Final answer:
Option b is correct; during transcription, DNA codes for mRNA, which then codes for polypeptides during translation according to the Central Dogma of molecular biology.
Step-by-step explanation:
The Central Dogma of molecular biology describes the flow of genetic information from DNA to mRNA to protein. The correct answer to the student's query is that during transcription, DNA codes for mRNA, which then codes for polypeptides during translation. The process of transcription involves the synthesis of mRNA from a DNA template, and translation involves the decoding of the mRNA sequence to form a polypeptide, the building block of proteins.
In other words, the Central Dogma explains that DNA encodes RNA; RNA then encodes protein. The copying of information from DNA to RNA is a direct process, where each DNA nucleotide corresponds to a complementary RNA nucleotide.
Subsequently, every three nucleotides on the mRNA, known as a codon, correspond to one amino acid in the protein. This systematic conversion from nucleotide language to amino acid language occurs during translation in the ribosome, with the help of tRNA and rRNA.