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INTRO TO GENETICS History Native Americans Domestication of wolf Developing corn & potatoes Aristotle Blood contains hereditary material “blood relatives”, “bloodline” “Blending Hypothesis” “Renaissance” (17th century) Parents traits (characteristics) are blended together in their offspring. Example: A tall mom and short dad will produced a child with medium height. Gregor Mendel Austrian monk (19th century) Other interests: Math, biology, physics Pea breeder “Father of Genetics" Peas: the perfect specimen Produce many offspring Short life cycle Easy to control the experiment Easily identified traits: Pea Biology Plant reproduction Pollen produced in stamen Carries sperm Egg contained in the pistil Holds the egg Pollen grain lands on pistil and produces a pollen tube. Sperm travels through tube. Sperm fertilizes the egg. Method of Self-fertilization Selective Breeding Parent Generation “Purebred” (self-fertilized) parents. F1 Generation “Hybrid” offspring“ All possess traits of one parent. F2 Generation Self-fertilized 3 of 4 with one parent trait. 1 of 4 with the other parent trait Mendel’s Hypothesis Each trait is controlled by a gene. Two or more alternative forms of a gene (ex. tall & short). These forms are called “alleles”. Each trait is the result of a pair of alleles being expressed. Each allele being located on different copies of a chromosome Example: Tall / tall; tall / short; short / short Law of Dominance One allele is dominant over the other Tall (T) is the dominant allele Short (t) is the recessive allele Pure dominant (T / T) and hybrid (T / t) will produce tall plants. Only pure recessive (t / t) will produce short plants. Terminology Genotype – combination of alleles Ex.: “T / t” Phenotype – expression of the allele pair. Ex.: “tall” Homozygous – allele of pair is the same Ex.: “t / t” Heterozygous – alleles of pair are different Ex.: “T / t” Law of Segregation Pairs of alleles separate when “gametes” (sex cells) are produced. Example: Hybrids (T / t) will have gametes with either “T” allele or “t” allele. Alleles will pair up again during fertilization. Ex.: “T” from sperm and “t” from egg will produce a “T / t” allele pair. Punnett Square Predicts result between parents. Monohybrid Cross Law of Independent Assortment Genes for different traits are inherited independently of each other Ex.: Alleles for height will not influence the alleles for seed color or seed shape Dihybrid Cross Two genes, each that are heterozygous.
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