Problem 9 - Campbell Biology

Question

Within a cell, the amount of protein made using a given mRNA molecule depends partly on \begin{equation} \begin{array}{l}{\text { (A) the degree of DNA methylation. }} \\ {\text { (B) the rate at which the mRNA is degraded. }} \\ {\text { (C) the number of introns present in the mRNA. }} \\ {\text { (D) the types of ribosomes present in the cytoplasm. }}\end{array} \end{equation}

Step-by-Step Solution

Answer

B) the rate at which the mRNA is degraded.

Step 1: Understanding the Question

The question asks what factors influence the amount of protein made from an mRNA molecule within a cell.

Step 2: Identify the Possible Factors

Different factors are presented: A) Degree of DNA methylation, B) Rate of mRNA degradation, C) Number of introns in the mRNA, and D) Types of ribosomes in the cytoplasm.

Step 3: Assess DNA Methylation

DNA methylation affects gene expression but not directly the amount of protein from an existing mRNA. Thus, option A can be ruled out.

Step 4: Consider mRNA Degradation Rate

The rate at which the mRNA is degraded directly affects how long mRNA will be available for translation. Faster degradation means less protein can be made. Option B is a likely factor.

Step 5: Evaluate the Number of Introns

Introns are non-coding regions removed during mRNA processing, so their number in a mature mRNA should not directly influence protein production. This makes option C irrelevant.

Step 6: Evaluate Ribosome Types

The types of ribosomes present can influence the efficiency of translation, potentially affecting protein synthesis. However, it still doesn't directly tie to the amount of protein from a given mRNA. Option D is less likely.

Step 7: Determine the Correct Answer

Among the given options, the rate at which mRNA is degraded is the most direct factor influencing the amount of protein made. Therefore, the correct answer is B.

Key Concepts

mRNA degradation

The rate of mRNA degradation is a crucial factor in determining protein synthesis within a cell. mRNA molecules act as templates for protein synthesis, carrying genetic information from DNA to ribosomes. If an mRNA molecule degrades rapidly, it provides a shorter window for translation into proteins. This degradation process regulates gene expression by ensuring that mRNA levels are controlled and not lasting indefinitely. Degradation is often controlled by specific sequences and structures within the mRNA, along with associated proteins. This ensures precise regulation and adaptability in response to cellular conditions. In essence, mRNA degradation rates modulate how much protein is synthesized from a given mRNA template, impacting the overall protein expression.

gene expression

Gene expression involves converting genetic information from DNA into functional proteins. This process includes transcription (DNA to mRNA) and translation (mRNA to protein). Regulation occurs at multiple levels:

• Transcriptional control
• Post-transcriptional control
• Translational control
• Post-translational control

Factors like DNA methylation and histone modification can influence transcription, but they don't directly affect the amount of protein made from an existing mRNA. Instead, post-transcriptional mechanisms like mRNA splicing, export, localization, and degradation play pivotal roles. These intricate control mechanisms ensure that proteins are produced appropriately for the cell's needs.

translation efficiency

Translation efficiency refers to how effectively mRNA is translated into proteins. Several factors influence this:

• Ribosome availability and types
• mRNA sequence and structure
• Initiation factors and regulatory proteins

Efficient translation means more protein is produced in a given time, assisting in rapid cellular responses to changes. While factors like mRNA degradation and regulatory sequences directly control how long and how well an mRNA is translated, the overall translation machinery's efficiency also plays a significant role. This includes the ribosomes and other molecular players ensuring the mRNA is read correctly and swiftly, ultimately affecting protein synthesis.