Nucleic Acids

Nucleic acids are essential biomacromolecules that carry and transmit genetic information. They are the building blocks of life, responsible for controlling all cellular activities and passing hereditary traits from one generation to the next. The two main types of nucleic acids are Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA).

1.0Structure of Nucleic Acids

Based on structure, nitrogen bases are broadly of two types:

The Nitrogenous Bases

1. Pyrimidines - Consist of one pyrimidine ring. The skeleton of the ring is composed of two Nitrogen and four Carbon atoms. e.g. Cytosine, Thymine and Uracil
2. Purines - Consist of two rings, i.e. one pyrimidine ring (2N + 4C) and one imidazole ring (2N + 3C), e.g Adenine, Guanine.

The Pentose Sugar

The sugar component is a key difference between DNA and RNA.

The Phosphate Group

• Nitrogen base forms a bond with the first carbon of the pentose sugar to form a Nucleoside.
• Nitrogen of first place (N1) forms a bond with sugar in the case of pyrimidines, while in purines, nitrogen of ninth place (N9) forms a bond with sugar.
• Phosphate forms an ester bond (covalent bond) with the fifth Carbon of sugar to form a complete nucleotide.

2.0Types of Nucleic Acids

Deoxyribonucleic Acid (DNA) 

DNA is the primary carrier of genetic information in most living organisms. It's a double-helical structure proposed by Watson and Crick. The two strands run in opposite directions, making them antiparallel.

• The strands are held together by hydrogen bonds between specific base pairs: Adenine always pairs with Thymine (A-T) with two hydrogen bonds, and Guanine always pairs with Cytosine (G-C) with three hydrogen bonds. This is known as Chargaff's rule of base pairing.
• The double helix is stable and well-suited for its primary function: storing genetic information.

Functions of DNA:

• Heredity: Stores the blueprint for all proteins and RNA molecules within an organism.
• Replication: It can make copies of itself, ensuring genetic information is passed to daughter cells during cell division.
• Transcription: DNA serves as a template for RNA synthesis.

Ribonucleic Acid (RNA) 

RNA is primarily involved in protein synthesis. Unlike DNA, it is typically single-stranded. RNA molecules are synthesized from a DNA template.

Types of RNA and their functions:

• Messenger RNA (mRNA): Carries the genetic code from DNA in the nucleus to the ribosomes in the cytoplasm.
• Transfer RNA (tRNA): Brings the correct amino acids to the ribosome during protein synthesis.
• Ribosomal RNA (rRNA): A major component of ribosomes, the machinery responsible for protein synthesis.
• Small nuclear RNA (snRNA): Involved in the splicing of pre-mRNA.

Functions of RNA:

• Protein synthesis (Translation): Translates the genetic information from mRNA into a sequence of amino acids.
• Gene expression regulation: Some RNA molecules, such as microRNAs (miRNAs) and small interfering RNAs (siRNAs), regulate gene expression.
• Genetic material: In some viruses (e.g., retroviruses), RNA serves as the genetic material.

3.0Functions of Nucleic Acids

Nucleic acids perform several critical functions in cells:

1. Storage of Genetic Information: DNA carries hereditary instructions.
2. Protein Synthesis: RNA facilitates the translation of the genetic code into proteins.
3. Regulation of Cellular Activities: Some RNA molecules act as regulators (e.g., miRNA).
4. Transmission of Genetic Information: DNA is replicated during cell division.

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