Endosymbiotic theory Knowledge-Based Practice

Questions

1. 1.

   Which of the following observations regarding the replication and division of mitochondria and chloroplasts provides evidence for their endosymbiotic origin?

   • A) They are synthesized de novo from the endoplasmic reticulum during each eukaryotic cell cycle.
   • B) They divide independently of the host cell nucleus through a process resembling bacterial binary fission.
   • C) They replicate their genetic material through eukaryotic mitosis alongside nuclear chromatin.
   • D) They bud directly from the trans-Golgi network following vesicular protein transport.
2. 2.

   Which of the following features of mitochondrial protein synthesis provides direct functional evidence supporting the endosymbiotic theory?

   • A) Initiation of translation with unmodified methionine
   • B) Translation occurring primarily on 80S cytoplasmic ribosomes
   • C) Sensitivity of translation to antibacterial antibiotics such as chloramphenicol
   • D) Complete inhibition of organellar translation by cycloheximide
3. 3.

   According to phylogenetic and molecular evidence supporting the endosymbiotic theory, which free-living prokaryotic lineages gave rise to mitochondria and chloroplasts, respectively?

   • A) Methanogenic archaea and cyanobacteria
   • B) Spirochetes and alphaproteobacteria
   • C) Cyanobacteria and alphaproteobacteria
   • D) Alphaproteobacteria and cyanobacteria
4. 4.

   According to the serial endosymbiotic theory, which statement explains why the acquisition of mitochondria is considered to have occurred before the acquisition of chloroplasts during eukaryotic evolution?

   • A) All photosynthetic eukaryotes with chloroplasts also contain mitochondria, whereas many mitochondriate eukaryotes lack chloroplasts.
   • B) Chloroplasts rely entirely on host nuclear genes for protein synthesis, whereas mitochondria produce all of their own proteins independently.
   • C) Mitochondria originated from anaerobic archaea, whereas chloroplasts originated from aerobic proteobacteria.
   • D) Chloroplast ribosomes are structurally identical to eukaryotic cytoplasmic 80S ribosomes, whereas mitochondrial ribosomes are 70S.
5. 5.

   Which of the following structural characteristics of mitochondria provides direct evidence supporting the endosymbiotic theory?

   • A) Presence of linear chromosomes associated with histone proteins
   • B) Possession of a single phospholipid monolayer surrounding the matrix
   • C) Presence of circular DNA molecules and 70S ribosomes similar to those in bacteria
   • D) Ability to synthesize all required enzymatic proteins independently of the cell nucleus

Answers and step-by-step solutions appear after you finish the test.