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Chapter 12 human genetics

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  • 1. Chapter 12- Human Genetics
  • 2. I. Human Heredity
    • A. Human chromosomes
    •  
    • 1. A picture of chromosomes arranged in a picture is called a karyotype.
  • 3.
  • 4.
    • 2. A normal human has 46 chromosomes, 23 pairs.
    • 3. The number of chromosomes helps identify what the organism is.
    •  
    • 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.
  • 5.
    • 5. All other cells have 46 chromosomes in them, they are diploid. These cells are called autosomes.
    •  
    • 6. All human egg cells carry a single X chromosome.
  • 6.
    • 7. Half of all sperm cells carry an X and half carry a Y chromosome.
    •  
    • 8. This ensures that just about half of the zygotes will be 46XX and the other half will be 46XY.
  • 7.
  • 8. B. Human Traits
    • 1. Human genes are inherited according to the same principals that Mendel discovered.
    •  
    • 2. A pedigree chart shows relationships within a family.
  • 9.
  • 10.
    • 3. Genetic counselors analyze pedigree charts to infer the genotypes of family members.
    •  
    • 4. Many traits are strongly influenced by environmental, or non-genetic factors, including nutrition and exercise.
  • 11. C. Human Genes
    • 1. The human genome- our complete set of genetic information includes tens of thousands of genes.
    •  
    • 2. Some of the very first genes to be identified were those that control blood type.
  • 12. D. Blood Group Genes
    • 1. Human blood comes in a variety of genetically determined blood groups.
    •  
    • 2. The different blood types are A, B, AB O plus there is a Rh+ or Rh- factor.
  • 13. BLOOD GROUPS
    • Phenotype Genotype Antigen Antibodies
    • A I A I A or I A I o A B
    • B I B I B or I B I o B A
    • AB I A I B A and B -------
    • O I o I o -------- A and B
  • 14. E. Recessive Alleles
    • 1. Many human genes have become known through the study of genetic disorders.
    •  
    • 2. In most cases genetic disorders are USUALLY recessive.
    •  
    • 3. See page 345 to see some disorders
  • 15. Albinism
  • 16. Cystic Fibrosis
  • 17. Dwarfism
  • 18. Sickle Cell Disease
  • 19. F. Dominant Alleles
    • 1. Not all genetic disorders are caused by a recessive allele.
    •  
    • 2. Two examples of a genetic disorder caused by autosomal dominant alleles are dwarfism and Huntington ’ s disease.
  • 20. Huntington’s disease
  • 21. G. Codominant alleles
    • 1. Sickle cell disease is caused by a codominant allele.
  • 22. H. From Gene to molecule
    • 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.
    •  
    • 2. CF is most common among people with Northern Europe ancestors.
  • 23.
    • 3. People with CF have serious digestive problems in addition they produce thick, heavy mucus that clogs their lungs and breathing passageways.
    •  
    • 4. Sickle cell is a disease found in African American ’ s.
  • 24.
    • 3. It is a bent and twisted shape of the RBC ’ s.
    •  
    • 4.   As a result, blood stops moving through these vessels, damaging cells, tissues and organs.
    •  
    • 5. Sickle cell disease produces physical weakness, and damage to the brain, heart, and spleen.
  • 25. II. Human Chromosomes
    • A. Human Genes and Chromosomes
    • 1. Chromosomes 21 and 22 are the smallest human autosomes. Chromosome 22 contains 43 million DNA base pairs! Chromsomes 21 contains about 32 million!
    •  
    • 2. MILLIONS of base pairs!
  • 26. B. Sex Linked Genes
    • 1. Many sex-linked genes are found on the X chromosomes. More than 100 sex-linked genetic disorders are found on the X.
    •  
    • 2. Males have just one X chromosome, thus all X-linked alleles are expressed in males even if they are recessive.
  • 27.
    • 3. Some sex-linked disorders are colorblindness, hemophilia, and Duchenne muscular dystrophy.
  • 28. C. Color Blindness
    • 1. The most common disorder is red-green colorblindness affecting 1 in 10 males in the US.
    •  
    • 2. Among females colorblindness is only 1-100.
  • 29.
  • 30.
  • 31.
  • 32.
  • 33. D. Hemophilia
    • 1. Two important genes carried on the X chromosome help blood to clot.
    •  
    • 2. In hemophilia, a protein necessary for normal blood clotting is missing.
    •  
    • 3. About 1 in 10,000 males is born with hemophilia.
  • 34.
  • 35. E. Duschenne Muscular dystrophy
    • 1. This is a disorder that results in the progressive weakening and loss of skeletal muscles.
    •  
    • 2. In the US 1 out of 3000 males are born with this.
  • 36.
  • 37. F. X-Chromosome Inactivation
    • 1. Females have 2 X chromosomes, but males have only 1.
    •  
    • 2. In female cells, one X chromosome is randomly switched off.
  • 38. G. Chromosomal disorders
    • 1. The most common error in meiosis occurs when homologous chromosomes fail to separate. This is known as nondisjunction.
    •  
    • 2. If nondisjunction occurs, abnormal numbers of chromosomes may find their way into gametes, and a disorder of chromosome numbers may result.
  • 39.
    • 3. IF two copies of an autosomal chromosome fail to separate during meiosis, an individual may be born with three copies of a chromosome.
    •  
    • 4. This is known as trisomy
  • 40.
    • 5. The most common trisomy is down syndrome- having an extra chromosome on pair number 21.
    •  
    • 6. 1-800 babies are born with Down syndrome.
  • 41.
  • 42.
    • 7. Disorders also occur among the sex chromosomes. Two of these are Turner syndrome and Klienefelter ’ s.
    •  
    • 8. In Turner syndrome there is only 1 X. The female is sterile and their sex organs do not develop at puberty.
  • 43.
    • 9. In males, Klinefelter ’ s has an extra X, XXY, XXXY or even XXXXY.
  • 44.
    • 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.
  • 45. III. Human Molecular Genetics
    • A. Human DNA analysis
    •  
    • 1. DNA fingerprinting is used by molecular biology to identify individuals.
  • 46.
    • 2. The human genome project is an ongoing effort to analyze the human DNA sequence.
    •  
    • 3. In gene therapy, an absent or faulty gene is replaced by a normal, working gene.
  • 47.
    • 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?
  • 48. The END