What are epigenetic modifications?
the addition of reversible changes to histone proteins and dna
the removal of nucleosomes from the dna
the addition of more nucleosomes to the dna
mutation of the dna sequence

This are epigenetic modification: a, b and c. (changes on histones, removal and nucleosomes formation.

Explanation:

Histone modification is a key step in genomic regulation. Activation of histones leads DNA to form new nucleosomes, which low transcription levels in this zone.  

On the other hand, deactivation of histones removes those nucleosomes, permitting DNA to be transcripted.

The addition of more nucleosomes to the DNA.

Explanation:

explanation:

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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."