Final answer:
The Bar eye mutation in Drosophila is a result of duplication of a section on the X chromosome affecting eye shape. Sex linkage significantly affects the inheritance of the Bar eye phenotype due to its location on the X chromosome.
Step-by-step explanation:
The Drosophila Bar eye mutation is an example of chromosome duplication. In Drosophila, the gene determining eye color is found on the X chromosome, with red being the wild-type, dominant color. The Bar eye phenotype is a result of duplication of a section of the X chromosome.
Here, a part of the X chromosome, which includes the gene that affects eye shape and size, is duplicated, leading to a narrower eye shape which appears bar-shaped when viewed from the front, hence the name 'Bar' phenotype.
The presence of multiple copies of this gene leads to the altered shape of the eyes in Drosophila because of gene dosage effects.
Notably, because this gene is located on the X chromosome, sex linkage plays a significant role in the inheritance patterns seen with Bar eye mutations. Females (XX) can be homozygous or heterozygous for the Bar mutation, while males (XY) can only carry one copy, given they have just one X chromosome.