Gene regulation occurs at
I. translational level.
II. Transcriptional level.
III. Post transciptional level.
IV. Post translation level.
Choose the correct combination.

Options

A. I and II
B. III and IV
C. I and IV
D. I, II, III and IV

Answer

To solve the question regarding gene regulation, we need to analyze each option provided and determine whether gene regulation occurs at each specified level.

### Step-by-Step Solution:

1. **Translational Level (I)**:
- Gene regulation can occur at the translational level where the mRNA is translated into proteins. This involves mechanisms that can enhance or inhibit the translation of specific mRNAs into proteins. Therefore, gene regulation does occur at this level.

2. **Transcriptional Level (II)**:
- At the transcriptional level, gene regulation is crucial as it involves the process of converting DNA into mRNA. Regulatory proteins can bind to DNA and influence the rate of transcription, thus controlling gene expression. Hence, gene regulation occurs at this level as well.

3. **Post-Transcriptional Level (III)**:
- Post-transcriptional regulation involves modifications to the mRNA after it has been transcribed. This includes processes such as splicing, where introns are removed and exons are joined together. This regulation is important for producing mature mRNA that can be translated into proteins. Thus, gene regulation is also present at this level.

4. **Post-Translational Level (IV)**:
- After translation, proteins can undergo various modifications (like phosphorylation, methylation, etc.) that can affect their activity or function. This is known as post-translational regulation. Therefore, gene regulation also occurs at this level.

### Conclusion:
Since gene regulation occurs at all four levels mentioned (translational, transcriptional, post-transcriptional, and post-translational), the correct combination is **I, II, III, and IV**.

### Final Answer:
The correct combination is **1, 2, 3, 4**.

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