Genetic Crossover in Drosophila: Understanding Phenotypic Classes
Part A
Which of the following phenotypic classes reflect offspring that were generated as a result of a crossover event?
Select all that apply:
- garnet eyes
- wild type
- miniature wings
- miniature wings, garnet eyes
Part B
If 800 offspring were produced from the cross, in what numbers would you expect the following phenotypes?
__wild type : __ miniature wings : __ garnet eyes : __ miniature wings, garnet eyes
Enter your answer as the number of flies of each phenotype separated by a colon (example: 100:300:100:300).
Answer:
The following phenotypic classes reflect offspring that were generated as a result of a crossover event: - miniature wings - garnet eyes
When the genes for miniature wings and garnet eyes are 8 map units apart on chromosome 1 in Drosophila, a crossover event can occur during meiosis. This results in offspring with combinations of traits that differ from their parents.
When miniature wings and garnet eyes link up with the 8 map units that are present between them, recombinant classes are generated. These offspring display the following phenotypes:
- miniature wings
- garnet eyes
Based on the genetic linkage of these traits, we can expect the following approximate numbers of each phenotype in 800 offspring:
- wild type: 32 flies
- miniature wings: 368 flies
- garnet eyes: 368 flies
- miniature wings, garnet eyes: 32 flies