The following links offer some useful revision on Cell Structure to support your learning:
At Higher, you will need to know the following:
- Phenotype is determined by the proteins produced as the result of gene expression.
- Only a fraction of the genes in a cell are expressed.
- Gene expression is influenced by intra- and extra-cellular environmental factors
- Gene expression is controlled by the regulation of both transcription and translation.
- Structure and functions of RNA. RNA is single stranded, contains uracil instead of thymine and ribose instead of deoxyribose sugar.
- Messenger RNA (mRNA) carries a copy of the DNA code from the nucleus to the ribosome.
- Ribosomal RNA (rRNA) and proteins form the ribosome.
- Each transfer RNA (tRNA) carries a specific amino acid.
- Transcription of DNA into primary and mature RNA transcripts in the nucleus. This should include the role of RNA polymerase and complementary base pairing.
- mRNA is transcribed from DNA in the nucleus and translated into proteins by ribosomes in the cytoplasm. RNA polymerase moves along DNA unwinding and unzipping the double helix and synthesising a primary transcript of RNA by complementary base pairing. Genes have introns (non -coding regions of genes) and exons (coding regions of genes).
- The introns of the primary transcript of mRNA are non -coding and are removed in RNA splicing. The exons are coding regions and are joined together to form mature transcript. This process is called RNA splicing.
- Translation of mRNA into a polypeptide by tRNA at the ribosome. tRNA folds due to base pairing to form a triplet anticodon site and an attachment site for a specific amino acid
- Triplet codons on mRNA and anticodons translate the genetic code into a sequence of amino acids.
- Start and stop codons exist.
- Codon recognition of incoming tRNA, peptide bond formation and exit of tRNA from the ribosome as polypeptide is formed.
- Different proteins can be expressed from one gene as a result of alternative RNA splicing and post -translational modification.
- Different mRNA molecules are produced from the same primary transcript depending on which RNA segments are treated as exons and introns.
- Post -translation protein structure modification by cutting and combining polypeptide chains or by adding phosphate or carbohydrate groups to the protein.
