Lecture on Mutations and Protein Structure

Introduction to Mutations

• Mutations are the ultimate source of new genes.
• They involve changes in the sequence of nucleotides in DNA.

Types of Mutations

Point Mutations

• Involves a change in a single nucleotide pair within a gene.
• Example: Sickle-cell disease
  • Caused by a change in a single nucleotide pair.
  • Results in substitution of glutamic acid with valine.
  • Causes malfunction in hemoglobin protein in red blood cells.

Small-Scale Mutations

• Insertions and Deletions
  • Addition or loss of nucleotide pairs.
  • Often result in disastrous effects.
  • Can cause frameshift mutations.
    • Occurs when the number of nucleotides inserted or removed is not a multiple of three.
    • Alters the organization of codons and changes the resulting protein.

Causes of Mutations

• Mutagens: Physical and chemical agents interacting with DNA.

Types of Mutations Caused by Mutagens

Silent Mutations

• Change in nucleotide pair has no effect on the encoded protein.
• Results in the same amino acid being produced.
• No visible effect on phenotype or protein function.

Missense Mutations

• Change in nucleotide sequence results in the substitution of one amino acid for another.
• Impact depends on the characteristics of the replaced amino acids.

Nonsense Mutations

• Nucleotide substitution changes a codon into a stop codon.
• Prematurely stops protein translation, resulting in a truncated protein.
• Truncated proteins are often nonfunctional.

Conclusion

• Understanding mutations is crucial for studying gene function and protein synthesis.
• Further resources and tutoring are available for Baylor students at the SID Richardson building.

Additional Resources

• Images and content from Campbell Biology's 11th Edition.
• Free tutoring available for enrolled Baylor students. Visit www.ajustlock.com for more details.