Ans.
Protein synthesis involves formation of proteins, during which information present in DNA is used to make polypeptide chains. Hence, amino acid sequence of a polypeptide chain is determined by the sequence that may differ in different species having proteins with same amino acid sequence.
Thus, the molecules that are used to compare different species with proteins having exact same amino acid sequences are DNA molecules.
Protein synthesis includes two steps, transcription and translation. During transcription, DNA gets converted into RNA by RNA polymerase enzyme, while during translation, RNA provides information to make proteins.
In RNA information is present as triplets of nucleotides, known as codon. Each code codes for a specific amino acid. There are a total of 64 codons, while number of protein-forming amino acids is 20. Hence, one amino acid can be coded by more than one codon and this property of codons is known as degeneracy of codons.
Thus, two species may have the same protein even if their DNA molecules are different because of degeneracy of codons.
