MODULE 6: MUTATIONS AND ALLELES

• Alteration in DNA sequence, including single base pair substitutions, insertions, deletions, or major chromosome structural changes.

  Mutation
• Single base-pair substitution.


  Point mutation
• Addition of one or more base pairs.

  Insertion
• Removal of one or more base pairs.

  Deletion
• Structural changes affecting whole chromosomes.

  Chromosome alteration
• Mutation locations that Impact protein structure and function.

  Coding regions
• Mutation locations that Include introns and regulatory sequences, affecting gene expression.

  noncoding regions
• Mutations may or may not lead to observable changes in the organism's traits.

  Variable impact
• Impact depends on where the mutation occurs and its effect on gene function or regulation.

  Dependence on Mutation Type and Cell Type:
• Heritable, passed on to offspring, affecting genetic diversity and potentially causing genetic diseases.

  germ cell or sex cells
• Not heritable, may lead to altered cell function or tumors within the individual.

  Somatic cell mutations
• Occur without known external cause, often during normal biological processes like DNA replication.

  Spontaneous mutations
• Result from external factors, natural or artificial agents.


  induced mutations
• induced mutations were First demonstrated in _____ by _____ with X-rays on _____, and in ____ by _____ on _____.

  1927, Muller, Drosophila, 1928, Stadler, barley
• Extremely low across all organisms. Varies significantly between species and even within the same species and among different genes

  Spontaneous mutation rate
• Viral and bacterial genes: Approximately ___ in _____ replications.

  1, 100 million
• Maize, Drosophila, humans: Higher rates, ranging from ___ in ____ to __ in ___ mutations per gamete.

  1, 1 million, 1, 100 00
• Some mouse genes: Even higher rates, 1 in ____ to 1 in ____

  100 000, 10 000
• Point mutations alter a single nucleotide base, leading to missense, nonsense, or silent mutations depending on their effect on protein synthesis.


  base-pair changes
• These mutations can disrupt the reading frame of a gene, leading to frameshift mutations and potentially truncated or non-functional proteins.

  Insertions and deletions
• These mutations involve expansions of repetitive DNA sequences within genes, leading to disorders such as Huntington disease and various types of ataxias.

  Expanded DNA repeats