Final answer:
Retrotransposons lack the env gene that encodes the envelope protein found in retroviruses. Instead, they may use a Gag protein for encapsulation, but do not form infectious viral particles. Therefore, the statement is false; retrotransposons do not have an env gene like retroviruses.
Step-by-step explanation:
The question revolves around a comparison between retroviruses and retrotransposons, particularly regarding the presence of an env gene. Retroviruses, such as HIV, typically have an env gene that encodes for an envelope protein surrounding the viral DNA. This envelope is essential for the virus's ability to infect host cells. However, retrotransposons, although they share many similarities with retroviruses, including reverse transcriptase and integrase enzymes, lack this env gene. Instead, they may contain a Gag protein that forms a virus-like particle.
Examples of retrotransposons include the yeast Ty element, which uses Gag instead of an env-encoded envelope protein for encapsulation during retrotransposition. Retrotransposons replicate within the nucleus of a cell, in contrast to retroviruses which need to infect a host cell. Retrotransposons can resemble viruses to some extent, but they do not form infectious particles that exit the host cell, as retroviruses do. Consequently, the correct answer to the question is (b) false; retrotransposons do not have the env gene similar to retroviruses.