Question

(7) Which of the following structures is type 1 cap attached to a eukaryotic mRNA? a. m''ppp Sex b. m'G'ppp SXmY C. m’sppp XmYmZ d. None of the above (8). What are cryptic splice sites? a. These are splice sites that are used in some cells, but not in others b. These are splice sites that are always used. c. These are sites that are involved in alternative splicing, resulting in the removal of exons from some mRNA molecules d. These are sequences within exons or introns that resemble consensus splicing signals, but are not true splice sites.

Answer 1

7b.

Most capped eukaryotic mRNAs have a single methyl group on the terminal G residue at the N-7 position, whereas adjacent nucleotides can be 2′-O-methylated to different extents, providing a basis for cap nomenclature: m⁷GpppN (Cap 0), m⁷GpppNm (Cap 1), and m⁷GpppNmpNm (Cap 2).

8d. These are sequences within exons or introns that resemble consensus splicing signals but are not true splice sites.

A cryptic splice site is an mRNA sequence that has the potential for interacting with the spliceosome. Cryptic splice sites also match the consensus motifs, and they are splice sites that are not used in wild-type pre-mRNA but are only selected as a result of a mutation elsewhere in the gene, most often at the authentic splice site.