Human Genetics I

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Human Genetics I

  1. 2. HUMAN GENETICS
  2. 3. HUMAN GENETICS <ul><li>1. WHAT ARE SOME EXAMPLES IN HUMANS OF CHROMOSOMAL EFFECTS? </li></ul><ul><li>2. WHAT ARE SOME EXAMPLES IN HUMANS OF AUTOSOMAL DOMINANT AND RECESSIVE TRAITS? </li></ul>
  3. 4. HUMAN GENETICS <ul><li>3. WHAT ARE SOME OTHER FORMS OF INHERITANCE IN HUMANS? </li></ul><ul><li>4. WHAT IS A PEDIGREE? </li></ul><ul><li>5. HOW CAN GENETIC DISORDERS BE DETECTED? </li></ul>
  4. 5. 1. WHAT ARE SOME EXAMPLES IN HUMANS OF CHROMOSOMAL EFFECTS?
  5. 6. Chromosomal Inheritance <ul><li>All but one pair of chromosomes in males and females are the same. </li></ul><ul><ul><li>Autosomes - Nonsex chromosomes </li></ul></ul><ul><li>The different pair, sex chromosomes, determines the sex of an individual. </li></ul><ul><ul><li>X-linked (sex-linked) is the term used for genes carried on the X chromosome. </li></ul></ul>
  6. 7. X-Linked Alleles <ul><li>X-linked alleles have a different pattern of inheritance than alleles on autosomes because the Y chromosome is blank for these alleles. </li></ul><ul><ul><li>Inheritance of a Y chromosome cannot offset the inheritance of an X-linked recessive allele. </li></ul></ul>
  7. 8. Human X-Linked Disorders <ul><li>Color Blindness </li></ul><ul><ul><li>In humans, color vision receptors in the retina are three different classes of cone cells. </li></ul></ul><ul><ul><ul><li>Only one type of pigment is present in each class of cone cell. </li></ul></ul></ul><ul><ul><ul><ul><li>The allele for blue-sensitive is autosomal, but the red- and green-sensitive proteins are on the X chromosome. </li></ul></ul></ul></ul>
  8. 9. Human X-Linked Disorders <ul><li>Muscular Dystrophy </li></ul><ul><ul><li>Absence of protein dystrophin allows calcium to leak into muscle cells. </li></ul></ul><ul><li>Hemophilia </li></ul><ul><ul><li>Hemophilia A due to lack of clotting factor IX and hemophilia B due to lack of clotting factor VIII. </li></ul></ul>
  9. 10. Changes in Chromosome Number <ul><li>Monosomy and Trisomy </li></ul><ul><ul><li>Monosomy (2n - 1) occurs when an individual has only one of a particular type of chromosome. </li></ul></ul><ul><ul><li>Trisomy (2n + 1) occurs when an individual has three of a particular type of chromosome. </li></ul></ul>
  10. 13. Changes in Sex Chromosome Number <ul><li>An abnormal sex chromosome number is the result of inheriting too many or too few X or Y chromosomes. </li></ul><ul><ul><li>Nondisjunction during oogenesis or spermatogenesis. </li></ul></ul>
  11. 15. TURNER SYNDROME X0 TURNER SYNDROME XO KLINEFELTER XXY
  12. 16. Sex Chromosome Syndromes <ul><li>Poly-X Females </li></ul><ul><ul><li>More than two X chromosomes and extra Barr bodies in the nucleus. </li></ul></ul><ul><ul><ul><li>Range from tall and thin to tall and severely retarded depending on number of X chromosomes. </li></ul></ul></ul><ul><li>Jacobs Syndrome </li></ul><ul><ul><li>XXY due to nondisjunction during spermatogenesis. </li></ul></ul><ul><ul><ul><li>Taller than average </li></ul></ul></ul>
  13. 18. Changes in Chromosome Structure <ul><li>Deletion </li></ul><ul><ul><li>End of a chromosome breaks off, or two simultaneous breaks lead to loss of an internal segment. </li></ul></ul><ul><li>Translocation </li></ul><ul><ul><li>Movement of a chromosome segment from one chromosome to another, non-homologous chromosome. </li></ul></ul>
  14. 20. WILLIAMS SYNDROME
  15. 22. ALAGILLE SYNDROME
  16. 23. Changes in Chromosome Structure <ul><li>Duplication </li></ul><ul><ul><li>Presence of chromosomal segment more than once in the same chromosome. </li></ul></ul><ul><ul><ul><li>Known to occur as a result of an inversion in which segment is turned 180 o . </li></ul></ul></ul>
  17. 26. 2. WHAT ARE SOME EXAMPLES IN HUMANS OF AUTOSOMAL DOMINANT AND RECESSIVE TRAITS?
  18. 27. Human Genetic Disorders <ul><li>Autosome - Any chromosome other than a sex chromosome. </li></ul><ul><ul><li>When a genetic disorder is autosomal dominant, an individual with AA or Aa has the disorder. </li></ul></ul><ul><ul><li>When a genetic disorder is autosomal recessive, only aa individuals have the disorder. </li></ul></ul><ul><ul><ul><li>Carriers - Individuals unaffected by a disorder but can have an affected child. </li></ul></ul></ul>
  19. 28. Human Genetic Disorders <ul><li>Autosome - Any chromosome other than a sex chromosome. </li></ul><ul><ul><li>When a genetic disorder is autosomal dominant, an individual with AA or Aa has the disorder. </li></ul></ul><ul><ul><li>When a genetic disorder is autosomal recessive, only aa individuals have the disorder. </li></ul></ul><ul><ul><ul><li>Carriers - Individuals unaffected by a disorder but can have an affected child. </li></ul></ul></ul>
  20. 29. Autosomal Recessive Disorders <ul><li>Tay-Sachs Disease </li></ul><ul><ul><li>Progressive deterioration of psychomotor functions. </li></ul></ul><ul><li>Cystic Fibrosis </li></ul><ul><ul><li>Mucus in bronchial tubes and pancreatic ducts is particularly thick and viscous. </li></ul></ul><ul><li>Phenylketonuria </li></ul><ul><ul><li>Lack enzyme for normal metabolism of phenylalanine. </li></ul></ul>
  21. 30. Autosomal Dominant Disorders <ul><li>Neurofibromatosis </li></ul><ul><ul><li>Tan or dark spots develop on skin and darken. Small, benign tumors may arise from fibrous nerve coverings. </li></ul></ul><ul><li>Huntington Disease </li></ul><ul><ul><li>Neurological disorder leading to progressive degeneration of brain cells, in turn causing severe muscle spasms and personality disorders. </li></ul></ul>
  22. 31. 3. WHAT ARE SOME OTHER FORMS OF INHERITANCE IN HUMANS?
  23. 32. Multiple Allelic Traits <ul><li>When a trait is controlled by multiple alleles, the gene exists in several allelic forms. </li></ul><ul><ul><li>ABO blood types </li></ul></ul><ul><ul><ul><ul><li>Phenotype Genotype </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>A I A I A ,I A i </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>B I B I B ,I B i </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>AB I A I B </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>O ii </li></ul></ul></ul></ul></ul>
  24. 36. LARGE NUMBER OF TRIPLET REPEATS OF CGG AT FRAGILE SITE ON X CHROMOSOME
  25. 37. 4. WHAT IS A PEDIGREE?
  26. 43. 5. HOW CAN GENETIC DISORDERS BE DETECTED?
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