DNA and RNA

Nucleic Acids Overview

• Nucleic acids are vital macromolecules carrying the genetic blueprint for life and directing cellular functions.

• The two main types are DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid).

• DNA stores genetic information and is found in the nucleus (eukaryotes) or cytoplasm (prokaryotes).

• RNA helps in protein synthesis and carries genetic instructions from DNA.

DNA (Deoxyribonucleic Acid)

• Structure: DNA has a double-helix structure made of two strands. Each strand is made up of nucleotides: nitrogenous bases (A, T, G, C), a pentose sugar (deoxyribose), and a phosphate group.

• Function: DNA stores and transmits genetic information. It controls cellular activities by turning genes “on” or “off”.

• Base Pairing: In the double helix, A pairs with T and G pairs with C (complementary base pairs).

• Strand Orientation: The two strands run antiparallel (opposite directions), with one strand from 5’ to 3’ and the other from 3’ to 5’.

• Replication: During DNA replication, each strand serves as a template to make a new complementary strand.

RNA (Ribonucleic Acid)

• Structure: RNA is typically single-stranded and is made of ribonucleotides (ribose sugar, phosphate group, and nitrogenous bases: A, U, G, C).

• Function: RNA is primarily involved in protein synthesis. It carries the message from DNA to the ribosomes to guide protein assembly.

• Types of RNA:

• mRNA (Messenger RNA): Carries genetic instructions from DNA to the ribosome.

• rRNA (Ribosomal RNA): Makes up the structure of ribosomes and helps with mRNA alignment.

• tRNA (Transfer RNA): Brings amino acids to the ribosome to build proteins.

• miRNA (MicroRNA): Regulates gene expression by interfering with mRNA.

Nucleotide Structure

Each nucleotide consists of:

• Nitrogenous Base (A, T, G, C, or U)

• Pentose Sugar (Deoxyribose in DNA, Ribose in RNA)

• Phosphate Group

• The sugar is attached to the base at the 1’ carbon and to the phosphate at the 5’ carbon.

• Phosphodiester Bonds link nucleotides together in a polynucleotide chain

Central Dogma of Molecular Biology

• The Central Dogma explains how genetic information flows: DNA → RNA → Protein.

• Transcription: DNA is transcribed into mRNA.

• Translation: mRNA is translated into a protein at the ribosome.

DNA Double-Helix Structure

• The double helix consists of two antiparallel strands.

• The phosphate backbone is on the outside, and the nitrogenous bases (A, T, G, C) are on the inside, paired via hydrogen bonds (A-T, G-C).

• Base Pairing: A forms two hydrogen bonds with T, and G forms three hydrogen bonds with C

• This structure is essential for DNA replication and the accuracy of gene expression.

Impact of Mutations

• A mutation, like replacing cytosine (C) with adenine (A), would change the DNA sequence, potentially affecting the protein produced.