Heredity Notebook Overview

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Overview of heredity

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Heredity Notebook Overview

  1. 1. HEREDITY “The Code of Life”
  2. 2. What is Genetics? (Chapter 1) <ul><li>Genetics is the study of heredity </li></ul><ul><li>Genetics is the study of how traits are passed from an organism to its offspring </li></ul>
  3. 3. Genetics <ul><li>Genetics helps to explain why living organisms: </li></ul><ul><li>Resemble their parents </li></ul><ul><li>Each have unique characteristics from any other living organism </li></ul>
  4. 4. History of Genetics <ul><li>Began with Gregor Mendel </li></ul><ul><li>in mid-1800’s </li></ul><ul><li>working with pea plants </li></ul><ul><ul><li>looking for a pattern in the way certain characteristics (or traits) are handed down from one generation to the next. </li></ul></ul>
  5. 5. Pea Plants <ul><li>Why were pea plants chosen? </li></ul><ul><li>Grow and reproduce quickly </li></ul><ul><li>Have a variety of characteristics (or traits) </li></ul><ul><li>Many traits ( list ) could be studied in one experiment </li></ul><ul><li>Can be crossed, or bred, easily </li></ul>
  6. 6. Reproductive Structures of Flowers <ul><li>Stamen = Male Sex Structure (pollen) </li></ul><ul><li>Pistil = Female Sex Structure (seeds) </li></ul>
  7. 7. Self-Pollination <ul><li>Pollen from the stamen (male) of one flower lands on the pistil (female) of the same flower , or a different flower on the same plant . </li></ul><ul><li>Since only one plant has been involved , it has pollinated it self . </li></ul>
  8. 8. Self-Pollination (Pure Tall x Pure Tall) X = Tall Tall Tall Tall Tall Tall Purebred Purebred Parents F 1 Generation (TT) (TT) (TT) (TT) (TT) (TT)
  9. 9. Self-Pollination (Pure Short x Pure Short) X = Short Short Short Short Short Short Purebred Purebred Parents F 1 Generation tt tt tt tt tt tt
  10. 10. Cross-Pollination <ul><li>Pollen from the stamen (male) of one flower lands on the pistil (female) of the flower of a different plant. </li></ul><ul><li>The pollen has crossed between two plants, hence cross-pollination. </li></ul>
  11. 11. Cross-Pollination (Pure Tall x Pure Short) X = Tall Short Tall Tall Tall Tall Hybrids Purebred Parents F 1 Generation TT tt Tt Tt Tt Tt
  12. 12. Cross-Pollination (Hybrid Tall x Hybrid Tall) X = Tall Tall Tall Tall Tall Short Hybrids Hybrids F 1 Generation F 2 Generation Purebred Purebred Tt Tt TT Tt Tt tt
  13. 13. “Father of Genetics” <ul><li>Gregor Mendel became known as the “Father of Genetics”. </li></ul><ul><li>He identified these traits as “characters” which we know call genes. </li></ul><ul><li>Genes are the units of heredity. </li></ul><ul><li>Genetics is the study of heredity, or the passing of traits from an organism to its offspring. </li></ul>
  14. 14. Dominant and Recessive <ul><li>Dominant means “ STRONG ” </li></ul><ul><li>Recessive means “ weak ” </li></ul><ul><li>Mendel found that some traits were stronger (dominant) while others were weaker (recessive). </li></ul><ul><li>Generally, letters are used to represent the gene </li></ul><ul><ul><li>Capital letter is used for the Dominant gene </li></ul></ul><ul><ul><li>Small letter is used for the Recessive gene </li></ul></ul>
  15. 15. Purebred vs. Hybrid <ul><li>Pure bred: If genes are alike for a particular trait </li></ul><ul><ul><li>Example: YY or yy </li></ul></ul><ul><li>Hybrid: If genes are different for a trait </li></ul><ul><ul><li>Example: Yy </li></ul></ul><ul><ul><li>NOTE: Hybrids are produced by crossing two purebred organisms with opposite traits </li></ul></ul>
  16. 16. Mendel’s Hypothesis <ul><li>Mendel made a hypothesis (suggested explanation) for the way traits were passed to the next generation </li></ul><ul><ul><li>Each trait must have a pair of factors, or genes, for each trait </li></ul></ul><ul><ul><li>Each plant in next generation also had a pair of genes for each trait, so must have received one from each parent. </li></ul></ul>
