Mendel

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Mendel

  1. 1. Mendel’s Laws of Heredity Why we look the way we look...
  2. 2. What is heredity ? <ul><li>The passing on of characteristics (traits) from parents to offspring </li></ul><ul><li>Genetics is the study of heredity </li></ul>
  3. 3. Mendel used peas... <ul><li>They reproduce sexually </li></ul><ul><li>They have two distinct, male and female , sex cells called gametes </li></ul><ul><li>Their traits are easy to isolate </li></ul>
  4. 4. Mendel crossed them <ul><li>Fertilization - the uniting of male and female gametes </li></ul><ul><li>Cross - combining gametes from parents with different traits </li></ul>
  5. 5. Questions <ul><li>What did Mendel cross? </li></ul><ul><li>What are traits ? </li></ul><ul><li>What are gametes ? </li></ul><ul><li>What is fertilization ? </li></ul><ul><li>What is heredity ? </li></ul><ul><li>What is genetics ? </li></ul>
  6. 6. What Did Mendel Find? <ul><li>He discovered different laws and rules that explain factors affecting heredity . </li></ul>
  7. 7. Rule of Unit Factors <ul><li>Each organism has two alleles for each trait </li></ul><ul><ul><ul><li>Alleles - different forms of the same gene </li></ul></ul></ul><ul><ul><ul><li>Genes - located on chromosomes, they control how an organism develops </li></ul></ul></ul>
  8. 8. Rule of Dominance <ul><li>The trait that is observed in the offspring is the dominant trait (uppercase) </li></ul><ul><li>The trait that disappears in the offspring is the recessive trait (lowercase) </li></ul>
  9. 9. Law of Segregation <ul><li>The two alleles for a trait must separate when gametes are formed </li></ul><ul><li>A parent randomly passes only one allele for each trait to each offspring </li></ul>
  10. 10. Law of Independent Assortment <ul><li>The genes for different traits are inherited independently of each other. </li></ul>
  11. 11. Questions... <ul><li>How many alleles are there for each trait? </li></ul><ul><li>What is an allele ? </li></ul><ul><li>How many alleles does a parent pass on to each offspring for each trait </li></ul>
  12. 12. Questions... <ul><li>What do we call the trait that is observed ? </li></ul><ul><li>What case (upper or lower) is it written in? </li></ul><ul><li>What about the one that disappears ? </li></ul><ul><li>What case is it written in? </li></ul>
  13. 13. Phenotype & Genotype <ul><li>Phenotype - the way an organism looks </li></ul><ul><ul><ul><li>red hair or brown hair </li></ul></ul></ul><ul><li>genotype - the gene combination of an organism </li></ul><ul><ul><ul><li>AA or Aa or aa </li></ul></ul></ul>
  14. 14. Heterozygous & Homozygous <ul><li>Heterozygous - if the two alleles for a trait are different ( Aa ) </li></ul><ul><li>Homozygous - if the two alleles for a trait are the same ( AA or aa ) </li></ul>
  15. 15. Dihybrid vs Monohybrid <ul><li>Dihybrid Cross - crossing parents who differ in two traits ( AAEE with aaee ) </li></ul><ul><li>Monohybrid Cross - crossing parents who differ in only one trait ( AA with aa ) </li></ul>
  16. 16. Questions... <ul><li>What is the phenotype ? </li></ul><ul><li>What is the genotype ? </li></ul><ul><li>What is homozygous ? </li></ul><ul><li>What is heterozygous ? </li></ul><ul><li>What is monohybrid crossing ? </li></ul>

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