Part I: Genetic Material
Lesson 1: Introduction to Cells, DNA, and Genes

Different sets of genes are active in different cell types. Although your muscle cells and nerve cells contain the same DNA sequences, they activate different sets of genes to give them different functions. Each cell type runs different programs. Muscle cells activate the genes needed to make muscle fibers. Nerve cells activate the genes needed to make neurotransmitters and connections with other nerve cells.