Question

Brachydactyly type D (Clubbed Thumb)

Assignment: Inheritance

Background: The images above shows an individual with a common thumb variant (recessive trait) and one with brachydactyly type D (dominant trait). The reduced length and increased girth of the distal phalanx in brachydactyly type D has to do with a mutation on HOXD13 (part of the hoxD gene cluster on Chromosome 2) that effects its pattern of development.

Your question: Considering that brachydactyly type D is controlled by a dominant allele, will it replace the common recessive thumb allele over time? As part of your answer you must make use of Mendel's laws of inheritance.

1. Make sure you explain why you think the dominant allele will or will not replace the recessive allele. You will have to look over Mendel's laws of inheritance to answer this question correctly.

2. Student will cite their work.

Answer 1

Stub thumbs are medically Classified as brachydactly type (BDD) or BDD is exhibits autosomal dominance This condition associated with the HoXD gene which is central in digital formation and growth. (cells carry 2 copies of each chromosome) In different version gene are called allels. Allels (depends on associated traits) If the both alleles are dominant it is called co dominance rightarrow both alleles being expressed equally. Ho times D - 13 - protein Hox - D13 is a protein in human is encoded by HOxD13. gene.