39. Eukaryotic RNA Polymerase II transcribes:
A. rRNA and tRNA genes
B. mRNA and tRNA genes
C. mRNA and 5S rRNA genes
D. mRNA, miRNA and snRNA genes

Detailed Explanation:

Eukaryotic RNA Polymerase II (Pol II) is a crucial enzyme in the process of transcription, which is the first step in gene expression. It is responsible for synthesizing messenger RNA (mRNA) and several other types of RNA that play critical roles in gene regulation and processing. Understanding the specific genes transcribed by RNA Polymerase II is key to appreciating its role in the eukaryotic cell.

What Does RNA Polymerase II Transcribe?

RNA Polymerase II transcribes a variety of genes that are essential for cellular functions. These include:

1. mRNA Genes: The primary function of RNA Polymerase II is to transcribe mRNA genes, which are then translated into proteins. mRNA acts as a template for protein synthesis during translation.

2. miRNA Genes: MicroRNAs (miRNAs) are small RNA molecules that regulate gene expression post-transcriptionally. They play important roles in controlling processes like cell differentiation, apoptosis, and response to stress. RNA Polymerase II transcribes these genes into precursor miRNA (pri-miRNA) molecules, which are processed into functional miRNAs.

3. snRNA Genes: Small nuclear RNAs (snRNAs) are involved in RNA splicing, the process of removing introns from pre-mRNA. RNA Polymerase II transcribes snRNA genes, which are essential for the proper maturation of mRNA.

The Correct Answer: D. mRNA, miRNA, and snRNA Genes

Given the options, the correct answer is:

D. mRNA, miRNA, and snRNA genes.

These three types of RNA are transcribed by RNA Polymerase II and play essential roles in gene expression regulation and RNA processing within the cell. RNA Polymerase II is, therefore, central to a variety of cellular functions, from protein synthesis to gene silencing.

What RNA Polymerase II Does Not Transcribe

It’s important to note that RNA Polymerase II does not transcribe certain types of RNA, such as:

• rRNA (ribosomal RNA) and tRNA (transfer RNA) genes, which are transcribed by RNA Polymerase I and RNA Polymerase III, respectively.

• 5S rRNA genes, which are transcribed by RNA Polymerase III.

Summary

Eukaryotic RNA Polymerase II is essential for transcribing mRNA, miRNA, and snRNA genes. By generating mRNA for protein synthesis, miRNAs for gene regulation, and snRNAs for RNA splicing, RNA Polymerase II plays a pivotal role in the regulation of gene expression and cellular function.