Nursing 280: Pathophysiology Examination

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Nursing 280 PathophysiologyExamination 2
Module ISection D Disorders of Genetic
Expression

• Presented by
• Ronda M. Overdiek M.S.N., R.N.

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Section DDisorders of Genetic Expression

• Review
• Chapter 1
• Objective 1 (Cell Cycle)
• Chapter 2
• Objective 1 (Chromosomes)

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Objective 2 Chromosomal aberration

• Deletion
• Loss of a segment within one chromosome arm
• Caused by broken chromosomes and lost DNA
• Duplication
• Repetition of a segment of a chromosome arm

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Objective 2 Chromosomal aberration

• Inversion
• Occurrence of two breaks on a chromosome,
  followed by reinsertion of a missing fragment at
  its original site but in inverted order.
• Translocation
• Interchanging of genetic material between
  nonhomologous chromosomes.

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Objective 2Modes of Inheritance

• Phenotype
• Outward appearance of an individual, which is the
  result of both genotype and environment
• Genotype
• Composition of genes at a given locus.

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Objective 2Modes of Inheritance

• Dominance
• Effects of the allele that are observable
• Recessive
• Effects of the allele that are hidden

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Objective 2Modes of Inheritance

• Penetrance
• The percentage of individuals with a specific
  genotype who also exhibit the expected phenotype
• Expressivity
• The extent of variation in phenotype associated
  with a particular genotype.

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Objective 2X-Linked

• Sex-linked
• Caused by genes located on the sex chromosomes.
• Most are X-linked recessive
• Males are affected more
• Single copy of X-linked recessive gene
• Two copies are needed for females
• Females are carriers
• Example Hemophilia

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Objective 3Describe defects of autosomal
chromosomes

• Definitions
• Aneuploidy Somatic cell that does not contain a
  multiple of 23 chromosomes.
• Trisomic A cell containing three copies of one
  chromosome
• Monosomy The presence of only one copy of a
  given chromosome in a diploid cell.

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Objective 3Describe defects of autosomal
chromosomes

• Trisomy 21 (Downs Syndrome)
• Common cause is nondisjunction
• Phenotypes
• Mental retardation, broad flat face, short
  stature, short hands with a crease across the
  middle, large, wrinkled tongue.

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Objective 4Describe defects of sex chromosomes

• Turners Syndrome
• Presence of a single X chromosome and no
  homologous X or Y chromosome. Total 45
• Phenotype
• Short stature, female genitalia, webbed neck,
  shieldlike chest, sterile.
• Incidence 15,000 births

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Objective 4Describe defects of sex chromosomes

• Klinefelter Syndrome
• Combination of XXY
• Sex chromosome trisomic
• Phenotype
• Testicular atrophy, lanky build, mentally
  retarded, sterile, breast development, etc.

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Downs/Turner/Klinefelter Syndromes

• Table 2-1 Page 45

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Why?

• Patient Population
• Pharmacological Interventions
• Genetic Counseling