During your work as a laboratory assistant in the research facilities of Dr. O. Sophila, a world-famous geneticist, you come across an unusual bottle of fruit flies. All the flies in the bottle appear normal when they are in an incubator set at 22°C. When they are moved to a 30°C incubator, however, a few of the flies slowly become paralyzed; and after about 20 to 30 minutes, they are unable to move. Returning the flies to 22°C restores their ability to move after about 30 to 45 minutes.

With Dr. Sophila's encouragement, you set up 10 individual crosses between single male and female flies that exhibit the unusual behavior. Among 812 progeny, 598 exhibit the unusual behavior and 214 do not. When you leave one of the test bottles in the 30°C incubator too long, you discover that more than 2 hours at high temperature kills the paralyzed flies. When you tell this to Dr. Sophila, he says, 'Aha! I know how to explain this condition.' What is his explanation?

Key Concepts

Temperature Sensitivity in Genetics

Temperature sensitivity refers to how certain genetic traits can be influenced by environmental temperatures. In this case, the fruit flies exhibit normal behavior at 22°C but show paralysis at 30°C, indicating that the expression of the trait is temperature-dependent. This phenomenon is often seen in organisms with temperature-sensitive alleles, where the protein function is altered at different temperatures.

Genetic Inheritance Patterns

The observed ratio of progeny exhibiting the unusual behavior suggests a genetic basis for the trait, likely following Mendelian inheritance patterns. The ratio of 598 to 214 indicates a potential dominant-recessive relationship, where the unusual behavior may be linked to a dominant allele. Understanding these patterns is crucial for predicting how traits are passed on through generations.

Phenotypic Plasticity

Phenotypic plasticity is the ability of an organism to change its phenotype in response to environmental conditions. In this scenario, the fruit flies demonstrate plasticity by exhibiting paralysis at higher temperatures, which may be a stress response. This concept is important for understanding how organisms adapt to varying environments and the potential evolutionary implications of such traits.