DNA Structure and Protein Synthesis

This lesson covers the structure of DNA, the concept of a gene and genome, and the process of protein synthesis (transcription and translation). This is essential content for Edexcel GCSE Biology (1BI0) Topic 3: Genetics.

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DNA Structure

DNA stands for deoxyribonucleic acid. It is the molecule that carries the genetic information in all living organisms.

Key Features of DNA

• DNA is found in the nucleus of cells, organised into structures called chromosomes.
• DNA has the shape of a double helix — two strands twisted around each other, like a twisted ladder.
• Each strand is made up of a long chain of nucleotides.

Nucleotides

Each nucleotide consists of three parts:

1. A deoxyribose sugar (a five-carbon sugar).
2. A phosphate group.
3. A nitrogenous base (one of four types).

The sugar and phosphate groups form the backbone of each DNA strand (the sides of the "ladder"). The bases extend inwards and pair with bases on the opposite strand (the "rungs" of the ladder).

The Four Bases

There are four bases in DNA: