Genes & Genetic Engineering

Contents Genetic Code Genetic Code Cell Cycle Cell Cycle Sexual Reproduction Sexual Reproduction Applications of Gene Technology Applications of Gene Technology

Genetic Code Sequence of bases on DNA Sequence of bases on DNA These code the sequence of amino acids in proteins These code the sequence of amino acids in proteins 20 amino acids 20 amino acids 4 bases 4 bases Universal Code: The code is used between species. Each base sequence codes for the same amino acid 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 Many base sequences can code for the same amino acid “Stop” (UAG, UGA, UUA) does not code for an amino acid “Stop” (UAG, UGA, UUA) does not code for an amino acid grouped into 3s  64 combinations Codon Genetic code 1 st 2 are most important

Genetic Code

Amino Acid mRNA Codons

Cell Cycle Cell cycle varies from hours to years Cell cycle varies from hours to years - Bacterial cells divide every 30 minutes - Liver cells divide every 2 hours Four cycles: Four cycles: - Gap 1, Synthesis, Gap 2, Mitosis Mitosis has four phases: 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 Mitosis results in 2 daughter cells, genetically identical to each other. Used for growth and asexual reproduction

Cell Cycle mitosis Gap 1 Gap 0 DNA synthesis Gap 2 Cell size increases RNA and synthesise proteins produced. Preparations for DNA synthesis. Cell stops dividing. Temporary or permanent. DNA synthesis (replication). Cell grows & produces proteins for cell division. Determines if cell can undergo mitosis. Interphase: Gap 1 + synthesis + Gap 2

Meiosis (Sexual Reproduction) Mitosis produces 2 genetically identical daughter cells Mitosis produces 2 genetically identical daughter cells Meiosis occurs directly afterwards with 2 further divisions Meiosis occurs directly afterwards with 2 further divisions Meiosis therefore results in 4 daughter cells with: 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: Advantages: - genetic variation and wide diversity of life - allows species to adapt and evolve Disadvantages: Disadvantages: - complex - slower than mitosis

Applications of Gene Technology 3 main applications to date: 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 Bacteria Manufacture of cheese Rennin Yeast Hep B antigen Vaccines Fungi Antibiotic to kill bacteria Penicillin Bacteria Human growth hormone HGH Bacteria Human blood clotting (haemophiliacs) Factor VIII Bacteria Increase cows’ milk yields BST Goats Anti-blood clotting (surgery) Anti-thrombin Sheep Cystic fibrosis AAT Host Organism Application GM Product

New Phenotypes These include: 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 Altering the genotype of a tissue or organ In early stages but treatments hope to include: 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) 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 Cell cycle: Interphase = Gap 1 + synthesis + Gap 2 Sexual reproduction, meiosis produces non-identical daughter cells and is vital for organisms to evolve 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) Applications of gene technology include gene products (e.g. penicillin), new phenotypes (long life tomatoes) and gene therapy (in early stages)