A poor but ambitious graduate student has discovered a goldfish with blue scales
ID: 54168 • Letter: A
Question
A poor but ambitious graduate student has discovered a goldfish with blue scales, a very unusual color in this species. Envisioning a lucrative possibility for the aquarium fish trade, she hoped to produce a pure-breeding blue-scaled goldfish. She crossed blue and normal individuals in every different combination, with the outcomes that appear below. In no case was she able to produce the pure-breeding blue line she sought.
Cross type Combined results of large litters from multiple matings normal x normal (12 crosses): 497 normal : 0 blue
normal x blue (14 crosses): 248 normal : 236 blue (all litters contained some normal and some blue individuals)
blue x blue (13 crosses): 131 normal : 255 blue (all litters contained some normal and some blue individuals, but no litters were 100% blue)
Suggest a simple and reasonable genetic hypothesis to explain the inheritance of the blue-scale characteristic and briefly explain your answer.
Explanation / Answer
Extra genetical factors influence the trait that encodes color of scales. These factors called epigenetics. The color encoding trait overlap on normal genes and exhibit incomplete dominance.