Two ground hogs with bulging eyes were kept in captivity, and were mated over a

Question

Two ground hogs with bulging eyes were kept in captivity, and were mated over a six-year period. Ground hogs mate once a year after exiting from hibernation. The numbers and phenotypes of their offspring that were observed each mating season, and are listed below. No ground hogs were harmed in these experiments as all the progeny were given away to good homes. What type of inheritance pattern appears to be at play for these two traits? Explain

.

mating season number of each eye phenotype

1 1 bulging 1 normal

2 3 bulging 1 normal

3 4 bulging 2 normal

4 3 bulging 2 normal

5 3 bulging 1 normal

6 2 bulging 1 normal

Explanation / Answer

The inheritance pattern is autosomal dominant. It is very clear from the results. Please note that this fact can be cross- checked from literature review also.

Let the genotype of bulging eyes be 'B'; so, genotype for normal will be 'b'.

The genotype of the two ground hogs kept in captivity is Bb and Bb. This is because both had bulging eyes; and were giving normal offsprings every year. Normal offsprings every year means that these hogs are heterozygous.

Bb X Bb

Phenotypic result will be 3 bulging: 1 normal. That is seen in 2nd mating season. In the first mating season, only two offsprings are produced. Out of these, one is normal. In the 3rd mating season also, ratio is 2 (bulging):1 (normal). So, the number of bulging is higher than normal offsprings. This simply states that bulging characteristic is dominant.

Please note that total bulging offspring after 6 years are = 16; and total normal offspring after 6 years = 8

The overall ratio is 2:1. This means that homozygous dominant (BB) fetus dies. Bulging characteristic will always be heterozygous (Bb)

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