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Chapter 6 Mendelian Genetics
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Genetics – the scientific study of heredity Gregor Mendel is said to be the father of genetics. Mendel used pea plants to study the inheritance of traits.
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True-breeding – plants that produce offspring identical to themselves. Parents that have different traits will produce hybrids. Hybrids are offspring of parents with different traits.
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Mendel’s Pea Traits Traits – Traits are specific characteristics (like blue eyes or 5 fingers)
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Genes are factors that are passed from one generation to the next. (From parents to offspring) Alleles are different forms of a gene (like purple or white flowers).
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Law of Dominance This principle states that some alleles are dominant and others are recessive. The dominant allele is represented by an uppercase letter. P – purple flower The recessive allele is represented by a lowercase letter. p – white flower
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Dominant – Trait that will hide or mask the recessive trait Recessive – Trait that will show only when found with another recessive allele Genotype – what the alleles are Phenotype – observable characteristics
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P Generation is the first parental generation. F 1 is called the first filial generation or the first offspring when the P generation is crossed. F 2 is called the second filial generation or the offspring from crossing the F 1 generation.
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Mendel’s Law of Segregation Mendel wanted to know what happened to the recessive alleles. He allowed for F 1 plants to self pollinate and this resulted in some F 2 plants showing the recessive trait. The two alleles separate when organisms produce gametes, or sex cells. Each gamete carries a single copy of each gene.
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Homozygous - Organisms that have two identical alleles for a particular trait Ex. TT or tt Heterozygous - Organisms that have two different alleles for a particular trait (Hybrids) Ex. Tt Punnett squares show: Possible genotypes The alleles in the gametes of parents All possible results of a genetic cross
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Probability Probability is the likelihood that a specific event will occur. Flip a coin 100 times; record the number of times it is heads _____ and tails_____ Principles of probability can be used to predict the traits of offspring produced by genetic crosses
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Mendel’s Law of Independent Assortment Genes for different traits can segregate (on separate chromosomes) independently during the formation of gametes. Example: Seed shape doesn’t determine seed color.
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