Final answer:
mRNA transcripts are most affected by low levels of α-amanitin since they are primarily produced by RNA polymerase II, which is extremely sensitive to the toxin.
Step-by-step explanation:
The transcripts that will be most affected by low levels of α-amanitin are those produced by RNA polymerase II, which include mRNA transcripts. α-amanitin is a toxin found in the poisonous mushroom Amanita phalloides, and it inhibits RNA synthesis in animals by affecting eukaryotic RNA polymerases differently. RNA polymerase I is completely insensitive to α-amanitin, RNA polymerase II is extremely sensitive, and RNA polymerase III is moderately sensitive.
Considering RNA polymerase II transcribes the vast majority of genes, mRNA is the kind of RNA most affected. In contrast, rRNA is primarily transcribed by RNA polymerase I, tRNA by RNA polymerase III, and snRNA also by RNA polymerase II but to a lesser extent than mRNA.