Question

If the anticodon for lysine is UUU, what is its codon?

Answer 1

The codon of lysine which has an anticodon of UUU is AAA. Codon consists of $3$ nucleotide bases. U represents Uracil. The complementary base of Uracil is Adenine. Adenine is represented by A. Uracil base is found only in RNA in place of Thymine that is present in DNA.AAG also codes for lysine.

Complete answer:
Codons are the trinucleotide sequence that is essential for the production of specific amino acids. Sometimes codons also send the signal for the termination of translation of the gene. Codons are mainly present in the mRNA.
Anticodons are the trinucleotide sequence that is embedded in tRNA which is complementary to the codons. The function of the anticodon is pairing with codon and ensuring the correct addition of amino acid to the polypeptide chain.
Nucleotides are nitrogen-containing bases that are attached to a phosphate group and a ribose or deoxyribose sugar moiety.
There are $5$ types of nucleotides – Adenine (A), Guanine(G), Thymine (T), Cytosine (C), Uracil(U). The base Uracil is replaced by Thymine (found in DNA) in the case of RNA. The bases Adenine- Thymine, Adenine – Uracil, Guanine- Cytosine are complementary to each other and form bonds among themselves. As the anticodon contains a trinucleotide sequence of Uracil bases (U) hence its complementary trinucleotide sequence which will act as codon in this case will be trinucleotide of Adenine (A) base.

Hence the codon will be AAA.

Note:
There are $64$ codons among which only $61$ codons code for the amino acid rest are stop codons. There are $20$ amino acids and these are encoded by the $61$ codons. So it can be said that one amino acid is indicated by more than one codon. The anticodon UUU if used as a codon will code for the amino acid phenylalanine.