Question

which of the following is the best explanation of the role of dna and rna in making proteins?
a. dna unwinds into two separate strands, and an exact copy of each is produced during replication. during translation, a dna strand is used to produce a complementary strand of mrna, with uracil taking the place of thymine. during transcription, each set of three codons in the mrna results in an amino acid being added to a chain, and a protein is formed.
b. dna unwinds into two separate strands, and a complementary copy of each is produced during replication. during transcription, a dna strand is used to produce a complementary strand of mrna with uracil taking the place of adenine. during translation, each base in the mrna results in an amino acid being added to a chain, and a protein is formed.
c. dna unwinds into two separate strands, and a complementary copy of each is produced during replication. during transcription, a dna strand is used to produce a complementary strand of mrna with uracil taking the place of thymine. during translation, each set of three bases in the mrna results in an amino acid being added to a chain, and a protein is formed.
d. dna unwinds into two separate strands, and an exact copy of each is produced during replication. during transcription, a dna strand is copied to produce mrna, which is an exact copy of the dna strand except that uracil takes the place of thymine. during translation, each set of three bases in the mrna results in a protein with a specialized function being formed.

Explanation:

DNA replication involves unwinding into two strands and making complementary copies. Transcription uses a DNA strand to make a complementary mRNA strand where uracil replaces thymine. Translation involves sets of three - base codons in mRNA adding amino - acids to a chain to form a protein. Option C correctly describes these processes. Option A has incorrect terminology in the order of transcription and translation steps. Option B has incorrect base - substitution information (uracil replaces thymine, not adenine). Option D has incorrect description of mRNA as an exact copy of DNA (it is complementary).

Answer:

C. DNA unwinds into two separate strands, and a complementary copy of each is produced during replication. During transcription, a DNA strand is used to produce a complementary strand of mRNA with uracil taking the place of thymine. During translation, each set of three bases in the mRNA results in an amino acid being added to a chain, and a protein is formed.