Chapter 9+12 Notes


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Chapter 9+12 Notes

  1. 1. Chapter 9+12 Fundamentals of Genetics And Human Genetics
  2. 2. Gregor Mendel <ul><li>Austrian monk that studied heredity. </li></ul><ul><li>Heredity is the transmission of characteristics from parents to offspring </li></ul><ul><li>Experimented with pea plants in the garden to determine what traits were passed along. </li></ul><ul><li>He discovered the basic rules of genetics. </li></ul>
  3. 3. Pea Plants <ul><li>Mendel studied 7 traits. </li></ul><ul><li>They were easily observable: plant height, flower position, pod color, pod appearance, seed texture, seed color and flower color. </li></ul><ul><li>Mendel used cross pollination in his studies to make sure each parent was the correct one he wanted. </li></ul>
  4. 5. Important Vocabulary <ul><li>Pure- being a purebreed, parent always passes on one trait to the offspring </li></ul><ul><li>P 1 generation-parent or first generation </li></ul><ul><li>F 1 -filial generation or kids of the parent generation </li></ul><ul><li>F 2 - grandkids of the parent generation </li></ul>
  5. 6. Important Vocabulary <ul><li>Dominant- a trait that always shows up in the F 1 generation, it is the strongest trait and will mask other traits </li></ul><ul><li>Recessive- a trait that is weaker, usually doesn’t appear in F 1 generation but appears in F 2 generation </li></ul><ul><li>Mendel discovered that certain traits were dominant and certain ones were recessive. </li></ul><ul><li>Look in your book for the list of traits. </li></ul>
  6. 9. Mendel’s Laws <ul><li>The Law of Segregation states that paired factors separate during the formation of gametes (meiosis) </li></ul><ul><li>Each gamete only receives one factor or trait from each parent. </li></ul><ul><li>The Law of Independent Assortment sates that factors for different traits distribute to gametes independently regardless of the other trait. </li></ul>
  7. 10. Important Vocabulary <ul><li>An allele is the factor or gene that is passed only; it is a type of gene. </li></ul><ul><li>There may be several alleles for one gene. </li></ul><ul><li>Dominant alleles have capital letters and recessive alleles have lowercase letters. </li></ul><ul><li>Genotype is the actual genetic makeup of the organism or what the genes say. </li></ul><ul><li>Phenotype is the physical look of the organism like color or texture. </li></ul><ul><li>You can see the phenotype but not the genotype. </li></ul>
  8. 11. YY yy fertilization ? Y Y y y Yy Yy Yy Yy What is the phenotype of the offspring? The phenotype is yellow seed color.
  9. 12. Important Vocabulary <ul><li>Homozygous means the organism has two of same alleles for a trait. </li></ul><ul><li>Heterozygous means the organism has two different alleles for a trait. </li></ul><ul><li>Heterozygous would automatically have one dominant allele and one recessive allele. </li></ul><ul><li>Homozygous could have two dominant alleles or two recessive alleles. </li></ul>
  10. 13. AA aa Aa homozygous heterozygous
  11. 15. Incomplete Dominance (intermediate) <ul><li>When two or more alleles influence the phenotype, both are expressed so neither is completely dominant or recessive. </li></ul><ul><li>This results in a third phenotype in addition to the originals. </li></ul><ul><li>The heterozygous genotype is always the new phenotype. </li></ul>
  12. 18. Codominance <ul><li>This results when two or more alleles are equally dominant and both alleles are expressed in heterozygous organisms </li></ul><ul><li>Both alleles are expressed equally. </li></ul><ul><li>This is different than incomplete dominance because it isn’t a blended phenotype, is both expressed. </li></ul><ul><li>Human blood type is an example. </li></ul>
  13. 20. Sex Linked Inheritance <ul><li>Some genes are found only on the X-chromosome. </li></ul><ul><li>Many disease are X-linked diseases and are more common in males than in females. </li></ul><ul><li>Males need only one copy of the bad gene while females need two copies of the bad gene. </li></ul><ul><li>Hemophilia, colorblindness and Duchenne muscular dystrophy are human diseases associated with this inheritance. </li></ul><ul><li>A carrier is heterozygous for a disease but does not have the disease. It can be passed on to their children though. </li></ul><ul><li>Sex-influences traits like baldness are influenced by the sex of the person and are expressed differently even if the gene is the same. </li></ul>
  14. 21. Important Vocabulary <ul><li>Polygenic traits are controlled by more than one gene. </li></ul><ul><li>Skin color is controlled by at lease six genes which result is a different amount of pigment produced. </li></ul><ul><li>Eye color is also polygenic as well as height although environment plays a part in that as well. </li></ul>
  15. 23. Mutations <ul><li>Down syndrome results when the chromosomes don’t split evenly during meiosis resulting in three chromosomes under number 21. </li></ul><ul><li>Turner’s syndrome also occurs this way and results in one less sex chromosome. </li></ul><ul><li>Disorders can also be inherited recessively or dominantly or even as a result of chromosome pieces breaking off or “jumping” around. </li></ul>
  16. 25. A carrier is heterozygous for a disease but does not have the disease.
  17. 28. Why would it be advantageous to be heterozygous for sickle cell trait when sickle cell is so dangerous? 1 in 500 African Americans have sickle cell anemia. 1 in 12 carry the sickle cell gene.