Solutions For An Introduction to Genetic Analysis Chapter 15 Problem 4P

The phenomenon of which a genetic element (transposon) moves from one place to another place within a genome is called Transposition. Retrotransposition is transposition of a transposon through an RNA (Ribo Nucleic Acid) intermediate. The mechanism of retrotransposition is depicted in figure 1 as shown below:

The process of retrotransposition is explained in the following steps:

• A nick is created within the target site of one of the strands

• The L₁ RNA (long terminal repeat RNA) anneals to the broken strand at complementary sites

• Reverse transcriptase enzyme adds nucleotides to the 3’ OH group of the broken strand, complementary to that of the L₁ RNA

• Parallel to this, nick is created on the other strand also, leading to another free 3’OH

• Nucleotides complementary to the newly synthesized strand are added to the free 3’OH

• Nicks are sealed and the genome (genomic region) has a retrotransposon with duplicated target sites

• As the transposon addition is directed by an RNA molecule (L₁ RNA here), this process is called retrotransposition