Why is it important to keep things controlled or constant during an experiment

Cells destroy body cells infected by a virus or bacteria.

Pl which diagram illustrates prophase?

Cattle with brown fur and cattle with white fur will produce a reddish roan calf . when examined closely, the calf show about an even number of brown hairs and white hairs that give a reddish appearance when viewed from far away. the fact that both the brown fur allele and the white fur allele are expressed equally in the offspring is an example of