What kind of data likely convinced biologists that photosynthesis in Paulinellao

Question

What kind of data likely convinced biologists that photosynthesis in Paulinellaoriginated independently of the endosymbiotic events that gave rise to chloroplasts in green algae?

Question 4 options:

Nucleotide sequences of genes in the chloroplasts of Paulinella show that these organelles are most closely related to cyanobacteria different from those that gave rise to chloroplasts.

Paulinella has a chloroplast that arose by means of a secondary endosymbiotic event incorporating a photosynthetic eukaryote.

Paulinella is not closely related to green algae, and each other photosynthetic eukaryotic group is closely related to green algae.

Green algae have cell walls made of cellulose, but Paulinella does not.

Nucleotide sequences of genes in the chloroplasts of Paulinella show that these organelles are most closely related to cyanobacteria different from those that gave rise to chloroplasts.

Paulinella has a chloroplast that arose by means of a secondary endosymbiotic event incorporating a photosynthetic eukaryote.

Paulinella is not closely related to green algae, and each other photosynthetic eukaryotic group is closely related to green algae.

Green algae have cell walls made of cellulose, but Paulinella does not.

Explanation / Answer

Ans. #4. Correct option- A. The molecular studies/ DNA sequencing indicates that the chloroplast of Paulinella is closely related to Prochlorococcus and Synechococcus groups of cyanobacteria, than the usual cyanobacteria group from which plastids of green plants/algae evolved.

# Option B- Incorrect. Paulinella chloroplast also arose from primary endosymbiosis, the difference is the that the prey cyanobacteria (that developed into chloroplast) in Paulinella and green plants/algae belong to different groups.

# Option C- Incorrect. The statement is true because the molecular studies reflects so. The basis of this “difference” is comparative molecular studies of the chloroplast in Paulinella and green algae. Without that, the difference couldn’t be established. So, option A is most appropriate.

# Option D- Incorrect. The statement is true- green algae cell wall is made of cellulose but Paulinella (amoeba) lacks it. However, presence or absence of cell wall (type) is not sufficient to differentiate the origin of chloroplast in the two groups, green algae and Paulinella. The difference is established using molecular studies. So, option A is most appropriate.

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