Gene expression

Definition

Gene expression is the process by which information from a gene is used to synthesize functional gene products, typically proteins, that perform specific functions in the cell. This process involves transcription, where DNA is copied into messenger RNA (mRNA), followed by translation, where mRNA is decoded to build proteins. The regulation of gene expression is crucial for cellular differentiation and adaptation to environmental changes.

5 Must Know Facts For Your Next Test

1. Gene expression can be influenced by various factors such as environmental signals, transcription factors, and epigenetic modifications.
2. Supercoiling of DNA affects gene expression by influencing the accessibility of the DNA for transcription; tightly supercoiled DNA can inhibit transcription, while relaxed forms can enhance it.
3. Different cells express different genes at different times, allowing for specialization and adaptation based on the cell's function and environmental conditions.
4. Mutations in regulatory regions can lead to abnormal gene expression, potentially resulting in diseases such as cancer.
5. Feedback mechanisms are often involved in gene regulation, where the products of gene expression can influence their own expression levels.

Review Questions

• How does supercoiling affect gene expression in prokaryotic and eukaryotic cells?
  • Supercoiling influences gene expression by altering the physical state of DNA. In prokaryotic cells, negative supercoiling facilitates the unwinding of DNA for transcription, making it easier for RNA polymerase to access the genetic information. In eukaryotic cells, the interplay between supercoiling and chromatin structure also plays a critical role; supercoiling can compact or relax chromatin, thereby either inhibiting or promoting access to genes for transcription.
• What role do regulatory sequences play in the control of gene expression, especially regarding topological features of DNA?
  • Regulatory sequences are essential for controlling gene expression as they bind specific transcription factors that initiate or repress transcription. Topological features like supercoiling impact these regulatory sequences by affecting how tightly or loosely the DNA is packaged. This means that changes in DNA topology can directly influence whether these regulatory elements are accessible for protein binding, thus determining the level of gene expression.
• Evaluate the impact of external factors on gene expression regulation and discuss their relevance in cellular responses to environmental changes.
  • External factors such as temperature, nutrients, and stress conditions can significantly impact gene expression regulation. These factors can trigger signaling pathways that alter transcription factor activity, leading to changes in how genes are expressed. For instance, under stress conditions like heat shock, specific genes are upregulated to help the cell cope with damage. Understanding this regulation is crucial for deciphering how cells adapt to their environment and respond to various stimuli, providing insights into cellular functions and potential therapeutic targets.

Related terms

Transcription: The first step of gene expression where a specific segment of DNA is copied into mRNA by the enzyme RNA polymerase.

Translation: The second step of gene expression that occurs in the ribosome, where the mRNA sequence is read to assemble amino acids into a polypeptide chain, forming proteins.

Regulatory sequences: DNA sequences that are involved in controlling the timing and level of gene expression, including promoters and enhancers.