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Predict and interpret patterns of inheritance Genetics Unit
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What is heredity? The passing on of characteristics (traits) from parents to offspring Genetics is the study of heredity
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Probability The likelihood that a particular event will occur. The principle of probability can be used to predict the outcome of genetic crosses.
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Rule of Unit Factors Each organism has two alleles for each trait Alleles - different forms of the same gene Genes - located on chromosomes, they control how an organism develops
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Dominant Alleles The trait that is always expressed if at least one allele is present in the offspring. Represented by a capital Letter Recessive Alleles The trait that is only expressed if an organism has both recessive alleles. Represented by a lower case letter.
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Punnett Square Punnett squares can be used to predict and compare the genetic variations that will result from a cross. Homozygous – Organisms that have two identical alleles for a particular trait. (TT or tt) Heterozygous – Organisms that have two different alleles for the same trait. (Tt) Phenotype – physical characteristics (blue eyes) Genotype – genetic makeup (alleles Tt, TT, tt)
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Monohybrid Cross - crossing parents who differ in only one trait (AA with aa)
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Punnett Square (Monohybrid)
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Dihybrid Cross - crossing parents who differ in two traits (AAEE with aaee)
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Punnett Squares (Dihybrid)
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Incomplete Dominance One allele is not completely dominant over the other allele. The heterozygous phenotype is somewhere between the dominant and the recessive trait.
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Both alleles are dominant and show up in the phenotype. Codominance
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A gene with more than two alleles. This only means that there are more than two forms of the trait. Multiple Alleles
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Traits controlled with two or more genes. Polygenic Traits
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Characteristics of any organism are a result of an interaction between genes and environment. Genes provide a blueprint, but environmental factors can alter the finished product.
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