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VR10. Scientific and Factual Passages – Homework (Part 3)
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Section Breakdown
| Your Score | Average of all Users | Percentile | |
|---|---|---|---|
| Scientific/Factual Questions - Tutoring (Medic Mind) |
Scientific/Factual Questions - Tutoring (Medic Mind)
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Average score:
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Now that we’ve gone through the theory on scientific/factual passages questions, it’s time to see if you have learned what we have taught you – Let’s now tackle some questions together.
Towards the end of the nineteenth century, chromosomal abnormalities detected under the light microscope revealed that a type of massive genome instability resulting in an abnormal number of chromosomes occurs in certain types of cancer. Not long after, the biochemist Otto Warburg observed that tumour cells tend to use pathways of glucose and energy metabolism that are distinct from those used by normal cells. We now know that genome instability and altered metabolism are two common characteristics of most tumour cells. Genome instability has been investigated continuously since its discovery; altered metabolism was rediscovered as a research area only recently. But not much crosstalk between these two processes in cancer has been reported so far. Writing in Nature, Sulkowski et al. reveal how several metabolites that accumulate to high levels in tumour cells suppress DNA repair, thus revealing a direct link between altered metabolism and genome instability caused by DNA damage.
Mutations targeting the genes encoding the enzymes isocitrate dehydrogenase 1 and 2 (IDH1 and IDH2) result in cells accumulating high levels of the metabolite 2-hydroxyglutarate (2-HG). Mutations in the genes encoding the enzymes fumarate hydratase and succinate dehydrogenase cause cells to accumulate high levels of the molecules fumarate and succinate, respectively. These three small molecules are often referred to as oncometabolites because their accumulation boosts tumour development, and they are structurally similar to the molecule α-ketoglutarate (α-KG). This is an intermediate in the Krebs-cycle pathway that also serves as a component, called a co-substrate, needed for the function of a family of enzymes called α-KG/Fe(II)-dependent dioxygenases.
(Adapted from Nature, https://www.nature.com/articles/d41586-020-01569-1)
Explanation
This is type 1 specific question about the common features of tumour cells according to the passage. Remember that in these scientific/factual passages, the keywords will be very important and synonyms to a lesser degree, because you are not expected to know synonyms for the technical language used. Scan the text for any mention of common features of tumour cells, and if you are struggling you can use keywords from the statements themselves to find mention.
Statement A is the correct answer, which is clear if you managed to find the section which lists genome instability and altered metabolism as the two most common characteristics of tumour cells. If you couldn’t find that, don’t panic and search for the statement itself in the text. This would also lead you to the part of the passage discussing common changes.
Statement B has the excellent keyword IDH1, which should quickly draw your eye to the opening of the second paragraph. This mentions that such mutations can cause chemical accumulation, but because the text does not mention how common such mutations are you could safely skip this and assume it is untrue.
Statement C has the key phrase ‘Krebs cycle’. This is found late in the second paragraph, but it is mentioned offhand as part of a different explanation of a chemical pathway. Therefore, you can assume that it is not discussed as part of the topic in the question stem.
Statement D has the keyword ‘oncometabolite’, which is to be found in the second paragraph. Again, this is not discussed in the all-important context of the question stem, so it is not the correct answer.
Factual passage tip!
Remember that factual passages have excellent keywords and are often not designed for you to fully understand. When reading any scientific passage, you will usually have your own questions that you want to answer so what you are doing here is no different. Seek out the section answering your question, and assess the statements.