Question

question 1 of 10
which of the following must occur before mrna can leave the nucleus in a eukaryotic cell?
i. introns are removed.
ii. exons are spliced together.
iii. exons are removed.
iv. introns are spliced together.
v. a poly - a tail is added to the mrna.
vi. a 5 cap sequence is removed from the mrna.
a. iii, iv, and v
b. i, ii, and v
c. i, ii, and vi
d. iii, iv, and vi

Explanation:

• Introns removal (I): Introns are non - coding regions. They must be removed as they do not code for the final protein product.
• Exons splicing (II): Exons are coding regions. Splicing them together forms a continuous coding sequence for translation.
• Poly - A tail addition (V): The poly - A tail protects the mRNA from degradation and aids in its export from the nucleus and translation initiation.
• Exons removal (III): Incorrect as exons are coding regions and are kept.
• Introns splicing (IV): Incorrect as introns are removed, not spliced together.
• 5' cap removal (VI): Incorrect as a 5' cap is added (not removed) to protect the mRNA and aid in ribosome binding for translation.

Answer:

B. I, II, and V