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8/1/13 GENETICS Homologous Chromosomes Two genes for one trait One from male One from female Identical genes (homozygous) or Different genes (heterozygous) Called alleles Genetics Genotype genetic makeup of the trait. FF, Ff, ff YY, Yy, yy Phenotype outward appearance of the trait. Ear lobes (free or attached) Seed color (yellow or green) 1 8/1/13 Genetics Dominant/recessive Homozygous dominant YY (Yellow seeds) Heterozygous Homozygous recessive Yy (Yellow seeds) yy (Green seeds) Genetics Incomplete dominance (blending) Red flowers AA Pink flowers Aa White flowers aa Genetics Polygenic inheritance More than one gene is involved in the trait Human skin color Corn seed color at least 4 genes 2 8/1/13 Genetics - Polygenic Genetics - Polygenic Y - timing of chlorophyll elimination (Y - early; y - normal) R - color of carotenoids (R - red; r - yellow) C - regulation of carotenoid deposition (C - normal; c1, c2 - lowered concentration) *This leads to a few possible genotypes producing interesting phenotypes: * Y- rr c1c2 - pale yellow * Y- rr Cc2 - darker yellow * yy rr CC - green * Y- R- CC - red * yy Rr CC - purple * Y- Rr Cc2 - pale yellow ------------------------------------------------------------------------ Molecular Genetics DNA genetic material Sequence of four nucleotides Adenine, cytosine, guanine, and thymine Transcription Translation DNA codes for messenger RNA RNA sequence to sequence of amino acids in proteins 3 8/1/13 Protein Synthesis Evolution - Natural Selection Many variations within a population Mutations and meiosis More individuals are produced then survive and reproduce. Those individual with favorable variations are selected by the environment and reproduce. Evolution - Natural Selection Over a long period of time the species will fit the environment. End result is many species fitting into many specific environments. 4 8/1/13 Natural selection Types Directional Stabilizing Disruptive Natural selection - Types Directional Stabilizing Disruptive (diversifying) Natural selection 5 8/1/13 Artificial Selection 1. Selective breeding 2. Hybrids 3. Polyploidy Recombinant DNA 4. Genetically modified foods Artificial Selection - Selective Breeding Throughout human history Teosinte to corn Pistachios to grow in California Rapeseed - Canola oil Marijuana Low erucic acid and glucosinolates (1974) Bushier plants and more psychoactive THC Artificial Selection 1. Selective breeding 2. Hybrids 3. Polyploidy 4. Recombinant DNA Genetically modified foods 6 8/1/13 Artificial Selection - Hybrids Hybridization within a species Out-crossing leads to genetic variability Inbreeding or self-fertilization leads to less genetic variability or identical homozygous individuals Produce a more standard or uniform plants and seeds. The offspring of two inbred plant parents Produce hybrids that more often have larger seeds or fruit. This is hybrid vigor. Artificial Selection - Hybrids Artificial Selection - Hybrids Hybrids can also occur between two species Natural hybridization Black sage + White sage = Hybrid Artificial Selection Grapefruit + Tangerine = Tangelo Wheat + Rye = Triticale Plum + apricot = pluot 7 8/1/13 Animal Hybrids - Mule • Sterile • Donkey 62 chromosomes (31 pairs) • Horse 64 (32 pairs) • Mule and hinny each have 63 chromosomes • Many pairs are unevenly matched • The donkey and horse chromosomes are almost completely unable to pair up at meiosis to produce viable sperm and eggs Meiosis Reduction division 2N (diploid) to 1N (haploid) 1N Increases genetic variation 2N 1N Artificial Selection 1. Selective breeding 2. Hybrids 3. Polyploidy 4. Recombinant DNA Genetically modified foods 8 8/1/13 Artificial Selection - Polyploidy Increase in chromosome number tetraploid, hexaploid or octaploid. Mechanism of polyploidy is non-disjunction. Same number or different number of chromosomes. Non-disjunction cause of polyploidy Tetraploid Artificial Selection - Polyploidy Larger plants, fruit, and or seeds Occurs naturally by accident Occurs through genetic selection or manipulation Drug colchicine Cotton, Easter lily - tetraploid Wheat - hexaploid Strawberry - octaploid 9 8/1/13 Non-disjunction in animals Trisomy Down’s syndrome Monosomy Turner’s syndrome Artificial Selection 1. Selective breeding 2. Hybrids 3. Polyploidy Recombinant DNA 4. Genetically modified foods Artificial Selection - Recombinant DNA Addition of other plant, animal or bacterial genes (DNA segment) into genome of another plant species. The use of plasmids or small circular sections of DNA. Incorporate desired gene into plasmid DNA Infect into bacteria DNA. Bacteria infect the plant with the plasmid and hopefully insert plasmid and desired DNA into plant genome. 10 8/1/13 GMF 2006 7 million farmers in 18 countries United States Don’t label foods as GMO Brazil Argentina India Canada China Paraguay South Africa Genetically Modified Foods Herbicide (Roundup Ready) resistant 90% Soybeans, 2/3 cotton, ¼ corn, and rapeseed Insect resistance (Bacillus thuringiensis Bt) 11 8/1/13 GMF - Benefits Enhanced taste and quality of food Vitamin A in rice Tomatoes with higher lycopene content Reduced maturation time Increased nutrients and yields Stress tolerance Improved resistance to disease, pests, and herbicides Tolerance to cold Tomatoes and strawberries Production of vaccines GMF - Controversies Potential human health impacts, including allergens, transfer of antibiotic resistance markers, unknown effects Unintended transfer of transgenes through crosspollination Unknown effects on other organisms Corn pollen toxic to Monarch butterflies Loss of flora and fauna biodiversity Domination of world food production by a few companies Tampering with nature by mixing genes among species 12