Yeast are eukaryotic microorganisms that can use different sugars as a source of energy.

You have identified a yeast gene, sweetie, whose expression is activated when yeast cells are in the presence of sucrose.

To further study the regulation of sweetie you have isolated a loss$-$of$-$function mutation "mutant A$"-$ in which sweetie expression is on all the time $-$ that is$,$ transcription of sweetie is no longer sensitive to the presence$/$absence of sucrose and is ALWAYS ON$.$

Also, note that yeast are usually haploid $-$ they only have one copy of each chromosome and each gene.

Mutant A has a single base mutation in the DNA $800$ bp upstream of the sweetie gene

There is no open reading frame in this region.

Explain how this mutation is most likely causing the mutant A phenotype.

mutation A abolishes the binding site of an activator protein

mutation A abolishes the binding site of a repressor protein

mutation $A$ is in a gene that encodes an activator protein that regulates sweetie

mutation $A$ is in a gene that encodes a repressor protein that regulates sweetie

Not enough information has been given