Question

which statement concerning an endosymbiont evolving into a plastid is incorrect?
a) the host cell benefits from sugars produced via photosynthesis carried out by the endosymbiont
b) genetic material from the endosymbiont was moved into the host genome
c) the genome of the endosymbiont remains almost complete and transcriptionally active
d) it was a multi - step process that occurred over millions of years
e) it has occurred independently in multiple lineages

Explanation:

• Option A: In endosymbiosis, the host cell benefits from the products (like sugars from photosynthesis) of the endosymbiont. This is a correct aspect of the relationship.
• Option B: During the evolution of endosymbionts (such as the evolution of plastids from cyanobacteria - like endosymbionts), genetic material is transferred from the endosymbiont to the host genome. This is a well - documented phenomenon.
• Option C: As the endosymbiont evolves into an organelle (plastid), its genome is reduced. Many genes are either lost or transferred to the host genome. So, the genome of the endosymbiont does not remain almost complete and transcriptionally active. This statement is incorrect.
• Option D: The evolution of an endosymbiont into an organelle (plastid) is a multi - step process. For example, there are steps like initial engulfment, establishment of a stable relationship, and genetic integration, which occur over long periods (millions of years).
• Option E: Plastid evolution (endosymbiosis leading to plastids) has occurred independently in multiple lineages. For example, primary endosymbiosis (in plants) and secondary endosymbiosis (in some algae) are different lineages where similar processes of endosymbiosis leading to plastid - like structures have occurred.

Answer:

C. The genome of the endosymbiont remains almost complete and transcriptionally active