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Published byCody Bridges Modified over 9 years ago
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11.3 Other Patterns of Inheritance
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Beyond Simple Dominance Not all genes show simple patterns simple patterns of inheritance Most genes have more than two alleles or are controlled by more than one gene
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Incomplete Dominance Some alleles are neither dominant nor recessive In complete dominance, neither allele is dominant The heterozygous phenotype lies somewhere between the two homozygous phenotypes The heterozygous genotype yields a mixed phenotype
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Codominance Phenotypes produced by both alleles are clearly expressed Many human genes are codominant, including blood types The heterozygous genotype yields BOTH phenotypes
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Multiple Alleles Many genes exist in several different forms and are therefore said to have multiples alleles A genes that have more than two alleles is said to have multiple alleles An individual has only two copies of each gene, but more than two exist in a population EX: Rabbit fur color, human blood types
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Polygenic Traits Many traits are produced by the interaction of several genes Traits controlled by two or more genes are said to be polygenic (many genes) traits Often show a wide range of phenotypes Four+ genes control human skin color
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Genes and the Environment Environmental conditions can effect gene expression and influence genetically determined traits Phenotype is determined by genes + environment
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Genes and the Environment Examples: Gene or Environment? – A blue eyed girl is born to two blue eyed parents – A pair of twins is separated at birth. They grow up in different countries and speak different languages. – A kitten is born with six toes.
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