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Review your understanding of mutations in this free article aligned to NGSS standards.

Key points:

  • A mutation is any change to the nucleotide sequence of a DNA molecule. Some mutations arise as DNA is copied. Others are due to environmental factors.
  • A mutation in a gene can change the structure and function of the protein encoded by that gene. This, in turn, can affect an organism’s traits.
  • Mutations can be considered harmful, beneficial, or neutral to an organism.
    • Harmful mutations have negative effects on an organism’s health and survival. For example, some mutations cause inherited disorders such as sickle cell anemia and cystic fibrosis.
    • Beneficial mutations have positive effects on an organism’s health and survival. For example, some people have mutations that lower their risk of developing type 2 diabetes.
    • Neutral mutations have no observable effect on an organism’s traits. For example, some gene mutations do not lead to amino acid changes, and so do not affect protein function.
An image of red blood cells as viewed under a microscope. Normal red blood cells are shaped like round discs. In contrast, sickle-shaped red blood cells are elongated and pointy.
Normal (round) and sickle (long) red blood cells. Sickle cell anemia is caused by a gene mutation that affects red blood cells, causing them to be elongated and pointy. Image credit: “Sickle cells illustration" by NHLBI, Public Domain.

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