Chapter 12 human genetics


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Chapter 12 human genetics

  1. 1. Chapter 12- Human Genetics
  2. 2. I. Human Heredity <ul><li>A. Human chromosomes </li></ul><ul><li>  </li></ul><ul><li>1. A picture of chromosomes arranged in a picture is called a karyotype. </li></ul>
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  4. 4. <ul><li>2. A normal human has 46 chromosomes, 23 pairs. </li></ul><ul><li>3. The number of chromosomes helps identify what the organism is. </li></ul><ul><li>  </li></ul><ul><li>4. Egg and sperm are haploid, containing half the amount of chromosomes-23. These cells are called sex cells. A female chromosomes is XX, a male is XY. </li></ul>
  5. 5. <ul><li>5. All other cells have 46 chromosomes in them, they are diploid. These cells are called autosomes. </li></ul><ul><li>  </li></ul><ul><li>6. All human egg cells carry a single X chromosome. </li></ul>
  6. 6. <ul><li>7. Half of all sperm cells carry an X and half carry a Y chromosome. </li></ul><ul><li>  </li></ul><ul><li>8. This ensures that just about half of the zygotes will be 46XX and the other half will be 46XY. </li></ul>
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  8. 8. B. Human Traits <ul><li>1. Human genes are inherited according to the same principals that Mendel discovered. </li></ul><ul><li>  </li></ul><ul><li>2. A pedigree chart shows relationships within a family. </li></ul>
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  10. 10. <ul><li>3. Genetic counselors analyze pedigree charts to infer the genotypes of family members. </li></ul><ul><li>  </li></ul><ul><li>4. Many traits are strongly influenced by environmental, or non-genetic factors, including nutrition and exercise. </li></ul>
  11. 11. C. Human Genes <ul><li>1. The human genome- our complete set of genetic information includes tens of thousands of genes. </li></ul><ul><li>  </li></ul><ul><li>2. Some of the very first genes to be identified were those that control blood type. </li></ul>
  12. 12. D. Blood Group Genes <ul><li>1. Human blood comes in a variety of genetically determined blood groups. </li></ul><ul><li>  </li></ul><ul><li>2. The different blood types are A, B, AB O plus there is a Rh+ or Rh- factor. </li></ul>
  13. 13. BLOOD GROUPS <ul><li>Phenotype Genotype Antigen Antibodies </li></ul><ul><li>A I A I A or I A I o A B </li></ul><ul><li>B I B I B or I B I o B A </li></ul><ul><li>AB I A I B A and B ------- </li></ul><ul><li>O I o I o -------- A and B </li></ul>
  14. 14. E. Recessive Alleles <ul><li>1. Many human genes have become known through the study of genetic disorders. </li></ul><ul><li>  </li></ul><ul><li>2. In most cases genetic disorders are USUALLY recessive. </li></ul><ul><li>  </li></ul><ul><li>3. See page 345 to see some disorders </li></ul>
  15. 15. Albinism
  16. 16. Cystic Fibrosis
  17. 17. Dwarfism
  18. 18. Sickle Cell Disease
  19. 19. F. Dominant Alleles <ul><li>1. Not all genetic disorders are caused by a recessive allele. </li></ul><ul><li>  </li></ul><ul><li>2. Two examples of a genetic disorder caused by autosomal dominant alleles are dwarfism and Huntington ’ s disease. </li></ul>
  20. 20. Huntington’s disease
  21. 21. G. Codominant alleles <ul><li>1. Sickle cell disease is caused by a codominant allele. </li></ul>
  22. 22. H. From Gene to molecule <ul><li>1. In both cystic fibrosis and sickle cell disease, a small change in the DNA of a single gene affects the structure of a protein, causing a series genetic disorder. </li></ul><ul><li>  </li></ul><ul><li>2. CF is most common among people with Northern Europe ancestors. </li></ul>
  23. 23. <ul><li>3. People with CF have serious digestive problems in addition they produce thick, heavy mucus that clogs their lungs and breathing passageways. </li></ul><ul><li>  </li></ul><ul><li>4. Sickle cell is a disease found in African American ’ s. </li></ul>
  24. 24. <ul><li>3. It is a bent and twisted shape of the RBC ’ s. </li></ul><ul><li>  </li></ul><ul><li>4.   As a result, blood stops moving through these vessels, damaging cells, tissues and organs. </li></ul><ul><li>  </li></ul><ul><li>5. Sickle cell disease produces physical weakness, and damage to the brain, heart, and spleen. </li></ul>
