Purebred dogs are susceptible to many genetic disorders Cock

Purebred dogs are susceptible to many genetic disorders. Cocker spaniels, in particular, are prone to a disorder called canine phosphofructokinase (PFK) deficiency, an autosomal recessive condition in which glucose is unable to be metabolized into available energy. Because the PFK enzyme is important for energy metabolism in red blood cells and skeletal muscle during exercise, a deficiency in the enzyme results in exercise intolerance and muscle disease.

Use the pedigree below, which shows the inheritance of PFK deficiency in cocker spaniels, to answer the questions.

You are now considering breeding a female from litter f with the male from litter h. What is the probability that their offspring will be affected with PFK deficiency?

Please list the steps to reach the correct answer!

Hazel Hank Howey Hailey\'s parents Hailey Henry\'s parents Henry Halle

Solution

Phosphofructokinase deficiency is an autosomal disease in which glucose is not metabolised to the available form of energy. As it is a recessive disease it is expressed only when both the recessive genes are present.

In the present condition Hailey and Howey must be the carriers of the disease as one of the offsprings is afffected with the disease. Therefore, the male from litter h can be either a carrier or unaffected with the recessive gene. The genotype of litter h can be Aa or AA. The genotype of female from litter f can be Aa or Aa as all of them are unaffected with the disease.

Now if a cross is made between two carriers then the probability of the offspring to get the disease is 1/9.

Therefore, the probability of offspring affected by disease is 1/9.