The Hawaiian bobtail squid (Euprymna scolopes) is able to glow from luminescent Vibrio fischeri bacteria held in its light organs. As it swims at night near the ocean surface, it adjusts the amount of light visible to predators below to match the light from the stars and moon. Predators have difficulty seeing the illuminated squid against the night sky.
The bacteria glow in response to a molecule that regulates expression of genes involved in light-producing chemical reactions. The regulator controls production of the genes' mRNA. Therefore, the light-producing genes are under
a. Transcriptional control.
b. Translational control.
c. Post-translational control.
d. Negative control.

Verified step by step guidance

1. Begin by understanding the process of gene expression, which involves transcription and translation. Transcription is the first step where DNA is converted into mRNA, and translation is the process where mRNA is used to synthesize proteins.
2. Consider the role of the regulator molecule mentioned in the problem. It controls the production of mRNA for the light-producing genes. This indicates that the regulation occurs at the transcriptional level, as transcription is the process of creating mRNA from DNA.
3. Transcriptional control refers to the regulation of gene expression at the stage of transcription, where the synthesis of mRNA is either promoted or inhibited.
4. Translational control would involve regulation at the stage where mRNA is translated into proteins, which is not the case here as the problem specifies control over mRNA production.
5. Post-translational control involves modifications to proteins after they have been synthesized, which is also not applicable here. Negative control generally refers to mechanisms that inhibit gene expression, but the problem specifies regulation of mRNA production, aligning with transcriptional control.

Key Concepts

Transcriptional Control

Transcriptional control refers to the regulation of gene expression at the transcription stage, where the DNA sequence of a gene is transcribed into mRNA. This control determines whether a gene is turned on or off, influencing the amount of mRNA produced. In the context of the squid, the light-producing genes are regulated at this stage, affecting the production of mRNA necessary for luminescence.

Quorum Sensing

Quorum sensing is a mechanism by which bacteria communicate and coordinate behavior based on their population density. Vibrio fischeri uses quorum sensing to regulate bioluminescence, producing light only when a certain concentration of signaling molecules is reached. This ensures that the bacteria glow collectively, aiding the squid in its camouflage against predators.

Symbiotic Relationship

A symbiotic relationship is a close and often long-term interaction between two different biological species. The Hawaiian bobtail squid and Vibrio fischeri bacteria have a mutualistic symbiosis, where the squid provides a habitat and nutrients for the bacteria, and in return, the bacteria produce light that helps the squid avoid predators. This relationship is crucial for the squid's survival in its natural habitat.