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Transcript
Genes & Genetic Engineering Contents Genetic Code Cell Cycle Sexual Reproduction Applications of Gene Technology Genetic Code Sequence of bases on DNA These code the sequence of amino acids in proteins 1st 2 are most important 20 amino acids 4 bases grouped into 3s 64 combinations Codon Genetic code Universal Code: The code is used between species. Each base sequence codes for the same amino acid Many base sequences can code for the same amino acid “Stop” (UAG, UGA, UUA) does not code for an amino acid Genetic Code Amino Acid mRNA Codons Cell Cycle Cell cycle varies from hours to years - Bacterial cells divide every 30 minutes - Liver cells divide every 2 hours Four cycles: - Gap 1, Synthesis, Gap 2, Mitosis Mitosis has four phases: - prophase, metaphase, anaphase, telophase Mitosis results in 2 daughter cells, genetically identical to each other. Used for growth and asexual reproduction Cell Cycle Cell grows & produces Gap 2 proteins for cell division. Determines if cell can undergo mitosis. mitosis Gap 1 Interphase: Gap 1 + synthesis + Gap 2 DNA synthesis DNA synthesis (replication). Cell size increases RNA and synthesise proteins produced. Preparations for DNA synthesis. Cell stops dividing. Gap 0 Temporary or permanent. Meiosis (Sexual Reproduction) Mitosis produces 2 genetically identical daughter cells Meiosis occurs directly afterwards with 2 further divisions Meiosis therefore results in 4 daughter cells with: - half the number of chromosomes (diploid 2n haploid n) - new combinations of genes so no two will be identical Meiosis (Sexual Reproduction) Advantages: - genetic variation and wide diversity of life - allows species to adapt and evolve Disadvantages: - complex - slower than mitosis Applications of Gene Technology 3 main applications to date: - Gene Products: using genetically modified (GM) organisms (usually microbes) to produce chemicals for medical or industrial applications - New Phenotypes: using gene technology to alter the characteristics of organisms such as crops - Gene Therapy: using gene technology on humans to treat diseases Gene Products GM Product Application Host Organism AAT Cystic fibrosis Sheep Anti-thrombin Anti-blood clotting (surgery) Goats BST Increase cows’ milk yields Bacteria Factor VIII Human blood clotting (haemophiliacs) Bacteria HGH Human growth hormone Bacteria Penicillin Antibiotic to kill bacteria Fungi Vaccines Hep B antigen Yeast Rennin Manufacture of cheese Bacteria New Phenotypes These include: - Fast-growing sheep & fish - Crops resistant to insects, herbicides & viruses - Long life tomatoes & some fruit - Crop improvement & nitrogen-fixing crops - Cattle resistant to mastisis ( higher yield of milk) - Sheep resistant to ticks ( may not need sheep dip) Gene Therapy Altering the genotype of a tissue or organ In early stages but treatments hope to include: - GM white blood cells that produce proteins that kill cancer cells - targeting genes at cancer cells to kill them or revert them back to normal cells - white blood cells that would not reproduce if infected with HIV - germ-line modification (only present in animals) which is currently illegal - at present, only somatic cell therapy is legal which alters only specific cells in the body Summary Genetic code: Sequence of 20 amino acids & 4 bases, grouped into 3s. It is a universal code (all species) Cell cycle: Interphase = Gap 1 + synthesis + Gap 2 Sexual reproduction, meiosis produces non-identical daughter cells and is vital for organisms to evolve Applications of gene technology include gene products (e.g. penicillin), new phenotypes (long life tomatoes) and gene therapy (in early stages)