The eukaryotic gene Gen-100 contains four introns labeled A to D. Imagine that Gen-100 has been isolated and its DNA has been denatured and mixed with polyadenylated mRNA from the gene.

Illustrate the R-loop structure that would be seen with electron microscopy.

Key Concepts

R-loop Structure

An R-loop is a three-stranded nucleic acid structure formed when RNA hybridizes with a complementary DNA strand, displacing the non-template DNA strand. This occurs during transcription when mRNA is synthesized from a DNA template. The R-loop can be visualized using electron microscopy, revealing the regions where RNA is bound to DNA, which is crucial for understanding gene expression and splicing.

Introns and Exons

Introns are non-coding sequences within a gene that are transcribed into pre-mRNA but are removed during RNA splicing. Exons, on the other hand, are the coding sequences that remain in the mature mRNA and are translated into proteins. Understanding the roles of introns and exons is essential for interpreting the R-loop structure, as the presence of introns affects the hybridization pattern between mRNA and DNA.

Polyadenylated mRNA

Polyadenylated mRNA refers to messenger RNA that has a poly(A) tail added to its 3' end, which is crucial for mRNA stability, export from the nucleus, and translation efficiency. In the context of the R-loop, polyadenylated mRNA is used to hybridize with the denatured DNA, allowing for the visualization of the R-loop structure. This feature is important for understanding the functional aspects of gene expression.