  17. 17. The Law of Segregation <ul><li>During the creation of the sex cells (sperm for the male, eggs for the female), the parent’s gene pairs must segregate (or separate). This is the Law of Segregation. </li></ul><ul><li>Sex cells carry half the gene pair for the new generation. So that after fertilization (union of sperm and egg), the new individual has the completed pair of genes. </li></ul>
  18. 18. Law of Segregation Yy Parent Y y Sex cell
  19. 19. Law of Independent Assortment <ul><li>This law states the each gene pair for a trait is inherited independently of the gene pairs for all other traits. </li></ul>Yy Tt Rr Ss Y y T t R r S s
  20. 20. Incomplete Dominance <ul><li>Sometimes, in the gene pairs, neither gene is dominant nor recessive. Neither gene has the ability to mask (hide) the other. As a result, the traits carried by the two genes appear to be blended. This is Incomplete Dominance. </li></ul>X = RR WW RW (red) (white) (pink)
  21. 21. Six Genetic Principles <ul><li>Traits, or characteristics, are passed on from one generation of organisms to the next generation. </li></ul><ul><li>The traits of an organism are controlled by genes. </li></ul><ul><li>Organisms inherit genes in pairs, one gene from each parent. </li></ul>
  22. 22. Six Genetic Principles (continued) <ul><li>Some genes are dominant, whereas other genes are recessive. </li></ul><ul><li>Dominant genes hide recessive genes when both are inherited by an organism. </li></ul><ul><li>Some genes are neither dominant nor recessive. These genes show incomplete dominance. </li></ul>
  23. 23. Genetics and Probability <ul><li>Probability is the possibility, or likelihood, that a particular event will occur. </li></ul><ul><li>Probability won’t tell us what WILL happen, BUT… </li></ul><ul><li>Probability can be used to predict the results of genetic crosses. </li></ul><ul><li>A probability is usually written as a fraction or a percentage. </li></ul>
  24. 24. Punnett Squares <ul><li>In addition to probability, a special chart called a Punnett square is used to show the possible gene combinations in a cross between two organisms. </li></ul><ul><li>The chart was developed by Reginald C. Punnett, an English geneticist. </li></ul>
  25. 25. Phenotype and Genotype <ul><li>The Phenotype refers to the physical appearance of an organism. </li></ul><ul><li>The Genotype is the actual gene makeup of the organism. </li></ul>
  26. 26. Phenotype and Genotypes BB bb Black White X Black Black Black Black Bb Bb Bb Bb Parents F 1 Generation (Purebred) (Purebred) Hybrid Hybrid Hybrid Hybrid
  27. 27. Phenotype and Genotypes (continued) Bb Bb Black Black X Black Black Black White BB Bb Bb bb F1 Generation F 2 Generation Purebred Purebred Hybrid Hybrid (Hybrid) (Hybrid)
  28. 28. Pea Plant Characteristics (or Traits) <ul><li>Tall vs. Short (T and t) </li></ul><ul><li>Round Seeds vs. Wrinkled Seeds (R and r) </li></ul><ul><li>Yellow Seeds vs. Green Seeds (Y and y) </li></ul><ul><li>Colored Seed Coat vs. White Seed Coat (C and c) </li></ul><ul><li>Full Pod vs. Pinched Pod (F and f) </li></ul><ul><li>Green Pod vs. Yellow Pod (G and g) </li></ul><ul><li>Side Flowers vs. End Flowers (S and s) </li></ul><ul><li>( return ) </li></ul>
  29. 29. Additional Links <ul><li>http://www.brooklyn.cuny.edu/bc/ahp/MGInv/MGI.Intro.html </li></ul><ul><li>http://anthro.palomar.edu/mendel/mendel_1.htm </li></ul><ul><li>http://www.brooklyn.cuny.edu/bc/ahp/BioInfo/GP/Definition.html </li></ul><ul><li>http://nces.ed.gov/nceskids/probability/ </li></ul><ul><li>http://nces.ed.gov/nceskids/Games.asp </li></ul>

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