Lesson 1: The Instruction Manual

Key Idea

Cells contain a biological instruction manual called DNA. Specific sections of this manual are known as genes.

Each gene provides the specific directions for building a particular protein. The cell reads the gene and follows the instructions to construct the protein molecule needed for a specific job.

Key Idea

Genes for a specific feature can come in different variations. These are called gene versions (or alleles).

Each version gives slightly different instructions. One version might say "build Protein A," while another says "build Protein B." This genetic variety is the root cause of diversity in living things.

Key Idea

Because different gene versions give different instructions, they result in the creation of different protein molecules.

For example, in spiders, one gene version instructs cells to build a protein that makes flexible silk, while another version builds a protein for stiff silk. Thus, the specific genes an organism has determine which proteins its body builds.