Name ___________________________
8.7 – Mutations
Key Concept: Mutations are changes in DNA that may or may not affect phenotype.
What are mutations?
 Changes in the _____________________________ of DNA
 May occur in ______________________ (aren’t passed to offspring)
 May occur in ________________ (eggs & sperm) and be passed to offspring
Are mutations helpful or harmful?
 Mutations happen _________________
 Almost all mutations are __________________
 __________________________ radiation cause mutations
 __________________ are anything in the environment that can cause mutations
 Many mutations are _________________ by enzymes
 Some types of ________________________________ result from _____________ mutations
 Some mutations may ____________ an organism’s ________________ (beneficial)
Type of Mutations
Chromosome Mutations
 May Involve:
 _________________________ of a chromosome
 ___________________ of part of the chromosome
 Five types exist
Deletion
 Due to ________________
 A _______________ of a chromosome is ____________
Inversion
 Chromosome segment ____________________
 Segment flips around ________________________
 Segment __________________
Duplication
 Occurs when a gene _________________________
Translocation
 Involves ____________________________ that aren‘t
homologous
 ___________ of one chromosome is
___________________________________ chromosomes
Nondisjunction
 ________________ of chromosomes
______________________ during meiosis
 Causes gamete to have ________________ or
___________________ chromosomes
 Can cause “______________”
(_________________ of the same chromosome
in an egg or sperm)
 Trisomy 21 (Down syndrome)
Gene Mutations
 Change in the _________________________________ of a __________
 May only involve a _______________________________
 May be due to _______________________________________________________________, etc.
Types of Gene Mutations
 Include:
 Point Mutations (Nonsense mutations)
 Substitutions
Similar to the chromosomal versions of
 Insertions
these mutations
 Deletions
 Inversions
 Frameshift
Point Mutations
 Change of a ___________ nucleotide
 Includes the deletion, insertion, or substitution of ____________ nucleotide in a gene
 __________________________ is the result of one nucleotide substitution
 Occurs in the ____________________________
Nonsense Mutation
 Type of point mutation
 Results in a ____________________________ and usually a ____________________________
Frameshift Mutation
 ___________________________________ one or more nucleotides
 Changes the “______________________” like changing a sentence
 ________________ built ___________________
 Original:
 The fat cat ate the wee rat.
 Frame Shift (“a” added):
 _________________________________________________
Silent Mutations
 Some mutations _________________________ and are called “silent”
 Example:
 GUC changed to GUG
 Both code for the amino acid valine
 This would ___________________________________ being made in any way
Mutations may or may not affect phenotype.
 ____________________________________ tend to have a big effect.
 Some _______________________________ change phenotype by:
o causing a premature stop codon.
o causing a change in protein shape or the active site.
o causing a change in gene regulation.
 Some gene mutations do not affect phenotype.
 A mutation may be silent because….
 It occurs in a ____________________________.
 It may not affect protein _______________ or the _____________________.