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Multiple Choice
Which of the following modifications occur to mRNA before it leaves the nucleus in eukaryotic cells?
A
Conversion to DNA
B
Addition of introns
C
Removal of the 5' cap
D
Addition of a 5' cap and poly-A tail
Verified step by step guidance
1
Understand that mRNA processing is a crucial step in eukaryotic gene expression, ensuring that the mRNA is mature and ready for translation.
Recognize that the initial mRNA transcript, known as pre-mRNA, undergoes several modifications before it exits the nucleus.
Learn that one of the key modifications is the addition of a 5' cap, which is a modified guanine nucleotide added to the 5' end of the mRNA. This cap protects the mRNA from degradation and assists in ribosome binding during translation.
Identify another important modification: the addition of a poly-A tail. This involves adding a sequence of adenine nucleotides to the 3' end of the mRNA, which also helps protect the mRNA from enzymatic degradation and aids in the export of the mRNA from the nucleus.
Note that introns are removed from the pre-mRNA during a process called splicing, leaving only the exons, which are the coding sequences that will be translated into protein.