Question

A man has six fingers on each hand and six toes on each foot. His wife and their daughter have the normal number of digits. Remember that extra digits are a dominant trait. What fraction of this couple's children would be expected to have extra digits?

Short answer

The fraction of the couple's children expected to have extra digits is ½ or half.

The change of occurrence of this trait is 50% since the father only has the dominant trait, not the mother.

Step-by-step solution

Description of polydactyly

The presence of extra fingers in the human body is the condition of polydactyly. It is a hereditary condition that is transferred from the parents to the offspring. This condition mostly occurs in fingers such as the thumb finger, middle finger, and little finger.

Description of dominant traits 

The particular distinguishing character belonging to a person is known as a trait. The one copy of the gene present in the chromosome that expresses a particular character is termed as dominant traits.

The dominant traits are predominantly expressed in the individuals. Here in this condition, polydactyly is a dominant condition.

Prediction of a fraction to get the condition of polydactyly

The father has the condition of six fingers and six toes, and the mother is in normal condition. The polydactyly condition is a dominant trait in this given condition. The fraction of the couple children expected to have extra digits is ½.

There is a possibility of 50% to pass this deformity in children since the father possesses the dominant trait and the mother is in normal condition.

Hence, the fraction is ½ for this given condition of polydactyly.