Video Transcript
Consider this messenger RNA. The blue sequence is commonly called the untranslated region, UTR, and finishes right
before the start codon, shown in red. What does this UTR sequence contain? (A) The UTR sequence contains the DNA polymerase binding site. (B) The UTR sequence contains the mitochondrial binding site. (C) The UTR sequence contains the ribosome binding site. (D) The UTR sequence contains the DNA binding site.
You may recall that a gene in DNA can be converted into a protein in a couple of
steps. The first step is transcription, where the gene is copied to make an mRNA
transcript. Then, the sequence of nucleotides in mRNA is translated into a sequence of amino
acids to form a polypeptide, which can then fold to form a protein. During translation, the mRNA binds to the ribosome. The ribosome matches three nucleotide segments of the mRNA, called codons, with
specific amino acids.
In the mRNA sequence in this question, we can see one of these codons here in
red. This is called a start codon because this is where translation begins. The start codon actually codes for the amino acid methionine. After the start codon, each codon is matched to its specific amino acid until
translation is complete and the polypeptide is released.
The five prime end of the mRNA that precedes the start codon is the untranslated
region, or the UTR. This site contains the ribosome binding site that allows the mRNA to bind to the
ribosome. Therefore, the option that best describes what the UTR sequence contains is given by
answer choice (C). The UTR sequence contains the ribosome binding site.
