Nucleic acids

• Nucleic acids are large, complex biomolecules essential for storing genetic information, synthesizing proteins, and regulating gene expression.

• They are composed of nucleotides, which consist of a pentose sugar, a phosphate group, and a nitrogenous base.

• These molecules primarily contain carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and phosphorus (P).

Classification of Nucleic Acids

Nucleic acids are classified into two main types, each with distinct structures and functions:

• Nucleic acids are classified into two major types, each with distinct structures and functions:

1) Deoxyribonucleic Acid (DNA)

• Structure

  • DNA is a double-stranded molecule with two complementary chains forming a double helix.

  • Composed of deoxyribose sugar and four nitrogenous bases:

  • Adenine (A), Thymine (T), Cytosine (C), Guanine (G).

• Function

  • Stores genetic information for protein synthesis, cellular functions, and inheritance.

• Examples

  • Found in the nucleus, mitochondria, and chloroplasts of cells.

2) Ribonucleic Acid (RNA)

• Structure

  • RNA is typically single-stranded and exists in multiple forms.

  • Contains ribose sugar and four nitrogenous bases:

  • Adenine (A), Uracil (U), Cytosine (C), Guanine (G) (Uracil replaces Thymine in RNA).

• Function

  • Plays a critical role in protein synthesis and gene regulation.

• Types of RNA and Their Roles

  • mRNA (Messenger RNA): Transcribes genetic information from DNA and transports it to ribosomes.

  • tRNA (Transfer RNA): Brings specific amino acids to the ribosome during protein synthesis.

  • rRNA (Ribosomal RNA): Forms the structural and functional core of ribosomes, catalyzing protein synthesis.

Table displaying the differences between the classifications of nucleic acids

Classification	Structure	Sugar	Bases	Function	Examples
DNA	Double-stranded, double helix	Deoxyribose	A, T, C, G	Genetic information storage, heredity, guiding protein synthesis	Genomic DNA, mitochondrial DNA
RNA	Usually single-stranded, various structures	Ribose	A, U, C, G	Protein synthesis, gene regulation, catalytic activities, genetic information transfer	mRNA, tRNA, rRNA, miRNA, lncRNA

Properties of Nucleic Acids

Polarity

• Nucleic acids have a directional structure with a 5' phosphate group at one end and a 3' hydroxyl group at the other, determining how nucleotides are added during synthesis.

Base Pairing

DNA bases form specific hydrogen bonds:

• A pairs with T (in DNA) or U (in RNA).

• C pairs with G in both DNA and RNA.

• This complementary pairing ensures accurate replication and transcription.

Stability

• DNA’s double-stranded structure and deoxyribose sugar make it more chemically stable than RNA, which is more prone to degradation due to its single-stranded nature.

Functions of Nucleic Acids

Genetic Information Storage

• DNA stores hereditary information essential for development, function, and reproduction.

Protein Synthesis

• mRNA carries genetic instructions from DNA to ribosomes.

• tRNA delivers amino acids for protein assembly.

• rRNA facilitates the formation of proteins.

Gene Regulation:

• Non-coding RNAs (e.g., microRNAs, long non-coding RNAs) regulate gene expression at transcriptional and translational levels.

Chemical Nature and Biological Role

Chemical Nature

• DNA and RNA consist of nucleotide chains, with structural differences:

• DNA: Contains deoxyribose sugar, uses Thymine (T) instead of Uracil (U).

• RNA: Contains ribose sugar, replaces Thymine with Uracil.

Biological Role

• Genetic Information Storage:

  • DNA encodes genetic instructions for protein synthesis and cellular function.

• Transcription and Translation:

  • DNA is transcribed into RNA, which is translated into proteins—the functional molecules of the cell.

• Gene Regulation:

  • RNA molecules help control gene expression, determining which proteins are produced and when.