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How can defective proteins and enzymes lead to genetic disease symptoms?
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human genetic disease
Photomicrograph of the BRCA2 tumor suppressor gene on chromosome 13 of the human genome. Inactivation of this growth-regulating gene is associated with a higher risk of developing breast cancer.
Genetic diseases often arise from mutations in DNA that lead to the synthesis of defective or absent proteins and enzymes. These molecular errors disrupt essential cellular functions, manifesting as clinical symptoms through several primary mechanisms:
- Metabolic Blockage: When an enzyme is missing or inactive, the metabolic pathway it catalyzes becomes blocked. This prevents the formation of necessary end products and can cause the toxic accumulation of intermediate substrates.1
- Loss of Function: Mutations such as nonsense or frameshift mutations may result in the complete absence of a protein. If the protein is a critical enzyme, the resulting deficiency can have severe or fatal consequences, such as in inborn errors of metabolism.123
- Protein Misfolding: Mutations can cause proteins to assume incorrect three-dimensional shapes. The accumulation of these misfolded proteins within the rough endoplasmic reticulum triggers cellular stress, leading to dysfunction and cell death, as seen in certain inherited skeletal disorders.4
- Toxic Gain of Function: In some cases, mutant proteins may retain catalytic activity but cause damage through other means, such as the formation of toxic byproducts or the disruption of cellular defense systems, as observed in specific forms of amyotrophic lateral sclerosis.5