Final answer:
The corresponding pre-mRNA could be as large as 2 million nt long. Before mRNA leaves the nucleus, it undergoes extensive processing, including splicing to remove non-coding regions and stitching together coding regions called exons. This process leads to a larger variety of possible proteins and protein functions.
So, the correct answer is 3.
Step-by-step explanation:
Before the mRNA molecule leaves the nucleus and proceeds to protein synthesis, it undergoes extensive processing. This processing involves the removal of non-coding regions called introns through a process called splicing. The remaining coding regions called exons are then pasted together to form the mature mRNA molecule. This process of splicing can result in multiple variations of the protein, leading to a larger variety of possible proteins and protein functions.
In addition, there are other processes involved in pre-mRNA maturation such as the addition of stabilizing and signaling factors at the 5' and 3' ends of the molecule, as well as the addition of a poly-A tail to protect the mRNA from degradation. These additional steps contribute to the larger size of the pre-mRNA compared to the mature mRNA.
So, the correct answer is 3) could be as large as 2 million nt long.
Complete question:
If a mature human mRNA is 14,000 nt long, the corresponding pre-mRNA
- could not be larger than 14.000 nt long
- could not be larger than 100.000 nt long
- could be as large as 2 million nt long
- would not exist, as no human mRNA is known that is as big as 14,000 nt
- would have mutant splicing signals.