Final answer:
The complementary bases on the mRNA strand to the DNA strand ACAGT are UGUCA, as dictated by the base pairing rules where adenine pairs with uracil and cytosine pairs with guanine.
Step-by-step explanation:
The correct answer to the question regarding the complementary bases on the mRNA strand if one strand of DNA contains the bases ACAGT is c.) UGUCA. This is because during transcription, adenine (A) pairs with uracil (U) in mRNA instead of thymine, cytosine (C) pairs with guanine (G) as usual, and guanine (G) pairs with cytosine (C). Therefore, each DNA base has a corresponding mRNA base: A to U, C to G, and G to C. Since thymine (T) is not found in RNA, it is replaced by uracil (U).
When the cell transcribes DNA into mRNA during gene expression, it must create a complementary mRNA strand. This involves base pairing rules which are similar but slightly different from DNA replication. The enzyme RNA polymerase reads the DNA template strand and synthesizes the mRNA strand, creating a molecule that can then be used in the process of translation to synthesize proteins.