1. Genes Activity  Aims:  Must be able to outline the various functions of genes.  Should be able to outline how genes can be activated and when and where.  Could be able to explain the purpose of variations in gene activity.

2. Various Functions  Genes vary due the functions they ultimately perform.  Genes can be:  STRUCTURAL GENES:  REGULATOR GENES:  HOMEOTIC GENES:

3. Structural Genes  Produce proteins that become part of the structure and functioning of a cell or oganism.

4. Regulatory Genes  Produce proteins that control the action of other genes.  Determine whether genes are active or not and how fast they produce their products.  Genes switch other genes ‘on’ and ‘off’ by producing proteins that work in one of two ways: DNA bin-binding proteins binds to regions in DNA near genes and directly switch them ‘on’ or ‘off’. Proteins bind to cell membrane and trigger a series of intracellular reactions that switch gene ‘on’ or ‘off’.

5. Homeotic Genes (master genes)  Control embryonic development in insects and vertebrates.  Control the actions of hundreds of other genes.  Important in the building of various parts of the organism at certain times in development.  Homeotic genes are known as HOX genes in mammals.  HOX genes are arranged in 4 clusters: HOXA, 11 genes, chromosome 7 HOXB, 10 genes, chromosome 17 HOXC, 9 genes, chromosome 12 HOXD, 9 genes, chromosome 2  Mutations in HOX genes can result in profound differences in phenotypes.

6. When are Genes Active  Genes vary in their time of activity.  Some are active for only days or weeks or at particular ages: Genes for embryonic blood. Genes for Huntington’s disease.  Some are active for the entire life: Those responsible for enzyme production.

7. Where are Genes Active  Some genes are only active in cells of certain tissues: Genes for beta haemoglobin (HBB) only active in cells of bone marrow destined to be RBC. Dystrophin protein gene (DMD) only active in skeletal muscle tissue. Gene for the production of growth hormone (GH) only active in the pituitary gland.  Some genes are active in all tissues: Genes for enzymes involved in cellular respiration.

8. Identifying Active Genes  A ‘switched on’ gene is one that is transcribing mRNA, a ‘switched off’ gene is not producing mRNA.  MICROARRAYS is a new technology that allows Scientists to study a large number of genes simultaneously and: Identify active and inactive genes at a given time. Compare gene expression in different cell types. Compare genes in same cell types under different conditions.  Diagram p408.  Notes on future applications of Mircoarray technology.

9. Activity  Notes on ‘Switching Off Genes’ p409-411.  Biozone p197 – 206 – Recap on DNA replication and Transcription and Translation.