Wich of the following statements is true with respect to RNA splicing?

Question

1. Exons are removed and introns are connected in the mRNA

2. The first 54 nucleotides are removed from the 5' end and attacheted to the 3' end of the mRNA molecule

3. introns are removed and exons are connected in the mRNA

4. Only the first intron and last exon are removed during splicing

Answer 1

Hi Lauren,

 

mRNA is translated into a polypeptide, therefore, it needs an uninterrupted open reading frame or ORF.

 

ORF is made of exons, the protein coding sequences of pre-mRNA.

 

Exons are separated by introns that might carry regulatory sequence but usually do not encode for protein.  Therefore, introns need to be removed prior to translation of mRNA. Removal of introns  is known as mRNA splicing. With accurate splicing,introns are removed and exons are joined together to form a mature mRNA that is ready to be translated.

 

With such splicing machinery in effect, 3 is the only correct option in above choices. 

 

Hope this helps.