Types of Gene Mutations to Know for General Biology II

Gene mutations are changes in the DNA sequence that can impact how proteins are made. Understanding these mutations, like point mutations, insertions, and deletions, helps us grasp their role in evolution, disease, and the diversity of life.

1. Point mutations

   • Involve a change in a single nucleotide base pair in the DNA sequence.
   • Can be classified as transitions (purine to purine or pyrimidine to pyrimidine) or transversions (purine to pyrimidine or vice versa).
   • May lead to changes in the amino acid sequence of proteins, potentially affecting their function.

2. Insertions

   • Occur when one or more nucleotide bases are added to the DNA sequence.
   • Can disrupt the reading frame of the gene, leading to altered protein synthesis.
   • May result in gain-of-function mutations or new traits in organisms.

3. Deletions

   • Involve the removal of one or more nucleotide bases from the DNA sequence.
   • Can also cause frameshift mutations, altering the downstream amino acid sequence.
   • Often lead to nonfunctional proteins or loss of gene function.

4. Frameshift mutations

   • Result from insertions or deletions that are not in multiples of three nucleotides.
   • Shift the reading frame of the genetic code, changing all subsequent amino acids.
   • Typically have severe effects on protein function and can lead to premature stop codons.

5. Missense mutations

   • Lead to the substitution of one amino acid for another in a protein.
   • Can be neutral, beneficial, or harmful depending on the properties of the substituted amino acid.
   • May affect protein structure and function, influencing traits and disease susceptibility.

6. Nonsense mutations

   • Convert a codon that codes for an amino acid into a stop codon.
   • Result in truncated proteins that are usually nonfunctional.
   • Often lead to severe genetic disorders or diseases.

7. Silent mutations

   • Change a nucleotide in the DNA sequence without altering the amino acid sequence of the protein.
   • Often occur in non-coding regions or in codons that code for the same amino acid (due to redundancy).
   • Generally have no phenotypic effect, but can influence gene expression or splicing.

8. Chromosomal translocations

   • Involve the rearrangement of parts between non-homologous chromosomes.
   • Can lead to gene fusion, creating hybrid genes that may have altered functions.
   • Associated with various cancers and genetic disorders.

9. Inversions

   • Occur when a segment of DNA is reversed within the chromosome.
   • Can disrupt gene function or regulatory elements, potentially leading to phenotypic changes.
   • May affect recombination during meiosis, influencing genetic diversity.

10. Duplications

    • Involve the copying of a segment of DNA, resulting in multiple copies of a gene or region.
    • Can lead to gene dosage effects, where increased gene product alters cellular function.
    • May contribute to evolution by providing raw material for new gene functions.