44. The "UK variant"--lineage B.1.1.7 of SARS-CoV-2 has raised widespread concern these days. In the UK variant, several nuclcotide mutations were found on the receptor-binding domain (RBD) of viral spike protein, but only one amino acid change N501Y was characterized. Please explain why other RBD nucleotide mutations are silent?

45. All eukaryotes have three different RNA polymerases. Match the name of each RNA polymerases in Column I to its correct description in Column II. Options from Column I can be used more than once. Column I (1) RNA polymerasc I (2) RNA polymerase II (3) RNA polymerase III Column II A. Transcribing the genes for the two large rRNA molecules. B. Transcribing most eukaryotic genes that encode proteins. C. Transc cribing the genes for 5S rRNA and other small RNA molecules. D. Transcribing the genes for tRNA.

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