Skip to content
Login Register

#polydactyly

2 public questions tagged with this topic.

Limb Development -l

Which gene mutation is associated with polydactyly?

Polydactyly reflecting supernumerary digits often arises from dysregulation of SHH-Gli3 and distal Hox networks controlling digit periodicity. Mutations in HOXD13, particularly polyalanine tract expansions, cause synpolydactyly with fused extra digits due to altered transcriptional regulation of autopod patterning and ectopic activation of anterior Gli3 processing leading to broadened SHH targets. Tbx4 dictates hindlimb identity, Pax6 eye development, FGF10 limb initiation. HOXD13 normally limits digit number controlling interdigital proliferation and termination timing, thus mutation disrupts fine-tuning leading to polydactylous phenotype in mammals.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 19: HOXD13 mutations and synpolydactyly – digit number regulation.

View Details
Genetic Crosses

Polydactyly showing 65–90% expression is an example of

Polydactyly extra digits provides classic human example of incomplete penetrance with dominant allele showing 65-90% expression. In family surveys, 10-35% of individuals who inherit pathogenic variant remain phenotypically normal with five digits, despite carrying mutation. Developmental buffering, modifier loci, and limb patterning threshold variability explain non-penetrance. Consequently unaffected parents can transmit allele to affected children, mimicking recessive inheritance or new mutation. Penetrance value derived from population pedigrees aids counselors calculating recurrence risk and explaining why generation skipping does not rule out dominant transmission.

Ref: Hartl, Essential Genetics, Chapter 5: Incomplete Penetrance Example of Polydactyly

View Details