In mammals, the Sry gene on the Y chromosome is instrumental in the male sex determination process. However, in Drosophila, the Y chromosome is not associated with male sex determination, but it contains genes required for sperm development in the adult. The copy number of the X chromosome is linked to sex determination. Drosophila with two X chromosomes (e.g., XX) are female, and those with one X chromosome (e.g., XY) are male.
What would be the resultant phenotype of an XO Drosophila genotype?
The resultant phenotype of an XO Drosophila genotype would be a sterile male. This is because the X chromosome contains genes required for both female development and fertility in Drosophila. In the absence of a second X chromosome (as in the XO genotype), the individual would develop as a male but would be sterile due to the lack of necessary genes on the missing X chromosome for normal sperm development.
An XO genotype in Drosophila refers to an individual with only one X chromosome and no Y chromosome. In this case, the resultant phenotype would be male. This is because in Drosophila, sex determination is based on the number of X chromosomes, with a single X chromosome (XO) resulting in a male phenotype.
To determine the resultant phenotype of an XO Drosophila genotype, we need to understand the sex determination mechanism in Drosophila.
In Drosophila, the sex determination is based on the ratio of X chromosomes to the number of haploid sets of autosomes (also known as the X:A ratio). The presence of at least one X chromosome is necessary for female development, but the ratio of X chromosomes to autosomes ultimately determines whether an individual develops as a male or a female.
In wild-type Drosophila, females have two X chromosomes (XX), while males have one X chromosome (XY). However, there are exceptions to this rule. An XO genotype represents a single X chromosome without a corresponding second X chromosome. This condition typically occurs due to abnormal chromosomal segregation during oogenesis, resulting in the loss of one X chromosome.
In Drosophila, an XO genotype would most likely develop as a male. This is because the presence of a single X chromosome with a haploid set of autosomes corresponds to a 1:1 ratio, which is the normal sex determination ratio for males. While the XO genotype lacks the typical complement of two X chromosomes found in wild-type females, it still has the necessary X:A ratio for male development.
Therefore, the resultant phenotype of an XO Drosophila genotype would be a male.