During processing of pre-mRNA to mature mRNA, which changes occur?

During processing of pre-mRNA to mature mRNA, which changes occur?

• A. Introns are removed and exons joined
• B. The 5' cap is added
• C. A poly-A tail is added
• D. All of the above

Answer: (D)

During processing of pre-mRNA to mature mRNA, three major changes take place in eukaryotes: a 5' cap is added to the transcript, introns are removed and exons are joined through splicing, and a poly-A tail is added to the 3' end after cleavage. The 5' cap protects the RNA from degradation and helps ribosomes recognize the mRNA for translation. Splicing creates a continuous coding sequence by removing noncoding introns and linking exons together. The poly-A tail enhances stability, aids export from the nucleus, and improves translation efficiency. Because all three modifications occur, the mature mRNA contains these features, so all of the above is the correct answer.

During processing of pre-mRNA to mature mRNA, three major changes take place in eukaryotes: a 5' cap is added to the transcript, introns are removed and exons are joined through splicing, and a poly-A tail is added to the 3' end after cleavage. The 5' cap protects the RNA from degradation and helps ribosomes recognize the mRNA for translation. Splicing creates a continuous coding sequence by removing noncoding introns and linking exons together. The poly-A tail enhances stability, aids export from the nucleus, and improves translation efficiency. Because all three modifications occur, the mature mRNA contains these features, so all of the above is the correct answer.