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An Evidence Framework for Genetic Testing (2017) / Chapter Skim
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Appendix A: Understanding Genetic Variance and Phenotype Expression
Pages 89-94

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From page 89...
... A missense mutation is the replacement of one base with another that can cause disease if the variant results in the substitution of a different amino acid in the resulting protein and a consequent change in function. A nonsense mutation changes one base of a three-base codon for an amino acid to a premature stop codon and results in a truncated and usually nonfunctional protein.
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From page 90...
... Variants occur as cells multiply and tissues grow, especially in highly proliferative tissues, such as intestinal epithelia, providing a selective growth advantage to mutant cells. Variants that affect cellular proliferation, survival, or invasive potential can cause cells to multiply uncontrollably to form a neoplasm.
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From page 91...
... Semidominant and incompletely dominant are used to describe a situation in which heterozygotes have an abnormal phenotype but the phenotype is less severe than the phenotype expressed in homozygotes. In codominant inheritance, two alleles of a gene are expressed, and each version makes a slightly different protein with the potential to have a measurable influence on the genetic trait or to determine the characteristics of the genetic condition (e.g., ABO blood group)
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From page 92...
... Mitochondrial Mitochondrial inheritance is a form of strict maternal inheritance. It applies to genes in mitochondrial DNA that do not demonstrate typical patterns of Mendelian inheritance.
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From page 93...
... . In some cases, a parent who carries a chromosomal abnormality can have a normal balance of genes and show no abnormal phenotype, but genetic recombination or chromosome segregation in that parent's germline generates gametes that have unbalanced complements of genes and thereby causes problems for the progeny.
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Key Terms

  • x chromosome
  • autosomal dominant
  • autosomal recessive
  • chromosomal disorders
  • recessive diseases

  • acid sequence
  • colorectal cancer
  • encoded amino
  • frameshift mutation
  • reduced penetrance

  • protein function
  • cause disease
  • specific amino
  • pathogenic variants
  • involve genes

  • germline cells
  • genetic variant
  • mendelian inheritance
  • disorders occur
  • genes found

  • spinal cord
  • individual genes
  • diseases include
  • neither chromosome
  • nonfunctional protein

  • mitochondrial dna
  • protein changes
  • mutant protein
  • diseases reflect
  • marfan syndrome


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