Types of RNA
Biology: IB Diploma Higher Level, topic 1.3.2
Types of RNA
RNA is a single-stranded nucleic acid molecule that is made from the same bases as DNA except for uracil (U) which is used instead of thymine (T). There are different types of RNA:
mRNA
- Messenger RNA (mRNA) is transcribed from DNA in the nucleus to produce a single-stranded RNA.
- The mRNA strand is complementary to the DNA base sequence.
- mRNA travels from the nucleus to the ribosomes in the cytoplasm.
- Ribosomes are proteins that translate mRNA into amino acids and synthesize the polypeptide.
tRNA
- Transfer RNA (tRNA) forms a clover-like shape and is vital for translation.
- tRNA reads the mRNA codons and brings the corresponding amino acid into the ribosomes.
Accuracy of tRNA
- It is important that the correct amino acid is brought to the ribosomes by tRNA so that the protein is assembled correctly.
- Each tRNA molecule has an anticodon which is complementary to a specific codon on mRNA.
- The amino acid that corresponds to a specific anticodon binds to a specific attachment site on the tRNA molecule.
DNA → amino acid
- There are many processes in producing an amino acid from the original DNA sequence.
- If the original DNA sequence has the codon GCC, the codon in each step is:
- DNA codon: GCC.
- mRNA complementary codon: CGG.
- tRNA anticodon: GCC.
- Amino acid: Arginine.
rRNA
- Ribosomal RNA (rRNA) is a key component of ribosomes.
- rRNA is hence vital for protein synthesis to occur.
Test yourself on Types of RNA
What feature of tRNA molecules ensures each tRNA binds to the correct codon?
Which of the following statements about RNA are true?
If the DNA codon is CAG, what will the mRNA complementary codon be?