Final answer:
The correct answers are options A,D and F.Eukaryotic pre-mRNAs are modified by splicing of introns, adding a poly-A tail at the 3'-end, and a 7-methyl guanosine cap at the 5'-end.
Step-by-step explanation:
The modifications that occur to eukaryotic pre-mRNAs are essential for the stability and functionality of the resultant mRNAs. Two key modifications are the addition of a 5' cap and a 3' poly-A tail. The 5' cap consists of a 7-methyl guanosine moiety added to the 5' end of the pre-mRNA. This cap protects mRNA from degradation and is important for the initiation of translation. The 3' poly-A tail is a sequence of adenine nucleotides added to the 3' end after transcription, which also helps to stabilize the mRNA and regulate its export from the nucleus.
In addition to these cap and tail modifications, splicing of introns (non-coding sequences) occurs, resulting in the joining of exons (coding sequences) to form the mature mRNA ready for translation. Therefore, the correct options for the modifications that occur to eukaryotic pre-mRNAs are:
- Splicing of introns
- Poly-A tail at the 3'-end
- 7-methyl guanosine cap at the 5'-end