horse is positive for the SW3 mutation but will not develop symptoms. |
Disease Name and Genes
Splashed White 3 (SW3) has a dominant effect on coat color (Splashed White) and is a recessive embryonic lethal resulting from a deletion that causes a frameshift in the transcription factor MITF (MITF-C280Sfs*20). The frameshift causes the alteration of 20 amino acids before a stop codon is reached at position 300 of the 526 amino acid MITF protein. The resultant truncated MITF protein lacks the DNA binding domain.
Inheritance
Splashed White 3 (SW3), caused by the MITF-C280Sfs*20 variant, is a recessive embryonic lethal. Carriers are not affected, although they have the coat color phenotype. The recessive allele is commonly abbreviated as SW3, with the dominant wild-type allele abbreviated as N.
Carriers of the recessive allele (N/SW3) have no symptoms of the disease. If two carriers are bred, each foal has a 25% chance of having two copies of the normal allele (N/N), a 50% chance of being a carrier (N/SW3), and a 25% chance of being an inviable embryo (SW3/SW3).
If a carrier of the recessive allele (N/SW3) is bred to a normal horse (N/N), each foal has a 50% chance of having two copies of the normal allele (N/N) and a 50% chance of being a carrier (N/SW3).
