A student adds a suspension of baker's yeast cells into bread dough. When is this mixture is left in a large bowl undisturbed for several hours, the student returns to find that the bread dough has double in size. What gas molecules is responsible for this increase in dough size?

Pls me i need this ! each cell has genes activated depending on it's job and what kind of cell it is. it is the presence of that causes the repressor protein to fall off and unblock the gene on the lac operon. if a gene is turned on then it is being an additional circular chromosome found in some bacteria that is used in genetic engineering.