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What does RNA stand for?
State three differences between DNA and RNA
- DNA contains deoxyribose sugar but RNA contains ribose sugar
- DNA contains a double strand (double helix) but RNA contains a single strand
- DNA contains thymine but RNA contains uracil
What are the two types of RNA?
- mRNA - messenger RNA
- tRNA - transfer RNA
What are the two stages of protein synthesis?
- Transcription - involving mRNA
- Translation - involving tRNA
Describe protein synthesis
- In the nucleus DNA is unzipped by an enzyme
- One section of one strand of DNA is exposed and a molecule of mRNA is transcribed using free nucleotides present in the nucleus. Complementary base pairing (G-C, C-G, A-U, T-A) determines the sequence of the bases on the mRNA molecule. When the mRNA molecule is complete, it leaves the nucleus through the nuclear pores and enters the cytoplasm
- In the cytoplasm there are tRNA molecules which bear a triplet (anticodon) of bases corrosponding to a particular amino acid. Each tRNA molecule picks up the appropriate amino acid from the cytoplasm.
- The mRNA molecule becomes attached to a ribosome. Its triplet code is read and a tRNA anticodon links with each complementary codon of bases on the mRNA molecule.
- Peptide bonds form between adjacent amino acids.
- The completed protein is then released into the cytoplasm