Chapter 8, Problem 15P

Summary Introduction

To analyze:

Four introns labeled A to D are present in eukaryotic gene ($\text{Gen-100}$). Consider that $\text{Gen-100}$ has been isolated and the DNA of the gene ($\text{Gen-100}$) has been denatured. Then it is mixed with polyadenylated mRNAfrom the gene.

a. The R-loop structure, seen with electron microscopy is to be illustrated.

b. The introns are to be labelled.

c. Single stranded or double stranded, intron region is to be determined.

Introduction:

DNA contains coding and non-coding regions called exons and introns respectively. During post-transcriptional modifications of eukaryotic DNA, the introns are spliced out and mature mRNA is synthesized containing only exons. R-looping was first discovered and described in $1976$ by Richard. J. Roberts and Philip A. Sharp. R-loop is a three-stranded structure. It is composed of a hybrid of RNA: DNA and the single-stranded non-template DNA. The R-loops are created in the laboratory by hybridization of mature mRNA and double-stranded DNA. The intronicregion of DNA gets spliced out from the mRNA and forms single-stranded structure as they cannot hybridize with the dsDNA.The spliced intronic regions will form the loops between the exons. These R-loops are observed by electron microscopy.