Final answer:
True, cells can change gene expression in response to external signals through the regulation of transcription. This allows cells to adapt to environmental changes and undergo processes like differentiation. These responses are triggered by molecules like hormones and nutrients that bind to cell receptors, leading to cellular changes.
Step-by-step explanation:
The statement is True: a cell can indeed change the expression of its genes in response to external signals. Even though the genotype of a cell remains constant, the gene expression is dynamic and can be altered by the environment. Cells can regulate the levels of enzymes and other proteins by turning genes on or off, primarily through the regulation of transcription in response to extracellular environmental signaling. This process starts with various chemicals such as hormones, nutrients, or toxins that can diffuse through the air, water, or, in multicellular organisms, circulate within body fluids like blood or lymph.
For example, cells have protein receptors on their surfaces that trigger internal signaling pathways when a specific molecule binds to them. These signals can then reach the nucleus and influence whether specific sections of DNA are transcribed, thereby turning on or off the production of certain proteins. This modulation of gene expression is essential for processes like cell differentiation, response to environmental stresses, and developmental changes.
Gene expression is a complex process that can be influenced at various stages, such as transcriptional control, post-transcriptional modifications, translational control, and post-translational modifications, illustrating the dynamic nature of cellular response to external and internal cues. This biological mechanism allows for the diversity of cell functions and specialization despite sharing the same DNA across different cell types.
Examples of Gene Regulation
- Gene-regulatory elements in DNA and transcription factors respond to developmental cues.
- Hormones released by endocrine glands can act as signal molecules that affect gene expression in target cells.
- Stimulation of protein receptors on the cell surface initiates signaling pathways that influence gene transcription.