Final answer:
Genes are integral to cellular function and are responsible for coding proteins and RNA molecules. The gene expression can be regulated, meaning genes can be turned on or off to meet the cell's needs. The gene theory underscores the role of genes in defining an organism's characteristics.
Step-by-step explanation:
Understanding Genes and Gene Expression
The statement 'Genes are the keys to almost everything that living cells do' highlights the fundamental role of genes in the biological functions of cells. Genes found within the genome of a cell code for proteins and RNA molecules, each playing a specific role. However, not all genes are constantly active; cells can turn genes on or off, which is known as gene expression. This regulation allows cells to adapt to environmental conditions and perform their specialized functions effectively.
While the genotype, or genetic makeup, of a cell remains constant throughout its life, the expression of the genes can vary significantly. This dynamic process ensures efficiency and conservation of energy, which is particularly important for organisms like bacteria. Moreover, the universality of the genetic code allows genes to be inserted from one organism into another distant organism, such as inserting human genes into bacteria, and still be able to produce the correct protein. This is a testament to the shared biochemical pathways and genetic mechanisms across different forms of life.
The gene theory further explains that living organisms' characteristics are defined by their genes, which are distributed across chromosomes within each cell. While all cells carry the same DNA blueprint, each cell type may express a different subset of these genes depending on their specific role and environmental context.