DNA Structure and the Genome Revision Notes | GCSE OCR Foundation Biology

What this lesson covers

Learn about the structure of DNA as a double helix polymer, how genes code for proteins, and understand what the genome is and its importance for medicine.

• Describe the structure of DNA as a double helix polymer made of two strands
• Define genome as the entire genetic material of an organism
• Explain how genes code for specific proteins through amino acid sequences
• Evaluate the importance of understanding the human genome for future medicine

Key ideas to keep in view

Use this lesson to stay inside B1.2 What happens in cells (and what do cells need)? while connecting the detail back to the wider B1: Cell level systems topic.

• B1: Cell level systems
• B1.2 What happens in cells (and what do cells need)?
• GCSE OCR Foundation Biology

Lesson notes preview

Read the core explanations from DNA Structure and the Genome before testing yourself from memory.

• Every cell in your body contains a complete instruction manual - your DNA. This chemical holds the code for everything from your eye colour to how your muscles work. But DNA isn't just floating around randomly in your cells.
• Think of your cell nucleus as a library. The DNA is organised into structures called chromosomes - like books on shelves. Each chromosome contains thousands of genes, which are like individual recipes in a cookbook.
• A polymer made up of two strands forming a double helix. DNA contains the genetic material in the nucleus of a cell.
• Picture DNA like a twisted ladder - this is the famous double helix shape. The two strands spiral around each other, held together by chemical bonds between complementary bases.
• Trap: Many students think DNA is a single strand. Actually, it's always two strands twisted together - that's what makes it stable enough to store information reliably.
• 3. From DNA to Proteins - The Gene Connection
• A small section of DNA on a chromosome. Each gene codes for a particular sequence of amino acids, to make a specific protein.
• Here's where it gets clever. Your DNA doesn't directly make proteins. Instead, each gene acts like a recipe that tells the cell which amino acids to join together, and in what order.
• Think of it like this: Gene → Amino acid sequence → Protein → Function in your body. For example, one gene might code for insulin (a protein that controls blood sugar), while another codes for haemoglobin (the protein that carries oxygen in your blood).
• A structure containing DNA that is found in the nucleus of a cell. Chromosomes contain many genes.

Continue through the topic

Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.