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Genetics · Chapter 2: Mutations

Year 11 Science · About 15 minutes with activities · Turn your sound on

Chapter 2 · Mutations
A mutationa change in the base sequence
Same speciesslightly different DNA
Original allele
New allele
A → T
Normal red blood cell
Sickle cell
Cystic fibrosismutation in the CFTR gene
BRCA1 / BRCA2higher risk of some cancers

Chapter 2 recap

  • Genetic variation is the differences in the DNA of individuals within a species. Mutations are the only source of new alleles.
  • A mutation is a random, permanent change in the base sequence of DNA. Point mutations: substitution (base replaced), deletion (base removed), insertion (extra base added).
  • Deletions and insertions cause a frameshift: every triplet after the mutation changes. A substitution changes only one triplet. Examples: sickle cell anaemia, cystic fibrosis, BRCA1/BRCA2.
  • Next: Chapter 3 · Sexual reproduction and meiosis

Where do new alleles come from?

Chapter 2 · About 15 minutes · sound on

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