DNA Structure and Function

Double Helix Structure

• DNA is structured like a twisted ladder, forming a shape known as a double helix.
• Sides of the Ladder:
  • Made of long chains consisting of alternating sugar (deoxyribose) and phosphate.
• Rungs of the Ladder:
  • Made of nitrogenous bases.

Nitrogenous Bases

• Four bases: labeled as A, T, C, and G.
• Full Names for Bases:
  • A for Adenine
  • T for Thymine
  • C for Cytosine
  • G for Guanine

Base Pairing Rules

• Adenine (A) always pairs with Thymine (T).
• Cytosine (C) always pairs with Guanine (G).

Nucleotide

• The combination of a phosphate, deoxyribose sugar, and nitrogenous base is known as a nucleotide.
• Nucleotides are the building blocks of DNA.

Genetic Code and Proteins

• Bases form a genetic code that provides instructions for the order of amino acids.
• Gene:
  • A section of DNA that codes for a specific protein.

Higher Tier: Triplet Code (WJEC Exam)

• Triplet Code:
  • Three bases are needed to code for one specific amino acid.
• Protein Synthesis:
  • In the cytoplasm, proteins are made by reading the code in groups of three bases.
  • Each triplet (group of three bases) matches a specific amino acid.
  • As the gene is read, a chain of amino acids is formed, which will fold into a specific protein.
  • Key Point: A gene codes for a specific protein.

Note

• This is a simplified explanation suitable for the WJEC exam.