type of mutation mechanism frequency per cell division

point mutation
1. mistakes in DNA replication
2. DNA damage by chemical mutagens (or by radiation) and misrepair
~10-10/basepair
~10-5/gene
~0.5/cell

submicroscopic deletion or insertion
1. unequal crossing over
2. misalignment during DNA replication
3. insertion of mobile element
4. DNA damage by chemical mutagens (or by radiation) and misrepair
included in the above

microscopically visible deletion, translocation or inversion
1. unequal crossing over
2. DNA damage by chemical mutagens (or by radiation) and misrepair
6 x 10-4

extra, missing, broken chromosomes
missegregation at meiosis 1 in 100
BASED ON: www.ucl.ac.uk/~ucbhjow/b241/mutation.html and gened.emc.maricopa.edu/Bio/BIO181/BIOBK/Crossover.gif


Autosomal Chromosome Mutations

Patau syndrome Three Copies of Chromosome 13
Edwards syndrome Three Copies of Chromosome 18
Down syndrome Three Copies of Chromosome 21
Cri-du-chat syndrome Deletion of part of Chromosome 5
Abnormalities in Sex Chromosomes



Sex Chromosome Abnormalities

# ChromsFormSyndromeGenderFrequency
46XXNormalFemale51.1%
46XYNormalMale48.9%
45Y0lethallethal0
45XOTurner SyndromeFemale1/5,000
47XYYJacobs SyndromeMale1/300
47XXYKlinefelter's SyndromeMale1/700
47XXXTriplo XFemale1/4000