Video Transcript
In a eukaryotic cell, what happens to a strand of mRNA once it is formed? (A) It binds to other mRNA strands and forms a complex protein molecule. (B) It is packaged in vesicles and transported to the Golgi apparatus. (C) It is broken down into its component nucleotides. (D) It leaves the nucleus through the nuclear pores. (E) It leaves the cell through the cell membrane.
In order for a gene in DNA to be converted into a protein with a specific function,
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.
Both transcription and translation occur in different parts of the cell, so let’s
look at that in a bit more detail. Let’s say that this gene, indicated in pink in the cell’s DNA, is to be converted
into a protein. This gene is first transcribed into mRNA in the nucleus of the cell. This mRNA can undergo processing in the nucleus. And once this is complete, the mature mRNA can then exit the nucleus through the
nuclear pores to enter the cytoplasm.
In the cytoplasm, the mRNA can bind to a specialized organelle called the
ribosome. The sequence of nucleotides in the mRNA is converted into a polypeptide, which we can
see exiting the ribosome. This can go on to fold into a protein that corresponds to the original gene that was
transcribed.
Therefore, going back to our question, the option that correctly identifies what
happens to a strand of mRNA once it’s formed is given by answer choice (D). It leaves the nucleus through the nuclear pores.