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The ratio of total protein content to total RNA content was measured in yeast cells during log phase growth under two conditions:

1. Minimal media
2. Minimal media supplemented with an amino acid cocktail

In the amino acid-supplemented condition, the protein-to-RNA ratio increased dramatically.

Correct option is C

The experiment compared the ratio of total protein content to total RNA content in yeast cells grown in minimal media and amino acid-supplemented media. The key observation is that protein-to-RNA ratio increased dramatically in amino acid-supplemented conditions.

To understand this, let's analyze the biological implications:

1. The protein-to-RNA ratio represent :

   • RNA (mainly rRNA) is a key component of ribosomes, which are necessary for protein synthesis.
   • Protein synthesis depends on the availability of amino acids. If amino acids are limited, translation slows down even if mRNA and ribosomes are present.
   • A higher protein-to-RNA ratio suggests that protein synthesis (translation) is more efficient relative to transcription.

2. What happens in minimal media:

   • Minimal media lacks many essential amino acids, forcing yeast cells to synthesize them.
   • When amino acids are scarce, protein translation is strongly reduced, but RNA synthesis (transcription) is less affected.
   • This means that in minimal media, ribosomes and RNA might still be produced, but the actual translation of proteins is restricted due to amino acid limitation.

3. When amino acids are supplemented:

   • Amino acid supplementation removes the bottleneck in protein synthesis, allowing ribosomes to efficiently translate mRNA.
   • This increases protein production, raising the protein-to-RNA ratio.

Option 3 is Correct:

• The observation that protein-to-RNA ratio increases with amino acid supplementation suggests that protein translation is more limited than transcription in minimal media.
• This is because transcription of ribosomal RNA and mRNA can still occur in minimal media, but translation is inefficient due to the lack of amino acids.

Option 1: "In minimal medium, proteins are degraded at a higher rate."  (Incorrect)

• The data only indicates a change in the protein-to-RNA ratio, which suggests changes in protein synthesis, not degradation.
• Increased protein degradation would not necessarily explain the large increase in protein-to-RNA ratio in supplemented media.

Option 2: "In amino acid-supplemented culture conditions, fewer ribosomes are simultaneously active on a single transcript."  (Incorrect)

• Amino acid supplementation would actually increase ribosome activity, leading to more efficient translation.
• If fewer ribosomes were active per transcript, protein synthesis would be slower, which contradicts the observed increase in protein-to-RNA ratio.

Option 4: "Amino acid supplementation reduces RNA synthesis by modification of RNA Polymerase II." (Incorrect)

• There is no direct evidence that RNA Pol II is modified due to amino acid supplementation.
• Also, RNA Pol II is mainly involved in mRNA synthesis, whereas the RNA measured in the experiment likely includes rRNA (which forms ribosomes).
• Even if transcription slows, it wouldn’t necessarily increase the protein-to-RNA ratio unless translation is also significantly boosted.