In humans the ability to bend the thumb back beyond vertical is called “hitchhik
ID: 276166 • Letter: I
Question
In humans the ability to bend the thumb back beyond vertical is called “hitchhiker’s thumb” and is recessive to the inability to do so. Also the presence of attached earlobes is recessive to unattached earlobes. In the pedigree shown, the left half of the circle or square is filled if the person has the dominant non-hitchhiker’s thumb and empty if the hitchhiker’s thumb is present. The right half of the symbol is filled if the person has unattached earlobes and is empty if earlobes are attached. Use allelic symbols H and h for the thumb and E and e for earlobes, and identify the genotypes of each family member. You can write directly onto the diagram.*
Explanation / Answer
According to the information, an individual with genotype HH or Hh would have bending thumb whereas that having genotype gg will be unable. Similarly, an individual with genotype EE or Ee will have free earlobes whereas that having ee will have fused earlobes. Thus, the genotypes of the pedigree can be found as below:
Parent 1 (male): HhEe
Parent 2 (female): HhEe
Offspring 1: hhee
Offspring 2: hhEe or hh EE
Offspring 3: hhEe or hh EE
Offspring 4: HhEe or HhEE or HHEe or HHEE