Messenger RNA (mRNA) carries the genetic information of a gene from DNA, which stays in the nucleus, to the ribosomes in the cytoplasm where the polypeptide is made.Structure:
• a single, linear polynucleotide strand (it does not fold into a fixed shape)
• nucleotides contain ribose and the bases A, U, C and G
• its base sequence is complementary to the template strand of the gene, so it is a copy of the other (coding) strand with U in place of T
• its bases are read in triplets called codons, each coding for one amino acidmRNA is made in the nucleus by transcription. In eukaryotes the first copy (pre-mRNA) is modified by splicing, which removes non-coding sections (introns) and joins the coding sections (exons). The mRNA then leaves the nucleus through a nuclear pore, which DNA is too large to pass through.mRNA is short-lived. It is broken down after it has been translated a number of times, which lets the cell control how much of a protein it makes.Worked example: a DNA template strand reads TAC GGA. Pairing A with U, T with A, C with G and G with C gives the mRNA AUG CCU.An mRNA of 90 codons ending in one stop codon codes for 89 amino acids, as the stop codon codes for none.
• a single, linear polynucleotide strand (it does not fold into a fixed shape)
• nucleotides contain ribose and the bases A, U, C and G
• its base sequence is complementary to the template strand of the gene, so it is a copy of the other (coding) strand with U in place of T
• its bases are read in triplets called codons, each coding for one amino acidmRNA is made in the nucleus by transcription. In eukaryotes the first copy (pre-mRNA) is modified by splicing, which removes non-coding sections (introns) and joins the coding sections (exons). The mRNA then leaves the nucleus through a nuclear pore, which DNA is too large to pass through.mRNA is short-lived. It is broken down after it has been translated a number of times, which lets the cell control how much of a protein it makes.Worked example: a DNA template strand reads TAC GGA. Pairing A with U, T with A, C with G and G with C gives the mRNA AUG CCU.An mRNA of 90 codons ending in one stop codon codes for 89 amino acids, as the stop codon codes for none.