are two epigenetic mechanisms that can prevent DNA from being accessible to transcription molecules. When the DNA is unwound, molecules that bind to determine when and how to transcribe genes. When gene transcription begins, a special type of protein known as binds to a promoter and assembles RNA. An activator is a transcription factor that binds to and promotes transcription. A repressor is a transcription factor that binds to and prevents transcription. Even if a gene is transcribed, its ultimate translation and expression can be silenced by

Alichen is an organism that structurally appears to be a single organism. but a lichen is actually two different organisms—a fungus and green algae—living together as one organism. the fungal partner derives its nutrition from the photosynthesizing algae. how does a lichen differ in its photosynthetic activity from elysia chlorotica, the sea slug that’s considered to be a photosynthesizing animal? a. in lichens, the fungi photosynthesize on their own, while elysia chlorotica forms a relationship with a photosynthesizing plant. b. in lichens, the relationship with the algae lasts throughout the life cycle, but in elysia chlorotica, the relationship occurs only during the immature juvenile stage of the slug’s life cycle. c. lichens can photosynthesize only because of the living algal partner, while elysia chlorotica incorporates chloroplasts from algae into its cells. d. in lichens, the association between the fungi and algae is permanent, while elysia chlorotica associates with a photosynthesizing organism only when it requires food.

Yeast cells reproduce quickly by budding. this is a form of reproduction so all the yeast cells a) sexual; vary b) asexual; vary c) asexual; are identical d) sexual; differ from the parents submit hint structures and functions of cells cellular reproduction

Describe the relationship between isotonic solutions, equilibrium, and water movement into and out of a cell.