Gene expression

Definition

Gene expression is the process by which the information encoded in a gene is used to synthesize a functional gene product, typically a protein. This process involves two main stages: transcription, where the DNA sequence of a gene is copied into messenger RNA (mRNA), and translation, where the mRNA is used as a template to build a protein. Understanding gene expression is crucial for grasping how genetic information is translated into the phenotypic traits of organisms, and it connects to the genetic code, genome organization, and cellular functions.

5 Must Know Facts For Your Next Test

1. Gene expression can be regulated at multiple levels, including transcriptional, post-transcriptional, translational, and post-translational modifications.
2. Eukaryotic gene expression is often more complex than prokaryotic due to additional layers of regulation, such as RNA splicing and modifications to chromatin structure.
3. In eukaryotes, mRNA must be processed before it can be translated; this includes capping, polyadenylation, and splicing out introns.
4. The genetic code consists of codons that specify which amino acids are added during protein synthesis, directly linking gene expression to protein function.
5. Environmental factors can influence gene expression, allowing organisms to adapt to changing conditions through mechanisms such as epigenetic changes.

Review Questions

• How does the process of transcription differ between prokaryotes and eukaryotes in relation to gene expression?
  • In prokaryotes, transcription occurs in the cytoplasm and is often coupled with translation due to the lack of a nucleus. The mRNA produced is typically polycistronic, meaning it can encode multiple proteins. In contrast, eukaryotic transcription takes place in the nucleus, producing monocistronic mRNA that encodes a single protein. Eukaryotic mRNA undergoes extensive processing, including splicing and modification before it is transported to the cytoplasm for translation.
• Discuss the role of transcription factors in regulating gene expression and how they interact with promoter regions.
  • Transcription factors are proteins that bind to specific DNA sequences near promoters to regulate the transcription of genes. They can act as activators or repressors; activators enhance transcription by recruiting RNA polymerase or facilitating its binding to the promoter, while repressors inhibit transcription by blocking access to the promoter or modifying chromatin structure. This interaction allows cells to finely tune gene expression in response to developmental cues or environmental changes.
• Evaluate the significance of epigenetic modifications in influencing gene expression patterns and their implications for cellular function and development.
  • Epigenetic modifications such as DNA methylation and histone modification play critical roles in determining gene expression patterns without altering the underlying DNA sequence. These changes can lead to long-term alterations in gene activity that affect cellular functions and contribute to processes like differentiation and development. For instance, epigenetic regulation can silence genes that should not be expressed in certain cell types, helping maintain cellular identity. Dysregulation of these modifications can lead to diseases like cancer, highlighting their importance in health and disease.

Related terms

Transcription: The first step of gene expression where the DNA sequence of a gene is transcribed into mRNA.

Translation:

The process in which ribosomes synthesize proteins using the mRNA sequence as a template.

Promoter:

A region of DNA that initiates transcription of a particular gene, serving as a binding site for RNA polymerase.