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Chapter 5 Genetics

Chapter 5 Genetics. Mendel and His Peas. Early Ideas About Heredity. Blending Inheritance – early ideas of mixing of traits like mixing of paint. Gregor Mendel disproved this idea. Father of genetics Genetics - study of heredity

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Chapter 5 Genetics

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  1. Chapter 5Genetics

  2. Mendel and His Peas

  3. Early Ideas About Heredity • Blending Inheritance – early ideas of mixing of traits like mixing of paint. • Gregor Mendel disproved this idea. • Father of genetics • Genetics - study of heredity • Heredity – the passing of traits from parents to offspring

  4. Mendel’s Experimental Methods • Controlled Pea Plant Experiments • Why the Pea Plant? • Reproduce quickly • Easily observed traits • Controlled which plants reproduced

  5. Pollination in Pea Plants • Pollination – pollen (sperm) lands on a pistil (egg) of a flower. • Self-pollination – pollen to pistil; same plant • Cross-pollination – pollen to pistil; different plants - wind, water, or animals

  6. Mendel’s Experiment • First Step – Allow plants to true-breed (self-pollinate) which provided offspring with traits that matched the parents. (First-Generation) • Second Step – Controlled cross-pollination of the First-Generation by removing the stamens of one flower and pollinating that flower with pollen from a flower of a different plant. (Second-Generation/Hybrid) • Third Step – Allow Second Generation/Hybrid plants to self-pollinate.

  7. Mendel’s Results • Self-Pollination/True Breeding • Same traits as parent • Purple produced Purple • White produced White • Controlled Cross-Pollination of First-Generations • Only Purple offspring are produced • Purple First Generation crossed with White First Generation • Hybrids • Self-Pollination of Hybrids • Reappearance of traits First-Generation

  8. Mendel’s Conclusion • Two genetic factors control each inherited trait. • When organisms reproduce, each reproductive cell, sperm or egg, contributed one factor for each trait. • Dominant trait – a genetic factor that blocks another genetic factor. (one or two dominant factors can be present for expression) • Recessive trait – a genetic factor that is blocked by the presence of a dominant factor. (both recessive factors must be present for expression)

  9. Lesson 1 Review pg. 156 #’s 1 - 10

  10. Understanding Inheritance

  11. What Controls Traits? • Chromosomes – found in the nucleus - carry traits from mom and dad • Gene – a section on a chromosome that has genetic information for one trait. - ex. Flower color Height • Allele – different forms of a gene - represented by letters of upper or lower case. - ex. P = Purple p = white

  12. Genotype & Phenotype • Phenotype – how a trait appears or is expressed ex. Eye Color (Blue) (Brown) • Genotype – the two alleles that control the phenotype of a trait. SYMBOLS ex. Eye Color (bb)= Blue (BB or Bb) = Brown TABLE 2 pg. 161 Homozygous Dominant Heterozygous – when two alleles are different for a trait. This would be called Heterozygous Homozygous – when the two alleles for a gene are the same. This would be called Homozygous Recessive

  13. Punnett Squares • Probability – chance of getting an outcome. ex. Flipping a coin 2 total possibilities Heads = 1 of 2 (50%) Tails = 1 of 2 (50%) • Punnett Square – model used to predict possible genotypes and phenotypes of offspring. Ratio Probability

  14. Pedigrees • Pedigree – shows phenotypes of genetically related family members. • helps determine genotypes

  15. Complex Patterns of Inheritance • Incomplete Dominance – offspring’s phenotype is a combination of the parents phenotype. ex. Red Camellia White Camellia Pink Camellia • Codominance – two alleles can be observed in a phenotype. ex. White Coat Cow Red Coat Cow Roan Coat Cow

  16. Complex Patterns of Inheritance • Multiple Alleles – more than two alleles for a trait. ex. Blood Type - 3 different alleles for apossible 4 different blood types. - can only inherit one from each parent IA IBi Codominant to each other recessive Type A Blood = IA IAorIaI Type B Blood = IB IBorIB i Type OBlood = ii Type AB Blood = IA IB

  17. Polygenic Inheritance • Polygenic Inheritance – multiple genes determine the phenotype of a trait giving many possible phenotypes. ex. Skin color

  18. Genes and the Environment • Environment • Soil acidity in flowers (hydrangea) • Healthy choices (heart disease) • Body temperature (siamese cat) • Seasonal development (arashnialevana butterfly)

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