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Chapter 6: Chromosome Mutations

Chapter 6: Chromosome Mutations. *Chromosome mutations/aberrations. Variation in chromosome number: *aneuploidy *euploidy *polyploidy. Nondisjunction. Homologous chromosomes: during anaphase I. Sister chromatids: during anaphase II. Monosomy.

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Chapter 6: Chromosome Mutations

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  1. Chapter 6: Chromosome Mutations *Chromosome mutations/aberrations Variation in chromosome number: *aneuploidy *euploidy *polyploidy

  2. Nondisjunction Homologous chromosomes: during anaphase I Sister chromatids: during anaphase II

  3. Monosomy *Condition in which one member of a chromosome pair is missing (2n-1) In Drosophila: Haplo-IV are monosomic for chromosome 4 *develop more slowly, reduced size, impaired viability In Plants: Maize, tobacco, evening primrose, Jimson weed *Segmental deletions *Cri-du-chat (46,5p-)

  4. Trisomy *Condition in which one chromosome is present in three copies (2n+1) In Plants: Jimson weed, rice In Drosophila and humans: Has severe effects, usually lethal Exceptions: Patau syndrome, 47,13+ Edwards syndrome, 47,18+

  5. Down syndrome, 47,21+

  6. Polyploidy 1) Addition of one or more sets of chromosomes (replication) 2) Combination of chromosome sets from different species

  7. Arise in several ways: *failure of all chromosomes to segregate during meiosis *two sperm may fertilize an ovum *experimentation Polyploidy Autopolyploidy The benefits of autopolyploid breeding: increased size of plant organs- roots, leaves, flowers fruits, seeds

  8. Polyploidy Allopolyploidy

  9. Variations in Chromosome Structure Deletions

  10. Crossover: A A A A A A A B B B B B B B C C C C C C C D D D D D D D A B C D A B C D A B C D A B C D A B C D Variations in Chromosome Structure Duplications Due to unequal crossing over:

  11. Evolution of hemoglobin genes

  12. Variations in Chromosome Structure Inversions *Paracentric *Pericentric

  13. Variations in Chromosome Structure Translocation

  14. Variations in Chromosome Structure Translocation – unbalanced gametes are produced

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