Why does DNA need to be opened before mRNA
can be built?

Explanation:

DNA (Deoxyribonucleic acid )

DNA is a molecule made up of two polynucleotide chains that coil around each other to form a double helix and carry genetic instructions for the development, function, growth, and reproduction of all known organisms and viruses. DNA and ribonucleic acid are examples of nucleic acids (RNA).

Since they are made up of smaller monomeric units called nucleotides, the two DNA strands are known as polynucleotides. Each nucleotide is made up of a sugar called deoxyribose, a phosphate group, and one of four nitrogen-containing nucleobases (cytosine [C], guanine [G], adenine [A], or thymine [T]).

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