Download Genetics

8/1/13
GENETICS
Homologous Chromosomes
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Two genes for one trait
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One from male
One from female
Identical genes
(homozygous) or
Different genes
(heterozygous)
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Called alleles
Genetics
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Genotype genetic makeup of the trait.
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FF, Ff, ff
YY, Yy, yy
Phenotype outward appearance of the trait.
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Ear lobes (free or attached)
Seed color (yellow or green)
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Genetics
Dominant/recessive
  Homozygous dominant
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YY (Yellow seeds)
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Heterozygous
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Homozygous recessive
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Yy (Yellow seeds)
yy (Green seeds)
Genetics
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Incomplete dominance (blending)
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Red flowers AA
Pink flowers Aa
White flowers aa
Genetics
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Polygenic inheritance
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More than one gene is involved in the trait
Human skin color
Corn seed color at least 4 genes
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Genetics - Polygenic
Genetics - Polygenic
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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:
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Y- rr c1c2 - pale yellow
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Y- rr Cc2 - darker yellow
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yy rr CC - green
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Y- R- CC - red
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yy Rr CC - purple
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Y- Rr Cc2 - pale yellow
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Molecular Genetics
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DNA genetic material
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Sequence of four nucleotides
Adenine, cytosine, guanine, and thymine
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Transcription
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Translation
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DNA codes for messenger RNA
RNA sequence to sequence of amino acids
in proteins
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Protein Synthesis
Evolution - Natural Selection
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Many variations within a population
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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
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Over a long period of time the species will fit
the environment.
End result is many species fitting into many
specific environments.
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Natural selection
Types
  Directional
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Stabilizing
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Disruptive
Natural selection - Types
Directional
Stabilizing
Disruptive
(diversifying)
Natural selection
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Artificial Selection
1. 
Selective breeding
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Hybrids
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Polyploidy
Recombinant DNA
4. 
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Genetically modified foods
Artificial Selection - Selective Breeding
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Throughout human history
Teosinte to corn
Pistachios to grow in California
Rapeseed - Canola oil
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Marijuana
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Low erucic acid and glucosinolates (1974)
Bushier plants and more psychoactive THC
Artificial Selection
1. 
Selective breeding
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Hybrids
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Polyploidy
4. 
Recombinant DNA
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Genetically modified foods
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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
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Produce a more standard or uniform plants and
seeds.
The offspring of two inbred plant parents
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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
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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
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Reduction
division
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2N (diploid) to
1N (haploid)
1N
Increases genetic
variation
2N
1N
Artificial Selection
1. 
Selective breeding
2. 
Hybrids
3. 
Polyploidy
4. 
Recombinant DNA
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Genetically modified foods
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Artificial Selection - Polyploidy
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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
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Larger plants, fruit, and or seeds
Occurs naturally by accident
Occurs through genetic selection or
manipulation
Drug colchicine
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Cotton, Easter lily - tetraploid
Wheat - hexaploid
Strawberry - octaploid
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Non-disjunction in animals
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Trisomy
Down’s
syndrome
Monosomy
Turner’s
syndrome
Artificial Selection
1. 
Selective breeding
2. 
Hybrids
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Polyploidy
Recombinant DNA
4. 
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Genetically modified foods
Artificial Selection - Recombinant DNA
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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.
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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.
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GMF 2006
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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
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Herbicide (Roundup Ready) resistant
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90% Soybeans, 2/3 cotton, ¼ corn, and rapeseed
Insect resistance (Bacillus thuringiensis Bt)
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GMF - Benefits
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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
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Potential human health impacts, including allergens,
transfer of antibiotic resistance markers, unknown
effects
Unintended transfer of transgenes through crosspollination
Unknown effects on other organisms
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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
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