DNA

DNA Structure

  • DNA (Deoxyribonucleic Acid) is a complex molecule that contains the instructions an organism needs to develop, live and reproduce.
  • It is made up of two strands coiled around each other to form a structure known as a double helix.
  • Each strand is made of chemical building blocks called nucleotides, which consist of a phosphate group, a sugar molecule (deoxyribose) and one of four types of nitrogen bases: Adenine (A), Thymine (T), Guanine (G), and Cytosine (C).

DNA Base Pairing

  • DNA structure features a specific pattern: Adenine always pairs with Thymine, and Guanine always pairs with Cytosine. These pairs make up the “rungs” of the DNA double helix.
  • The correct base pairing is essential for DNA to function correctly and is ensured by the ability of each base to form hydrogen bonds with its partner.

DNA Replication

  • The process whereby DNA makes a copy of itself is known as DNA replication.
  • This happens during cell division, ensuring that each new cell has the full complement of DNA molecules.
  • During DNA replication, the double helix unwinds and enzymes break the hydrogen bonds between the base pairs.
  • Each strand then serves as a template for a new DNA molecule to be formed.

Role of DNA

  • The DNA sequence, or order of bases, forms the instructions to make proteins.
  • These instructions are carried from the DNA in the nucleus to the ribosomes in the cytoplasm by an intermediary molecule called mRNA (messenger RNA) in a process called transcription.
  • The sequence of bases in the DNA determines the order of amino acids in a protein. This process, known as translation, decides the protein’s shape and function.
  • Since proteins are responsible for a large number of roles within a cell, from catalysing reactions to transporting molecules, the genetic code carried in DNA is crucial for the proper functioning of an organism.

DNA Mutations

  • A mutation is a change in the sequence of DNA bases, and it can occur when DNA replicates.
  • These alterations can have a variety of effects on the produced proteins, changing an organism’s traits.
  • Mutations can be beneficial, harmful, or neutral, and they contribute to the genetic diversity within a species.