What is Nucleic Acid?

Meaning and Definition of Nucleic Acid

Every living organism must carry with it instructions to build a new version of itself and make products to keep it alive. These instructions are in the nucleic acid.

All organisms with more than one cell use a nucleic acid called deoxyribonucleic acid (DNA), and less complicated ones, like viruses, use ribonucleic acid (RNA).

Each of these nucleic acids is a chain of many individual molecules, and when the life form reads these molecules in sequence, it identifies which product to make.

Of the two nucleic acids, RNA is the less complicated. It exists as a single thread. DNA, on the other hand, pairs up with another strand of DNA, so it is present in cells as a spiral-shaped, double-stranded structure.

Each nucleic acid is a chain, which is made up of many building blocks, one after another, called nucleotides. These nucleotides are joined by chemical forces at each end of the block.

Only four different nucleotides make up DNA. These are adenine (A), guanine (G), thymine (T), and cytosine (C.) RNA also has only four nucleotide blocks, but instead of thymine (T), it has uracil (U.)

A living being contains many nucleic acid instructions in its cells. Each cell can read the string of instructions and make the relevant outputs. Because each organism needs to make many different products, the nucleic acid chain contains many small sections of instructions. These sections are called genes, and the cell generally reads each gene as the instructions for a particular product.

It’s the nucleotide sequence that matters with nucleic acids, and complicated instructions don’t need more than four nucleotides. The human genome, for example, contains 3.2 billion nucleotides in each chain. Smaller organisms tend to have shorter nucleic acids, such as the bacterium Haemophilus influenzae at 1.8 million bases per chain.

An analogy is the fact that the English language has 26 letters, but English speakers can put all these letters together, in different word combinations, and have complex conversations.

A very simple example is when someone says “pots”. The same letters in reverse mean something completely different; “Having.” So, in another example, when the cell reads a gene with a sequence starting CCTTGGAA…, it will make a different cellular product than the one starting AATTGGAA… even though the sequences are similar.

Nucleic acid sequences in genes must be relatively precise, otherwise the organism may not be able to build the correct product.

Basically, nucleic acids function as the computer that organizes the cell. They also provide the instructions that the cell needs to replicate. Without nucleic acid, a cell or organism cannot build another version of itself. Only life forms that can replicate can survive into the next generation.

That is why nucleic acids are present in all forms of life on earth.

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