Question

If mRNA is complementary to the DNA template strand and the DNA template strand is complementary to the DNA nontemplate strand, then why are base sequences of mRNA and the DNA nontemplate strand not identical? Could they ever be?

a) No, they cannot be identical due to differences in transcription and translation processes.
b) Yes, they are identical, as both are synthesized during the same process.
c) No, they are not identical because RNA polymerase synthesizes mRNA from the coding DNA strand.
d) Yes, they are identical as they both serve as templates for protein synthesis.

Answer 1

The base sequences of mRNA and the DNA non-template strand are nearly identical except for the substitution of uracil (U) in mRNA where thymine (T) is found in DNA.

Step-by-step explanation:

The base sequences of mRNA and the DNA non-template strand are not identical because, during transcription, uracil (U) is used in RNA instead of thymine (T) which is found in DNA. When the mRNA is synthesized, it is complementary to the DNA template strand. This means that wherever there is an adenine (A) in the DNA template, uracil (U) is placed in the mRNA, and vice versa. By contrast, the DNA non-template strand, also known as the coding strand, contains thymine (T) where the mRNA has uracil (U). Therefore, while the mRNA is almost identical to the DNA non-template strand, it differs in that uracil substitutes for thymine.