Human Genetics I
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Human Genetics I

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Human Genetics I Human Genetics I Presentation Transcript

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