Chromosome Mutations Definitions A mutation is any change in the DNA. A chromosome mutation is a change in the structure or arrangement of the chromosomes w Numerical Changes
{ Euploidy -- Excess or Defficiency in the number of the entire chromomosomal complement. { Aneuploidy -- Excess or Defficiency in a single chromosome. w Structural Changes Numerical Chromosome Mutations Euploid -- “True Number” The cell(s) have the same number of copies of all the chromosome. 1. Monoploid (Haploid if a gamete) 2. Diploid (Often is not considered a Euploid) 3. Triploid 4. Tetraploid Euploidy
Chromosomes shown at metaphase
Normal
Diploid
Euploid
Monoploid
Triploid
Tetraploid
Euploidy is an excess or deficiency for the entire complement of chromosomes. Euploidy Organisms w Plants, amphibians, lower reptiles w Some cells in other organisms (liver, midgut, etc.)
Root Causes w Nondisjunction w Autoreduplication Euploidy
(continued) Origins w Autopolyploidy
{ Often involving individuals within the same species. { Infertile. Propagation by cloning. w Allopolyploidy
{ Often involving individuals from different species. { Fertile. Dosage Concerns Examples Numerical Chromosome Mutations Aneuploidy Excess or Defficiency in a single chromosome. 1. Monosomy 2. Disomy (only if normally cell is not diploid) 3. Trisomy 4. Tetrasomy Aneuploidy
Chromosomes shown at metaphase
Normal
Diploid
Aneuploid
Monosomic
Trisomic
Tetrasomic
Aneuploidy is an excess or deficiency for fewer than the entire complement of chromosomes. Aneuploidy Organisms w All organisms w Variability in how they deal with it
Root Causes w Nondisjunction w Results of Chromosome Structure Mutations Aneuploidy -- Examples Plants w Jimson Weed (Datura stramonium)
Animals w Drosophila: Triploid females are viable & fertile. Trisomy flies are not! w Human (autosomal):
{ Trisomy 13 (Patau Syndrome) 1:20,000 { Trisomy 18 (Edwards Syndrome) 1:10,000 { Trisomy 21 (Down Syndrome) 1:700 { Other rare ones (7, 9, 12, 14, & 22) Aneuploidy Examples w Human Sex Determining Chromosomes
1. Monosomy { 45,X (Turner Syndrome) 1:2000 female births 2. Trisomy { 47,XXX (Triplo-X) 1:1200 female births { 47,XYY 1:1000 male births { 47,XXY (Klinefelter Syndrome) 1:800 male births 3. Tetrasomy & above { Klinefelter Syndrome 48,XXXY & 49,XXXXY { 48,XXXX & 49,XXXXX