Question

Match each term with its description. (a) Transcription ____________ (b) RNA polymerase _____________ (c) Sigma \((\sigma)\) factor____________ (d) Promoter________________ (e) Consensus sequence_______________ (f) Rho \((\rho)\)______________ (g) Operon________________ (h) Operator_________________ (i) Repressor_______________ (j) Inducer___________ 1\. Recognizes promoter sites 2\. The average order of nucleotides 3\. Repressor binding site 4\. RNA synthesis 5\. DNA sequences that determine the site of transcription initiation 6\. Consists of regulatory elements and proteinencoding genes 7\. In the lac operon, allolactose 8\. Prevents the transcription of structural genes 9\. RNA-synthesis-termination protein 10\. Transcriptional machinery

Short answer

(a) 4, (b) 10, (c) 1, (d) 5, (e) 2, (f) 9, (g) 6, (h) 3, (i) 8, (j) 7

Step-by-step solution

Match Transcription

Transcription is the process of synthesizing RNA from a DNA template, which corresponds to the description: 4. RNA synthesis.

Match RNA Polymerase

RNA polymerase is the enzyme responsible for synthesizing RNA, which matches the description: 10. Transcriptional machinery.

Match Sigma Factor

The sigma (σ) factor recognizes promoter sites and assists RNA polymerase in initiating transcription, matching description: 1. Recognizes promoter sites.

Match Promoter

A promoter is a DNA sequence that marks the site for transcription initiation, matching description: 5. DNA sequences that determine the site of transcription initiation.

Match Consensus Sequence

A consensus sequence represents the average sequence or the most common sequence found at a particular site, matching description: 2. The average order of nucleotides.

Match Rho Factor

Rho (ρ) is a protein involved in terminating RNA synthesis, fitting the description: 9. RNA-synthesis-termination protein.

Match Operon

An operon is a group of genes regulated together including regulatory sequences and structural genes, matching description: 6. Consists of regulatory elements and protein-encoding genes.

Match Operator

The operator is the DNA segment that repressor proteins bind to prevent transcription, fitting description: 3. Repressor binding site.

Match Repressor

A repressor is a protein that binds to the operator to inhibit gene transcription, matching description: 8. Prevents the transcription of structural genes.

Match Inducer

An inducer, like allolactose in the lac operon, is a molecule that starts gene expression by binding to a repressor, matching description: 7. In the lac operon, allolactose.

Key concepts

Transcription

Transcription is a fundamental biological process that occurs in all living organisms. It involves converting the information encoded in a DNA template into a corresponding RNA molecule.

• This process is vital because it serves as the first step in gene expression, allowing a cell to produce proteins and perform essential functions.
• During transcription, specific enzymes read the DNA sequence and create a complementary RNA molecule. This RNA then carries the genetic message from the DNA in the nucleus to the ribosome, where proteins are synthesized.

A critical part of the transcription process is the creation of messenger RNA (mRNA), which serves as a transient copy of the genetic code. Understanding transcription gives insight into how genes control cellular activities.

RNA Polymerase

RNA Polymerase is a key enzyme in the process of transcription. It plays a critical role by catalyzing the synthesis of RNA from the DNA template.

• RNA polymerase binds to specific regions of the DNA known as promoters, initiating the transcription of the DNA sequence into RNA.
• This enzyme adds ribonucleotides to the growing RNA chain, directed by complementary base pairing with the DNA template.

There are multiple types of RNA polymerase, each with specific functions, yet the core job remains to ensure the accurate and efficient production of RNA molecules necessary for gene expression.

Promoter

A promoter is a specific DNA sequence that acts as a signal for the transcription machinery to begin transcription. It is a crucial part of gene regulation.

• The promoter is located near the start of a gene, serving as a binding site for RNA polymerase and associated transcription factors.
• Promoters contain specific sequence motifs that are recognized by the transcriptional machinery, allowing for precise control over when and where transcription begins.

Understanding how promoters work helps comprehend how cells control gene expression in response to environmental changes. They play a pivotal role in determining the genes that are expressed, thus impacting cellular function.

Operon

The operon model provides a fundamental mechanism for gene regulation in prokaryotic cells, helping to coordinate the expression of multiple genes.

• An operon consists of a cluster of genes under the control of a single promoter. These genes are transcribed together as a single mRNA strand, allowing for coordinated expression based on environmental conditions.
• It usually includes regulatory sequences like operators, which can be bound by proteins (repressors or activators) to control transcription.

One classic example is the lac operon in E. coli, which regulates the metabolism of lactose. Understanding operons is critical in genetics, as they illustrate how organisms efficiently manage gene expression and adapt to their environment.