(3) Gene Expression Gene Expression (A) What is Gene Expression? (E) Splicing and post-translational modification (B) Structure and Functions of RNA (D) Translation (C) Transcription

Gene Expression (a) State what is meant by ‘phenotype’ State what ‘phenotype’ is determined by Name 2 factors that influence gene expression Name the 2 stages involved in Protein Synthesis State how gene expression is controlled

What is Gene Expression? Humans like all organisms are ‘built’ from proteins. So the proteins each person produces determines their phenotype (physical appearance). The instructions or code to make these proteins are found in short sections of DNA called genes. Humans contain 25,000 genes but only a fraction of the genes in a cell are expressed (only a fraction of genes are copied and used to make proteins)

Influencing Gene Expression Signals from the outside world can work through the genome to change a cell's gene expression. Click on the link below to access the animation. In the activity, you act as the signal. As you turn the control knob, epigenetic tags come and go to change the shape of the gene. http://learn.genetics.utah.edu/content/e pigenetics/control/ DNA is coiled around histones. Tightly coiled DNA is inaccessible to the gene reading machinery called RNA polymerase Methyl molecules bind to DNA and block access to genes. Acetyl molecules bind to histones and improve access to genes.

Green Fluorescent Protein

Influencing Gene Expression Not all genes are expressed. This is because gene expression is influenced by: Intra-cellular environmental factors (a variety of molecules found inside the cell) Extra-cellular environmental factors. Regulation of gene transcription is known as epigenetics and is the mechanism by which the activity of any gene is ‘turned’ up or down. To live, cells must be able to respond and adapt to changes in their environment. Regulation of the two main steps of protein production is critical to this adaptability.

Controlling Gene Expression There are 2 main steps in Protein Synthesis: Step 1 – Transcription The DNA code is copied into a messenger molecule known as mRNA Step 2 - Translation The mRNA code is used to assemble amino acids into the correct order to make the protein inside structures known as ribosomes Gene expression is controlled by the regulation of both transcription and translation

Gene Expression (a) State what is meant by ‘phenotype’ State what ‘phenotype’ is determined by Name 2 factors that influence gene expression Name the 2 stages involved in Protein Synthesis State how gene expression is controlled