PEDIGREE
Arabian horse SCID pedigree — autosomal recessive
This Arabian horse pedigree chart traces severe combined immunodeficiency (SCID), an autosomal recessive condition, across three generations. Two carrier founders pass the allele to a carrier mare, and when she is bred to a carrier stallion their colt is born with SCID and dies within months.
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CASE ANALYSIS
Scenario
An Arabian breeding program traces an SCID foal back through its carrier parents to plan safer matings.
Key decisions
- Only the foal in generation III is affected: SCID foals die within months, so no affected horse appears as a parent.
- The foal is affected because both its dam and sire are carriers, each passing one copy of the recessive allele.
- The generation-I founders are both carriers, which explains carrier status in two of their three offspring.
- The deceased mark on the proband records the outcome breeders need to see at a glance.
When to reuse this
Use this layout to explain a recessive condition in a breeding record. Carrier status should come from a DNA test, and mating decisions belong with a veterinarian.
FAQ
Frequently asked questions
Is Arabian SCID autosomal recessive?
Yes. A foal is affected only when it inherits the allele from both its dam and its sire.
Why are both parents of the affected foal carriers?
Affected foals do not live long enough to breed, so the allele is passed on by healthy carriers. Two carriers have a one-in-four chance of an affected foal with each mating.
Can an unaffected horse be a carrier?
Yes. Carriers are clinically normal; only a DNA test tells a carrier from a clear horse.
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pedigree-arabian-horse-scid