MUTATIONS
11.6 and 12.2
I.
General characteristics
 Are the result of changes in
DNA sequence
 Most are harmless, some are
bad, some are good
 Are usually caused by
mutagens
 Can occur in any cell
o If it occurs in a nonsex cell it
is a somatic mutation. Is this
inherited?
o If it occurs in a germ cell it is
a germ cell mutation. Is this
inherited?
 There are 2 groups of
mutations
o Gene mutations
o Chromosomal mutations
II. Gene Mutations
 A change in DNA structure due
to changes in the nucleotide
sequence of DNA
 Affect involves only 1 gene
 Types of gene mutations:
A. Point mutation (base
substitution)
 Only one nucleotide is
changed
 Possible effects:
o Silent mutation: change
in the nucleotide doesn’t
change the protein
sequence. Why?
o missense mutation:
change in the nucleotide
alters the amino acid
coded for
o nonsense mutation: a
codon that codes for an
amino acid is altered to a
stop codon
B. Frameshift mutation: a
nucleotide is deleted or
inserted altering the entire
protein
http://highered.mcgrawhill.com/sites/0072556781/student_vi
ew0/chapter11/animation_quiz_3.htm
l
http://highered.mcgrawhill.com/sites/0072556781/student_vi
ew0/chapter11/animation_quiz_4.htm
l
https://www.youtube.com/watch?v=k
p0esidDr-c
III. Chromosomal Mutations
A change in the structure or
number of chromosomes
A. Change in chromosome
structure
 Deletion mutation: part of a
chromosome is deleted
Ex: Fragile X syndrome
 Duplication mutation: part of a
chromosome is duplicated
 Inversion mutation: part of a
chromosome is inverted
 Translocation: part of one
chromosome is moved to
another. THIS IS NOT
CROSSOVER
http://highered.mcgrawhill.com/sites/0070960526/student_vi
ew0/chapter18/animation_quiz_1.htm
l
https://www.youtube.com/watch?v=F
gMKGIED4Yo
B. Change in chromosome
number
Nondisjunction:
 failure of homologous
chromosomes or sister
chromatids to separate
during meiosis
 results in an organism with
too few or too many
chromosomes
http://www.sumanasinc.com/webcon
tent/animations/content/mistakesmei
osis/mistakesmeiosis.swf