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Chapter 9 – Fundamentals of Genetics

Chapter 9 – Fundamentals of Genetics. Gregor Mendel. Austrian monk Experimented with pea plants. Studied heredity – the transmission of characteristics from parents to offspring. Heredity BrainPop. Mendel’s Garden Peas. Mendel observed traits – characteristics coded from genes.

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Chapter 9 – Fundamentals of Genetics

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  1. Chapter 9 – Fundamentals of Genetics

  2. Gregor Mendel • Austrian monk • Experimented with pea plants. • Studied heredity – the transmission of characteristics from parents to offspring. Heredity BrainPop

  3. Mendel’s Garden Peas • Mendel observed traits – characteristics coded from genes. • He observed many traits of pea plants: height, flower position on stem, pod appearance, seed texture, seed color, and flower color.

  4. Mendel’s Methods • Mendel controlled how the pea plants pollinated so that he can track traits. • Pollination – pollen from male part of a flower, called the anthers are transferred to the female part of a flower, called the stigma. Gregor Mendel movie

  5. Pollination • Self-pollination – pollen is transferred to the stigma of the same flower. • Cross-pollination – pollen from one flower is transferred to the stigma of a different flower. • Which pollination will produce genetically diverse offspring?

  6. Mendel’s Experiments • He first grew plants that were pure for each trait. • Pure – plant that always produce offspring with that trait. • Ex. Tall plants self pollinate to produce tall plants.

  7. Terms to Know • P1 – first, parental generation • F1 – offspring of P1 generation • F2 – offspring of F1 generation Genetics 1 movie

  8. Mendel’s Results and Conclusions • Mendel crossed a pure tall plant with a pure short plant. • The result was all offspring was tall. • What happened to the short trait? • Traits are carried on alleles – form of a gene. Ex.) allele for Tall, allele for short (same trait but different variation). • Organisms have two alleles for one trait.

  9. Recessive and Dominant Traits • Dominant – an allele that masks another allele for that trait. Ex. Tall is dominant over short plants • Recessive – an allele that is masked by another allele for that trait. Ex. Short is dominant to tall plants. T = tall t = short Genetics 2 movie

  10. Law of Segregation • Alleles separate during the formation of gametes (Meiosis). • Only one allele of the parent is found in a gamete. • Ex. If a plant is has alleles Tt for height they will produce gametes with either T or t in them. Only one will be fertilized.

  11. The Law of Independent Assortment • Alleles for different traits are distributed to gametes independently. • Factors for different characteristics are not connected. • An offspring won’t have both alleles from its mother or father.

  12. Chromosomes and Genes • MolecularGenetics – study of structure and function of chromosomes and genes. Optional movie Heredity HOMEWORK Pg. 169 1-6

  13. 9-2 Genetic Crosses • The genetic makeup of an organism is its genotype. • The physical appearance of an organism is its phenotype. • Pea plant is tall = ________________ • Pea plant has Tt alleles = ______________ • Genetics 3 movie

  14. Genotypes • Homozygous – two alleles that are the same. Ex. TT, tt • Heterozygous – two alleles that are different. Ex. Tt

  15. Probability • Likelihood that an event will occur. Probability = number of times an event is expected to happen number of opportunities for an event to happen

  16. Probability • The recessive trait of yellow seed color appeared 6,022 times. • The recessive trait of green seed color appeared 2,001 times. • Total individuals is 8,023 What is the probability that the dominant trait will appear in a similar cross?

  17. 6,022/8,023 = 0.75 Expressed in percent ---- 75% dominant

  18. Predicting results of Monohybrid Crosses

  19. 11.3 Independent Assortment • DihybridCrosses – crossing two traits. Mendel crosses pea plants with two pairs of genes that were homozygous. 9:3:3:1 ratio

  20. Test Cross Problem - Peas RrYY x rrYy Round and yellow with wrinkled and yellow

  21. Probability Principle of Probability: each individual probability is independent and then multiplied together. (past outcomes do not effect future ones)

  22. Incomplete Dominance One allele is not completely dominant over another.

  23. Codominance • Both alleles contribute to the phenotype. • No blending, both alleles are expressed. Ex. Black horse x white horse black and white speckled horse

  24. Genetics 4 movie

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