The genome and genesSpec 3.5
In short
The genome is the entire DNA of an organism, including all of its genes. A gene is a short section of a DNA molecule that codes for a specific protein. Each gene has a different sequence of bases, so each one codes for a different protein. The genome is all of the DNA, not just the genes.
- Genome
- The entire DNA of an organism.
- Gene
- A section of a DNA molecule that codes for a specific protein.
The genome includes all of the genes of an organism. A gene is a short section of the DNA. Each gene has a different sequence of bases and so codes for a different protein.
Exam tip:Use the exact wording. A gene codes for a specific protein, and the genome is the entire DNA, not just the genes.
Written and checked against the Edexcel GCSE Combined Science (1SC0) specification · Updated October 2026
Frequently asked questions
What is the structure of DNA?
DNA is a polymer made of nucleotides, with two strands coiled to form a double helix. Each nucleotide has a sugar, a phosphate group and one of four bases. The strands are linked by complementary base pairs, adenine with thymine and cytosine with guanine, held together by weak hydrogen bonds.
What is the difference between a gene and a genome?
A gene is a short section of DNA that codes for a specific protein, while the genome is the entire DNA of an organism. The genome includes all of the organism's genes. Each gene has a different sequence of bases, so each one codes for a different protein.
Why is salt added when extracting DNA from fruit?
Salt is added when extracting DNA from fruit because it helps the DNA clump together. Detergent is added with it to break down the cell membranes and nuclear membranes, so the DNA is released. After filtering, ice-cold ethanol is added, and the DNA comes out of solution as white, stringy strands.
All 4 questions on DNA and the genome
