Final answer:
A fruit fly with two sets of autosomes and 1 X chromosome without a Y chromosome is phenotypically female, as in Drosophila, an XX genotype determines females and an XY genotype determines males.
Step-by-step explanation:
If a fruit fly has two sets of autosomes, 1 X chromosome, and no Y chromosome, the sexual phenotype of this fly would be female, based on the genetic conventions found in Drosophila melanogaster. In Drosophila, the presence of two X chromosomes (XX) determines a female, while one X and one Y chromosome (XY) determine a male. Males are hemizygous having only one allele for any X-linked characteristic because they possess a single X chromosome and a Y chromosome, which lacks a second allele. Females, on the other hand, can be homozygous or heterozygous with their two copies of the X chromosome.
Since the fruit fly in question has only one X chromosome and lacks a Y chromosome, it defies the typical XY system of sex determination. However, in fruit flies, the absence of a Y chromosome doesn't result in male characteristics; it is the ratio of X chromosomes to sets of autosomes that matters. Typically an XY genotype determines males and an XX genotype determines females. Therefore, the correct answer is that the fruit fly with one X chromosome and no Y chromosome would be female.