Video Transcript
In eukaryotes, the process of transcription produces pre-mRNA. Which of the following processes is involved in converting this pre-mRNA into mRNA,
ready for translation? (A) Splicing, (B) mitosis, (C) methylation, (D) duplication, (E) mutation.
In order for a gene in DNA to be converted into a protein, it needs to go through a
couple of steps. The first step is transcription and involves the gene being copied to form an mRNA
transcript. The second step is translation and involves the nucleotide sequence in mRNA being
converted into a sequence of amino acids to form a polypeptide. This polypeptide can then go on to fold into a protein with a specific function.
This question is asking us about transcription and producing mature mRNA from
pre-mRNA, so let’s look at this in more detail. Once mRNA is transcribed from DNA, it can undergo posttranscriptional processing to
produce a mature mRNA that’s ready for translation. One processing event is the addition of a cap sequence to the five prime end of
mRNA. This is a modified guanine nucleotide that helps stabilize the mRNA. Another modification is the addition of a string of adenine nucleotides, sometimes
called a poly-A tail. This is called polyadenylation.
The final modification we’ll discuss is splicing. If we look at a gene in DNA, there are parts of the gene that aren’t involved in
coding for a protein. These sequences are called introns. These introns are carried over during transcription into pre-mRNA and need to be
removed during processing. During splicing, these introns are cut, or spliced, out of the pre-mRNA sequence.
Notice how the length of mRNA is now shorter after these sequences have been
removed. Now the sequence of mRNA consists mostly of protein coding sequence to form a
polypeptide. This mRNA is now mature and is ready to exit the nucleus where it can be translated
into a protein sequence.
To go back to our question, the process that is involved in converting pre-mRNA into
mRNA is given by answer choice (A) splicing.