  25. 25. II. Human Chromosomes <ul><li>A. Human Genes and Chromosomes </li></ul><ul><li>1. Chromosomes 21 and 22 are the smallest human autosomes. Chromosome 22 contains 43 million DNA base pairs! Chromsomes 21 contains about 32 million! </li></ul><ul><li>  </li></ul><ul><li>2. MILLIONS of base pairs! </li></ul>
  26. 26. B. Sex Linked Genes <ul><li>1. Many sex-linked genes are found on the X chromosomes. More than 100 sex-linked genetic disorders are found on the X. </li></ul><ul><li>  </li></ul><ul><li>2. Males have just one X chromosome, thus all X-linked alleles are expressed in males even if they are recessive. </li></ul>
  27. 27. <ul><li>3. Some sex-linked disorders are colorblindness, hemophilia, and Duchenne muscular dystrophy. </li></ul>
  28. 28. C. Color Blindness <ul><li>1. The most common disorder is red-green colorblindness affecting 1 in 10 males in the US. </li></ul><ul><li>  </li></ul><ul><li>2. Among females colorblindness is only 1-100. </li></ul>
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  33. 33. D. Hemophilia <ul><li>1. Two important genes carried on the X chromosome help blood to clot. </li></ul><ul><li>  </li></ul><ul><li>2. In hemophilia, a protein necessary for normal blood clotting is missing. </li></ul><ul><li>  </li></ul><ul><li>3. About 1 in 10,000 males is born with hemophilia. </li></ul>
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  35. 35. E. Duschenne Muscular dystrophy <ul><li>1. This is a disorder that results in the progressive weakening and loss of skeletal muscles. </li></ul><ul><li>  </li></ul><ul><li>2. In the US 1 out of 3000 males are born with this. </li></ul>
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  37. 37. F. X-Chromosome Inactivation <ul><li>1. Females have 2 X chromosomes, but males have only 1. </li></ul><ul><li>  </li></ul><ul><li>2. In female cells, one X chromosome is randomly switched off. </li></ul>
  38. 38. G. Chromosomal disorders <ul><li>1. The most common error in meiosis occurs when homologous chromosomes fail to separate. This is known as nondisjunction. </li></ul><ul><li>  </li></ul><ul><li>2. If nondisjunction occurs, abnormal numbers of chromosomes may find their way into gametes, and a disorder of chromosome numbers may result. </li></ul>
  39. 39. <ul><li>3. IF two copies of an autosomal chromosome fail to separate during meiosis, an individual may be born with three copies of a chromosome. </li></ul><ul><li>  </li></ul><ul><li>4. This is known as trisomy </li></ul>
  40. 40. <ul><li>5. The most common trisomy is down syndrome- having an extra chromosome on pair number 21. </li></ul><ul><li>  </li></ul><ul><li>6. 1-800 babies are born with Down syndrome. </li></ul>
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  42. 42. <ul><li>7. Disorders also occur among the sex chromosomes. Two of these are Turner syndrome and Klienefelter ’ s. </li></ul><ul><li>  </li></ul><ul><li>8. In Turner syndrome there is only 1 X. The female is sterile and their sex organs do not develop at puberty. </li></ul>
  43. 43. <ul><li>9. In males, Klinefelter ’ s has an extra X, XXY, XXXY or even XXXXY. </li></ul>
  44. 44. <ul><li>10. There have been no reported cases of babies being born without the X chromosome, indicating that the X chromosome contains genets that are vital for the survival and development. </li></ul>
  45. 45. III. Human Molecular Genetics <ul><li>A. Human DNA analysis </li></ul><ul><li>  </li></ul><ul><li>1. DNA fingerprinting is used by molecular biology to identify individuals. </li></ul>
  46. 46. <ul><li>2. The human genome project is an ongoing effort to analyze the human DNA sequence. </li></ul><ul><li>  </li></ul><ul><li>3. In gene therapy, an absent or faulty gene is replaced by a normal, working gene. </li></ul>
  47. 47. <ul><li>4. It would be great to cure genetic disorders= BUT, if human cells can be manipulated to cure disease, should biologists try to engineer taller people or change their eye color, ect? </li></ul>
  48. 48. The END