Step 1: Understanding the problem.
We are asked to find the number of three-letter words that can be formed from the letters of the word 'VIRUS' without repetition. The word 'VIRUS' contains 5 distinct letters: V, I, R, U, and S.
Step 2: Calculating the number of arrangements.
The number of ways to choose 3 letters from 5 distinct letters is given by the number of permutations of 3 letters from 5. This is calculated as:
\[
P(5, 3) = \frac{5!}{(5-3)!} = \frac{5!}{2!} = \frac{5 \times 4 \times 3}{1} = 60
\]
Step 3: Conclusion.
The correct answer is (C) 60, as there are 60 possible three-letter words that can be formed.
Identify the taxa that constitute a paraphyletic group in the given phylogenetic tree.
The vector, shown in the figure, has promoter and RBS sequences in the 300 bp region between the restriction sites for enzymes X and Y. There are no other sites for X and Y in the vector. The promoter is directed towards the Y site. The insert containing only an ORF provides 3 fragments after digestion with both enzymes X and Y. The ORF is cloned in the correct orientation in the vector using the single restriction enzyme Y. The size of the largest fragment of the recombinant plasmid expressing the ORF upon digestion with enzyme X is ........... bp. (answer in integer) 