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Chapter 17.7 Point mutations can affect
protein structure and function
What we are learning today!
Mutations in the DNA sequence of a
gene may or may not affect the
expression of the gene or the sequence
of amino acids in an encoded protein
 In other words,

 MUTATIONS are BAD for us & GOOD for us
Pink dolphins in the Amazon
Mutant Fruit Flies
Mutant Frog
Human Phalangial Polydactyly
Trisomy 21
POP QUIZ
What is a chromosomal mutation?
2. When does chromosomal mutation
occur? (hint mitosis/meiosis)
3. Definition of Aneuploidy &
Polyploidy?
4. Definition of Monosomic & Trisomic?
5. Definition of Deletion & Duplication?
6. Define inversion & translocation?
1.
Chromosomal mutation
Occur during
meiosis causing
either a change in
the chromosome
number or an
alteration of a
chromosome.
Nondisjunction
• pair of homologous
chromosomes don’t move
apart
•Aneuploidy: Xtra copy or
one less copy
•Trisomic: Chromosome
in triplicate (nonlethal)
•Monosomic:
Chromosome missing
(always lethal)
•Polyploidy: more than 2
complete chromosome
sets in a cell
Alteration of Chromosome
Cri-du-Chat <kree doo shah>
Gene Mutation: pg: 328-330
 Mutation:
Change in the genetic
material of a cell
 Occur on DNA/RNA levels that
causes changes in proteins
 2 main types:
 Point mutations: Chemical changes in just
one base pair of a gene
 Frameshift mutations: Number of
nucleotides added or deleted not a multiple of
3; cause improper grouping of codons
Point Mutations
 Substitution:
replacement of one
nucleotide pair
 Silent mutation: doesn’t affect
encoding of protein
 Missense mutation: still encodes of
an amino acid but it may not be the
right one.
 Nonsense mutation: creates a stop
codon
Sickle Cell Anemia
The genetic
disorder is
due to the
mutation of
a single
nucleotide,
from a GAG
to GTG
codon
mutation.
Frameshift Mutations
 Insertions:
addition of one or
more nucleotides
 Deletion: removal of one or
more nucleotides
Mutagens

Physical and chemical agents that
interact with DNA in ways that cause
mutations
Take Home Message
 Mutations
can be:
 GOOD:
○ Genetic Variations &
phenotype differences
 BAD:
○ Cause disease, sickness,
or death
Activity
Number 1
5’TGGAGCCTTCTGATGCCTAACGTACGT3’
Number 2
5’TGCTCGCTCCTAATACCAGAGGTGCGG3’