Which one of the following can be inferred from the passage about the absence of cell walls in some bacteria?

avif on July 7, 2020

C vs. E

I struggled on this one and I ended up picking E. Am I misunderstanding what horizontal transmission means? I thought it was used anytime that a trait was passed on without a change in the genetic structure. Doesn't this qualify?

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shunhe on July 17, 2020

Hi @avif,

Thanks for the question! So remember this question: it’s asking us what can be inferred from the passage about the absence of cell walls in some bacteria. Can we infer that it can be transmitted horizontally to other bacteria? Well no, not quite. There’s two types of genes, remember (lines 46-47). Most are inherited vertically, but some can be acquired horizontally. But we don’t know which group the gene concerning the absence of cell walls is in; the passage doesn’t say anything about it. So we can’t infer that the absence of cell walls in some bacteria can be transmitted horizontally; that goes beyond what the passage tells us. And so (E) is unsupported and wrong.

Now take a look at (C), which tells us that it can be caused by the loss of a cell wall in a single bacterium. Well, take a look at lines 15-19. That’s exactly what that describes; an experimenter removes the cell wall from a bacterium (one bacteria) and the bacterium continues to grow and multiply indefinitely without walls. So that exactly describes something in the passage, and so (C) can be inferred from the passage.

Hope this helps! Feel free to ask any other questions that you might have.