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Classical Genetics


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Basic Mendelian Genetics based on BSCS Blue and Campbell Biology

Published in: Lifestyle, Business

Classical Genetics

  1. 1. Classical Genetics
  2. 2. The Work and Conclusions of Gregor Mendel Father of genetics Monk in Austria 1865 Studied patterns of inheritance in peas
  3. 3. Why Peas?
  4. 4. Why Peas? Self-fertilization produces true breeding generations
  5. 5. <ul><li>Prevented self-fertilization </li></ul><ul><li>Manipulated reproduction </li></ul><ul><li>Began monohybrid crosses </li></ul><ul><li>Carefully examined results </li></ul>Why Peas? Read Concept 1 Click Animation and View
  6. 6. Why Peas? Read Concept 2 Click Animation and View
  7. 7. Mendel’s Work Some traits are dominant and some are recessive Read concept 3 Click animation and view Read concept 4 Click animation and view
  8. 8. Mendel’s Work <ul><li>Traits are passed on by factors (genes) </li></ul><ul><li>Factors (genes) have more than 1 form called alleles </li></ul><ul><li>There are at least 2 alleles for each trait </li></ul>
  9. 9. Mendel’s Work Alleles are represented by the first letter of the dominant trait Pea plant flower color (trait) Purple or white Purple is dominant over white Alleles are represented as P=purple p=white
  10. 10. <ul><li>You try a few… </li></ul><ul><li>Round seeds are dominant over wrinkled seeds </li></ul><ul><li>Yellow seeds are dominant over green seeds </li></ul><ul><li>Tall plants are dominant over short plants </li></ul><ul><li>1. R=round r=wrinkled </li></ul><ul><li>Y=yellow y=green </li></ul><ul><li>T=tall t= short </li></ul>Mendel’s Work
  11. 11. Mendel’s Work Describing Traits (Tall or short plants) Genotype The actual genetic make-up of an organism the “genes” Phenotype The physical appearance or form observed the “physical”
  12. 12. Mendel’s Work Possible Genotypes (TT Tt tt) Homozygous The two alleles for the trait are identical TT homozygous dominant (purebred dominant) tt homozygous recessive (purebred recessive) Heterozygous The two alleles for the trait are different Tt heterozygote (hybrid)
  13. 13. Mendel’s Work
  14. 14. Mendel’s Work Read Concept 5 Click animation and view Complete visual organizer of Mendel’s pea plant experiment
  15. 15. 1. Law of Dominance Alleles for a trait are either dominant or recessive The dominant form is expressed and the recessive form is hidden The only way to express a recessive trait is if there are two copies of the recessive allele Mendel’s Conclusions
  16. 17. Mendel’s Conclusions <ul><li>Law of Segregation </li></ul><ul><li>The two alleles for a trait separate during gametogenesis </li></ul>
  17. 18. Test Cross
  18. 19. Dihybrid Cross
  19. 20. Mendel’s 3 rd Law of Independent Assortment <ul><li>Alleles of different genes are assorted independently of one another during the formation of gametes </li></ul><ul><li>This means that calculating the probability of several traits appearing together is the product of the probability of each trait taken separately </li></ul><ul><li>The Rule of Multiplication </li></ul>
  20. 21. Incomplete Dominance
  21. 22. “ Dominant” gene does not fully express itself to mask the effect of the recessive gene A pattern of inheritance in which the phenotype of a heterozygous individual is intermediate between those of the parents Genotypic ratio is equal to phenotypic ratio
  22. 23. Co-Dominance Two or more alleles are fully dominant When present together they are both expressed ABO Blood Groups exhibit co-dominace
  23. 24. Type A Blood <ul><li>• Individuals with group A blood have red blood </li></ul><ul><li>cells with antigen A on their surface. </li></ul><ul><li>Produce antibodies against antigen B, </li></ul><ul><li>antibody B. </li></ul><ul><li>• Therefore, a group A person can only receive </li></ul><ul><li>blood from people in groups A or O </li></ul>
  24. 25. Type B Blood <ul><li>Antigen B is on their cells, and antibodies A are produced in their serum. </li></ul><ul><li>A group B person can only receive blood from people in groups B or O, preferably B. </li></ul>
  25. 26. Type AB <ul><li>Individuals with group AB blood have red blood cells with both antigens A and B. </li></ul><ul><li>Do not produce antibodies A or B against either antigen in their serum. </li></ul><ul><li>A person with type AB blood can receive blood from any group (preferably AB) but cannot donate blood except to another AB. </li></ul>
  26. 27. Type O <ul><li>Individuals with group O blood have red blood cells with neither antigen A or B. </li></ul><ul><li>Produce antibodies A and B against both types of antigens. </li></ul><ul><li>A group O person can only receive blood from group O. </li></ul>
  27. 32. Sex Inheritance Sex Chromosomes X or Y XX is female XY is male Read concept 9 Click animation and view
  28. 33. Sex-Linked Inheritance Genes linked to sex chromosomes