Question

Q1 An RNA was hybridized with it’s own gene. The electron micrograph showed 5 single stranded loops. Identify the statements as true or false.

A. The single stranded loops are created by exons in the mRNA

B. The single stranded loops are created by introns in the gene

C. The loops are created because the introns are missing in mRNA

D. The result shows the presence of 5 genes

E. The result shows the presence of 5 introns in the gene

F. The result shows the presence of 5 exons in the gene

G. The exons in both the gene and the mRNA are hybridizing but the introns in the gene don’t have complementary regions in mRNA, so they loop out

Answer 1

A. The single stranded loops are created by exons in the mRNA - FALSE - This statement is false as exons are present in both mRNA and DNA and are complementary, so, they would form double-stranded hybrid regions and will not form single-stranded loops.

B. The single stranded regions are created by introns in the gene - TRUE - This statement is true as the gene (DNA) contains introns which are not present in the mRNA as its introns have already been spliced out. So, when DNA-RNA hybridisation occurs, the intron parts of the gene which do not have any complementary regions in mRNA, will form single-stranded loops.

C. The loops are created as introns are missing in mRNA - TRUE - This statement is true as the loops are formed as the introns in the gene do not have complementary intron region in the mRNA as the introns in mRNA have been removed by splicing.

D. The result shows the presence of 5 genes - FALSE- This statement is false because each loop corresponds to an intron and not a gene.

E. The result shows the presence of 5 introns in the gene - TRUE - This statement is true because each loop corresponds to an intron in the gene which was unable to pair with its complementary intron region in the mRNA as they have been removed by splicing. 5 single stranded loops were observed. So, there are 5 introns in the gene.

F. The result shows the presence of 5 exons in the gene - FALSE - The statement is false as the loops correspond to introns and not exons.

G. The exons in both the gene and the mRNA are hybridizing but the introns in the gene don't have complementary regions in mRNA , so they loop out - TRUE - This statement is true. Exons are present in both gene and mRNA so, being complementary, they hybridize. However, introns of mRNA have been removed by splicing but are present in the gene. So, the introns of gene do not have any complementary region in the mRNA and cannot hybridize so, they form single-stranded loops.