BRAINCAKEChromosome Mutation
A chromosome mutation is a change in the structure or number of whole chromosomes, as opposed to a gene (point) mutation, which changes the base sequence of a single gene. Chromosome mutations can happen spontaneously, often during crossing over in meiosis, and their rate is increased by mutagens such as ionising radiation.
Changes in structure occur when chromosomes break and rejoin incorrectly:
• Deletion: a section of chromosome is lost, along with the genes on it.
• Duplication: a section is repeated, so the genes on it are present in extra copies.
• Inversion: a section breaks off, turns through 180° and rejoins, so its genes are in reverse order.
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Key terms in this lesson
- non-disjunction
- The failure of chromosomes or chromatids to separate correctly during meiosis, producing gametes with an abnormal chromosome number.
More in Meiosis and Sexual Reproduction
- Anaphase 1
- Telophase 1
- Meiosis 2
- The Importance of Meiosis
- Non-disjunction
- Down's Syndrome
- Turner's Syndrome
- Spermatogenesis
All 28 lessons in Meiosis and Sexual Reproduction · All Edexcel AS-level Biology topics