Chapter 6: Chromosome Mutations

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Chapter 6 Chromosome Mutations
Chromosome mutations/aberrations
Variation in chromosome number aneuploidy eup
loidy polyploidy
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Nondisjunction
Homologous chromosomes during anaphase I
Sister chromatids during anaphase II
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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-)
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Trisomy
Condition in which one chromosome is present in
three copies (2n1)
In Plants Jimson weed, rice
In Drosophila and humans Has severe effects,
usually lethal
Exceptions
Patau syndrome, 47,13
Edwards syndrome, 47,18
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Down syndrome, 47,21
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Polyploidy
1) Addition of one or more sets of chromosomes
(replication)
2) Combination of chromosome sets from different
species
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Polyploidy
Autopolyploidy
The benefits of autopolyploid breeding
increased size of plant organs- roots, leaves,
flowers fruits, seeds
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Polyploidy
Allopolyploidy
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Variations in Chromosome Structure
Deletions
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Variations in Chromosome Structure
Duplications
Due to unequal crossing over
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Evolution of hemoglobin genes
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Variations in Chromosome Structure
Inversions
Paracentric Pericentric
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Variations in Chromosome Structure
Translocation
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Variations in Chromosome Structure
Translocation unbalanced gametes are produced