Genetics

4,368 views

Published on

Published in: Education, Lifestyle, Technology

Genetics

  1. 1. Genetics Chapter 11
  2. 2. Gregor Mendel <ul><li>“ Father” of genetics </li></ul><ul><li>Austrian monk, mid-1800s </li></ul><ul><li>Researched pea plant inheritance </li></ul><ul><ul><li>Easy to grow, fast reproduction </li></ul></ul><ul><ul><li>Studied plant height, pea shape/color, pod color, etc. </li></ul></ul>
  3. 4. Pea Plant Reproduction <ul><li>Self-pollination </li></ul><ul><ul><li>Male gametes (pollen) fertilize egg of same flower </li></ul></ul><ul><ul><li>Produces pure-bred offspring </li></ul></ul><ul><ul><li>True-breeding: produce offspring identical to parent when self-pollinated </li></ul></ul>
  4. 5. Pea Plant Reproduction <ul><li>Cross-pollination </li></ul><ul><ul><li>Pollen from one plant fertilizes egg of another plant </li></ul></ul><ul><ul><li>Offspring have two parents </li></ul></ul>
  5. 6. Mendel’s Experiments <ul><li>P = Parent generation </li></ul><ul><li>F 1 = First filial generation </li></ul><ul><li>F 2 = Second filial generation (F 1 X F 1 ) </li></ul><ul><ul><ul><ul><li>Outcome </li></ul></ul></ul></ul><ul><li>P Pure Green X Pure Yellow </li></ul><ul><li>F 1 All Green </li></ul><ul><li>F 2 3 Green:1 Yellow </li></ul>
  6. 8. Mendel’s Conclusions <ul><li>Law of Dominance – one allele (form of a gene) is dominant, one is recessive </li></ul><ul><ul><li>Recessive trait was hidden in F 1 generation </li></ul></ul><ul><ul><li>Green = dominant </li></ul></ul><ul><ul><li>Yellow = recessive </li></ul></ul>
  7. 9. Mendel’s Conclusions <ul><li>Law of Segregation: alleles for a gene separate when gametes form (meiosis I) </li></ul><ul><ul><li>Each gamete gets one copy of each gene </li></ul></ul>
  8. 10. Some Vocab. <ul><li>Genotype – allele combination </li></ul><ul><ul><li>Capital letter = dominant allele </li></ul></ul><ul><ul><li>Lowercase letter = recessive allele </li></ul></ul><ul><ul><li>Ex – AA, Aa, aa </li></ul></ul><ul><li>Phenotype – physical appearance </li></ul><ul><ul><li>Ex – green, yellow </li></ul></ul>
  9. 11. Some Vocab. <ul><li>Homozygous – two alleles same </li></ul><ul><ul><li>Homozygous dominant: AA </li></ul></ul><ul><ul><li>Homozygous recessive: aa </li></ul></ul><ul><li>Heterozygous – two alleles different </li></ul><ul><ul><li>Aa </li></ul></ul>
  10. 12. Punnett Squares <ul><li>First must determine possible gametes </li></ul><ul><li>Heterozygous tall plant = Tt </li></ul><ul><ul><li>Half of gametes will get ‘T’, other half will get ‘t’ </li></ul></ul><ul><li>Homozygous tall plant = TT </li></ul><ul><ul><li>All gametes will get ‘T’ </li></ul></ul>
  11. 13. Punnett Squares <ul><li>Monohybrid cross </li></ul><ul><ul><li>Cross involving one trait </li></ul></ul><ul><li>Gametes go on the top and side </li></ul><ul><li>Combine gametes to find possible offspring </li></ul>Tt X Tt
  12. 14. Punnett Squares <ul><li>Genotype ratio </li></ul><ul><li>1TT: 2Tt: 1tt </li></ul><ul><li>Phenotype ratio </li></ul><ul><li>3 tall: 1 short </li></ul>Tt X Tt
  13. 15. Probability <ul><li>Punnett squares are used to predict the probability of certain traits in offspring of genetic crosses </li></ul><ul><li>Tt X Tt </li></ul><ul><ul><li>½ chance of getting ‘t’ from mom, ½ chance of getting ‘t’ from dad </li></ul></ul><ul><ul><li>½ X ½ = ¼ tt in offspring </li></ul></ul>
  14. 16. Dihybrid Cross <ul><li>Mendel looked at the inheritance patterns of two traits </li></ul><ul><ul><li>Seed shape and seed color </li></ul></ul><ul><li>Found that the traits were inherited independently of each other </li></ul><ul><li>Law of Independent Assortment </li></ul><ul><ul><li>Genes on separate chromosomes are inherited at random </li></ul></ul><ul><ul><li>Due to random chromosome shuffling in Metaphase I </li></ul></ul>
  15. 17. Independent Assortment Metaphase I
  16. 19. Non-Mendelian Genetics <ul><li>Not all traits follow Mendel’s Law of Dominance </li></ul><ul><li>Four Variations </li></ul><ul><ul><li>Incomplete Dominance (blending) </li></ul></ul><ul><ul><li>Codominance (two phenotypes) </li></ul></ul><ul><ul><li>Multiple Alleles </li></ul></ul><ul><ul><li>Polygenic Traits </li></ul></ul>
  17. 20. Incomplete Dominance <ul><li>Neither allele is dominant, both produce a protein </li></ul><ul><li>Heterozygous phenotype is a blend of both homozygous phenotypes </li></ul><ul><li>Ex – wavy hair, pink flowers </li></ul>
  18. 21. Incomplete Dominance
  19. 22. Codominance <ul><li>Neither allele dominates the other, both produce a protein </li></ul><ul><li>Heterozygous phenotype is a combination of both homozygous phenotypes </li></ul><ul><li>Ex – checkered chicken, human blood types, </li></ul>
  20. 24. Multiple Alleles <ul><li>Some genes have more than two alleles </li></ul><ul><li>Each individual only gets two, but there are more than two in the population </li></ul><ul><li>Ex – Rabbit fur color </li></ul>
  21. 25. Multiple Alleles <ul><li>Rabbit fur alleles (in order of dominance) </li></ul><ul><ul><li>C: dark gray </li></ul></ul><ul><ul><li>c ch : chinchilla </li></ul></ul><ul><ul><li>c h : himalayan </li></ul></ul><ul><ul><li>c: albino </li></ul></ul>
  22. 26. Multiple Alleles
  23. 27. Polygenic Traits <ul><li>Many traits are controlled by more than one gene </li></ul><ul><li>Traits show wide variation </li></ul><ul><li>Ex – human height, IQ, bell pepper colors </li></ul>

×