Cellular Control

• Epigenetic modifications regulate gene expression during cellular differentiation and development.
• Phosphorylation and acetylation causes the proteins to become more compact and more stable and causes the formation of heterochromatin
• methylation causes formation of euchromatin, which is more accessible to transcription factors
• Gene I in the lac operon is expressed constitutively, which means it is constantly expressed. It codes for a repressor protein which binds to the operator and prevents transcription. When lactose is present, the repressor protein is removed and the operator is no longer bound, allowing transcription to occur as RNA polymerase can then bind to the promoter.
• Gene Z in the lac operon codes for Beta Galactosidease and Gene Y codes for lactose permease
• Using Drosophila to perform an investigation about body plan development is ideal as they have short life span and fast reproduction (so changes over generations can be quickly observed), they are small and easy to store, less ethical concerns keeping them, their genome os well known
• Hox genes display collinearity, which means their order corresponds to the spacial and temporal development of the various body parts in an organism
• Hox genes can determine the polarity of an embryo. They determine the identity of the embryonic body regions along the anterior-posterior axis
• Homeobox genes are found in plants, animals and fungi whereas Hox genes are a subset of homeobox genes that are only found in animals
• Hox genes form Hox clusters, which are regions of the genome that are highly conserved. They also code for transcription factors known as the homeodomain and control expression of genes relating to body plan development. Each sequence contains 180 base pairs and codes for 60 amino acids. The homeodomain folds into the shape helix turn helix. It recognises the sequence TAAT on the enhancer region of the gene to be transcribed
• The three types of point mutation are silent, missence and non-sense. Silent means the mutated codon still codes for the same amino acid. Missence means the mutated codon codes for a different amino acid. Non-sense means the mutated codon codes for a stop codon.
• The two types of frameshift mutations are insertion and deletion. This mutation affects all of the codons down stream of the mutation and can lead to the formation of a truncated protein.
• During transcription, RNA polymerase moves along the template strand from 3' to 5' and forms a strand of mRNA running from 5' to 3'
• The antisense strand acts as the template strand and the sense strand acts as the coding strand. mRNA is formed using the template strand
• Post-transcriptional modifications include splicing of pre mRNA to form mature mRNA. Introns are cut out of the strand. Alternative splicing can take place so different combinations of exons can be used to form different proteins.
• cAMP is involved with post translation genetic control and can be used to activate proteins e.g. enzymes in cytoplasm