Title: Chapter 6: Chromosome Mutations
1Chapter 6 Chromosome Mutations
Chromosome mutations/aberrations
Variation in chromosome number aneuploidy eup
loidy polyploidy
2Nondisjunction
Homologous chromosomes during anaphase I
Sister chromatids during anaphase II
3Monosomy
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-)
4Trisomy
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
5Down syndrome, 47,21
6Polyploidy
1) Addition of one or more sets of chromosomes
(replication)
2) Combination of chromosome sets from different
species
7Polyploidy
Autopolyploidy
The benefits of autopolyploid breeding
increased size of plant organs- roots, leaves,
flowers fruits, seeds
8Polyploidy
Allopolyploidy
9Variations in Chromosome Structure
Deletions
10Variations in Chromosome Structure
Duplications
Due to unequal crossing over
11Evolution of hemoglobin genes
12Variations in Chromosome Structure
Inversions
Paracentric Pericentric
13Variations in Chromosome Structure
Translocation
14Variations in Chromosome Structure
Translocation unbalanced gametes are produced