Video Transcript
The diagram provided outlines the main stages of transcription in an incorrect
order. Use the letters to state the correct order.
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 to put the steps of transcription, as shown in the
provided diagram, into the correct order. So let’s look at transcription in a bit more detail.
The major enzyme of transcription is called RNA polymerase, and it first binds to the
promoter region of a gene in DNA. This is indicated by step W in the provided diagram, so we’ll mark this with the
number one.
Next, RNA polymerase unwinds, or unzips, the double-stranded DNA molecule. It does this by breaking the hydrogen bonds between base pairs. This is indicated by step Y in our provided diagram.
Now that the bases on DNA are exposed, free RNA nucleotides can be added to form a
complementary strand of mRNA. This is step Z on the left.
This process continues as RNA polymerase moves along the DNA. Along the way, the double helix is unzipped and new RNA nucleotides are added to the
growing mRNA. Once a stop signal is reached, the mRNA is released so it can exit the nucleus to be
translated into a polypeptide, which can then fold into a protein. These final steps are indicated by step X on the left.
Therefore, the correct order for the main stages of transcription is given by W, Y,
Z, X.
