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Chapter 9 Section 1 Review

Chapter 9 Section 1 Review. . 1. Describe what a true-breeding plant is. Plants that are true-breeding for a trait always produce offspring with that trait when they self-pollinate. purebreds.

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Chapter 9 Section 1 Review

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  1. Chapter 9 Section 1 Review .

  2. 1. Describe what a true-breeding plant is. • Plants that are true-breeding for a trait always produce offspring with that trait when they self-pollinate purebreds

  3. 2. Outline how Mendel produced plants that had genes for both contrasting traits of a characteristic. • He first produced true-breeding plants. • Then he crossed the true-breeds. • He allowed the offspring (F1) to self-pollinate and this produced contrasting traits in the F2 generation.

  4. 3. Define the terms dominate and recessive. • Dominant- the factor that controls the characteristic; masks or dominates the recessive.

  5. 5. Differentiate genes from alleles. • Gene- a segment of DNA on a chromosome Allele- alternative form of a gene

  6. 6. How did Mendel’s F1 generation plants differ from his F2 generation plants? • F1- all offspring exhibited the dominant allele • F2-was a result of allowing F1 offspring to self-pollinate; a 3:1 ratio

  7. 7. Many inherited disorders of humans appear in children of parents who do not have the disorder. How can you explain this? • The disease is recessive and each parent is a carrier; heterozygous

  8. 8. During meiosis, what allows genes located on the same chromosome to separate independently of one another? • Crossing-over

  9. Section 2: Genetic Crosses • Genotype- the alleles that the organism inherits from its parents (PP, Pp or pp) • Phenotype- an organism’s appearance

  10. Homozygous- when both alleles of a pair are the same; BB or bb (dominant or recessive) • Heterozygous- when both alleles are different; Bb

  11. Probability • The likelihood that a specific event will occur • Probability= # of times an event is expected to happen # of times an event could happen

  12. Mendel studied statistics in math

  13. Monohybrid cross • A cross that looks at just one trait; shows 4 offspring

  14. Dihybrid cross • Tracks two traits at the same time; 16 offspring

  15. TestCross • A cross performed between an unknown genotype and a homozygous recessive individual Helps to determine to genotype of an individual whose phenotype expresses the dominant trait

  16. Example… BB or Bb? (Black) • ½ would be expected to be brown if the genotype of your black guinea pig was Bb. None would be brown if the genotype was BB. B b Bb bb b b Bb bb

  17. Complete dominance • All of the traits Mendel studied exhibited complete dominance. Every phenotype was either dominant or recessive. There was no “in-between” • In complete dominance the heterozygous and homozygous dominant genotypes look the same. • (BB or Bb)

  18. Example: • There were no medium sized plants in Mendel’s studies

  19. Incomplete dominance • Most traits work like this… • This is when the phenotype of the heterzygote looks different than either parent

  20. Codominance • Each alleles for a gene is expressed in heterozygous offspring; neither allele is dominant or recessive • Written with 2 caps; AB

  21. Examples…

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