c
A Sxl knockout would result in XX flies that have female organs and XY flies that have male organs
e
A Tra knockout would result in XX flies that have male organs and XY flies that have female organs
Sex determination in Drosophila is linked to the level of expression of the Sex-lethal gene (Sxl) on the X chromosome. Additional genes that determine sex are transformer (Tra) and doublesex (dsx).
In females with two X chromosomes, Sxl is expressed from an early promoter and act as a splicing factor for Sxl pre-mRNA and tra pre-mRNA. In both cases, exons that contain premature stop codons are spliced out and full length Sxl and Tra proteins are produced. The Sxl mRNA contains exons 1-2-4-5-6-7-8.
Tra protein acts as a splicing factor to make Dsx protein encoded by exons 1-2-3-4 of the dsx gene. This female Dsx protein activates female-specific genes and inhibits male-specific genes for sex determination.
In the male, the Sxl gene is driven by a late promoter, so exon 3 containing a premature stop codon is retained in the mRNA, and truncated, nonfunctional Sxl protein is made. A truncated Tra protein is made since exon 2 with a premature stop codon is not spliced out. A "male” Dsx protein is made from exons 1-2-3-5-6 of the dsx gene and activates male-specific genes for sex determination.
Which of the following statements is correct? Select ALL that apply.
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a
Injection of Sxl protein in an XY male during development would result in the production of female organs
b
Injection of "female" Dsx protein in an XY male during development would result in the production of female organs
c
A Sxl knockout would result in XX flies that have female organs and XY flies that have male organs
d
A Sxl knockout would result in XX flies that have male organs and XY flies that have female organs
e
A Tra knockout would result in XX flies that have male organs and XY flies that have female organs
1 answer