A 3.5-kb segment of DNA containing the complete sequence of a mouse gene is available. The DNA segment contains the promoter sequence and extends beyond the polyadenylation site of the gene. The DNA is studied by band shift assay, and the following gel bands are observed.

Match these conditions to a specific lane of the gel.
3.5-kb fragment plus RNA polymerase II

Verified step by step guidance

1. Step 1: Understand the experimental setup. A band shift assay is used to study protein-DNA interactions. When RNA polymerase II binds to the DNA fragment, it alters the mobility of the DNA in the gel, causing a shift in the band position.
2. Step 2: Analyze the gel image provided. The gel contains five lanes, each showing bands corresponding to different experimental conditions. The lanes are numbered 1 through 5.
3. Step 3: Match the condition '3.5-kb fragment plus RNA polymerase II' to the appropriate lane. Look for a lane where the band is shifted compared to the control lane (which contains only the 3.5-kb DNA fragment without RNA polymerase II). This shift indicates the binding of RNA polymerase II to the DNA.
4. Step 4: Identify the control lane. Typically, the control lane will show the unaltered position of the 3.5-kb DNA fragment. Compare the band positions in the other lanes to this control to determine which lane shows the interaction with RNA polymerase II.
5. Step 5: Confirm the lane where the band is shifted upward or has altered mobility, as this indicates the presence of RNA polymerase II bound to the DNA fragment. This lane corresponds to the condition described in the problem.

Key Concepts

Promoter Sequence

The promoter sequence is a region of DNA located upstream of a gene that initiates transcription. It serves as the binding site for RNA polymerase and transcription factors, facilitating the assembly of the transcription machinery. Understanding the promoter's role is crucial for analyzing gene expression and the effects of regulatory elements.

RNA Polymerase II

RNA polymerase II is an enzyme responsible for synthesizing messenger RNA (mRNA) from a DNA template during transcription. It plays a vital role in gene expression by transcribing protein-coding genes. The interaction between RNA polymerase II and the promoter is essential for initiating transcription, making it a key focus in studies of gene regulation.

Gel Electrophoresis

Gel electrophoresis is a laboratory technique used to separate DNA, RNA, or proteins based on their size and charge. In this method, samples are loaded into a gel matrix and subjected to an electric field, causing molecules to migrate. The resulting bands can be analyzed to determine the presence and size of specific fragments, which is critical for interpreting results in molecular biology experiments.