Scientists identified two distinct pathogens in blood samples taken from mice. They analyzed both pathogens in the laboratory and recorded the presence or absence of certain characteristics in the table below (NOTE: + indicates presence and − indicates absence). They concluded that both pathogens are prokaryotic cells. Do the data support this conclusion?

Question

Scientists identified two distinct pathogens in blood samples taken from mice.  They analyzed both pathogens in the laboratory and recorded the presence or absence of certain characteristics in the table below (NOTE: + indicates presence and − indicates absence).  They concluded that both pathogens are prokaryotic cells.  Do the data support this conclusion?

Quizplus · Accepted Answer

11ecba2d_103a_6662_a3bf_e58359c584be_MD0008_00 Disease-causing pathogens may be classified as eukaryotic cells, prokaryotic cells, or viruses. Viruses are unique in that they are obligate intracellular parasites that rely on host cells to reproduce. Accordingly, viruses lack the transcriptional and translational machinery found in all prokaryotic and eukaryotic cells. In addition, while the genomes of all prokaryotic and eukaryotic cells are always composed of DNA, viruses may contain either DNA or RNA (eg, +ssRNA virus, retrovirus) genomes. In this scenario, researchers identified two distinct pathogens in blood samples taken from mice. After laboratory analysis, they recorded the presence or absence of certain characteristics in each pathogen. The data show that pathogen A lacks ribosomes, a characteristic that is unique to viral pathogens. Because all prokaryotic cells contain ribosomes, pathogen A cannot be a prokaryotic cell and is most likely a virus. (Choice A) In contrast to eukaryotic cells, membrane-bound organelles are absent in all prokaryotic cells. However, viruses also lack membrane-bound organelles, so the absence of membrane-bound organelles alone is not sufficient to conclude that both pathogens are prokaryotic. (Choice C) DNA genomes are found in all eukaryotic and prokaryotic cells, as well as in some viruses. Therefore, the presence of a DNA genome does not necessarily indicate that a pathogen is prokaryotic. (Choice D) Generally, prokaryotic cells and some eukaryotic cells (eg, fungi and plant cells) are surrounded by a protective cell wall. Accordingly, the presence of a cell wall in pathogen B indicates that the pathogen could be either prokaryotic or eukaryotic. However, because pathogen A does not have a cell wall, it is unlikely to be a prokaryotic cell. Educational objective: In contrast to eukaryotic cells, prokaryotic cells and viruses lack membrane-bound organelles. However, viruses are unique in that they may possess DNA or RNA genomes and lack the transcriptional and translational machinery (eg, ribosomes) found in prokaryotic and eukaryotic cells.

Scientists Identified Two Distinct Pathogens in Blood Samples Taken from Mice