The presence of a poly-A tail on a RNA molecule indicates that: A. there are exons present that must be removed B. this RNA molecule does not contain introns C. the transcript should be immediately degraded D. this is a rRNA molecule E. None of the above

E. None of the above

Explanation:

During transcription, a sequence called a polyadenylation signal occurs in an RNA molecule, an enzyme at that site chops the RNA in two. The enzyme adds to the cut end around 100-200 adenine (A) nucleotides which form a poly-A tail at 3' end. The tail make transcript which is more stable and functions to be exported to the cytosol from the nucleus. Some sections of the RNA transcript (introns) are deleted when splicing, and the remaining sections (exons) are kept together.

Hence, the corrcet option is E.

4.) metal

"-the movement of carbon from the nonliving environment into living things and back to the environment

-carbon is the essential component of proteins, fats, and carbohydrates (which make up all organisms)

-carbon exists in air, water, and living organisms

-producers convert carbon dioxide in the atmosphere into carbohydrates during photosynthesis

-bacteria in the atmosphere cycles through the system in filtration units

-in cellular respiration, carbon is released back into the atmosphere as carbon dioxide

-some carbon is stored in limestone (forming one of the largest "carbon sinks" on earth)

-largest carbon reservoir on earth= limestone

-carbon stored in the bodies of organisms as fat, oils, or other molecules may be released into the soil or air when the organism dies

-this may form deposits of coal, oil, or natural gas (fossil fuels, which increased the atmospheric carbon dioxide)

-fossil fuels store carbon left over from bodies of organisms that died millions of years ago

-they are located in the surface of earth, deep within the earth and beneath the ocean floor."