Final answer:
A U nucleotide in an mRNA codon would bind to an adenine (A) in a tRNA anticodon. The tRNA recognizes the mRNA codon specified by its anticodon, regardless of modifications to the amino acid it carries.
Step-by-step explanation:
Which nucleotide in a tRNA anticodon would bind to the U nucleotide in an mRNA codon? The answer is straightforward: in mRNA, each nucleotide pairs with its complement, so adenine (A) pairs with uracil (U), cytosine (C) pairs with guanine (G), and vice versa. Given this, a U nucleotide in an mRNA codon would pair with an adenine (A) nucleotide in the tRNA anticodon.
In the context of a tRNA carrying a modified amino acid, the tRNA will still recognize the codon specified by its anticodon on the mRNA, regardless of the amino acid modification. Therefore, the anticodon will match the codon in mRNA, not the modified amino acid it carries. The anticodon consecutive sequence is specifically designed to pair with the mRNA codon and does not change if the attached amino acid is chemically modified.