Download Point Mutations

Welcome 1/26-27/16
 In your journal, write a paragraph explain what a genetic
code is and the purpose of transcription and translation.
 Turn in Snork DNA and Vocab
 Notes on Mutations
 Mutations Practice problems
 Homefun: study for your quiz
 Reminder: Next Monday and Tuesday project is due!
Mutations
Learning Objectives
 Define mutations and describe the different types of
mutations.
 Describe the effects mutations can have on genes.
Mutations
Mutations are heritable changes in genetic information.
Types of Mutations
Mutations fall into two basic categories:
 Gene mutations
 Chromosomal mutations
Gene Mutations: Point Mutations
A point mutation is a change in a single nucleotide.
There are three types of point mutations:
Point Mutations: Substitutions
In a substitution, one base is changed to a different base.
Point Mutations: Insertions and Deletions
Insertion mutation: when a
single extra base is added into
the code
Deletion mutation: when a single
base is removed from the code
Point Mutations vs.
Frameshift Mutations
• The substitution example was a point
mutation.
• These last two examples of deletion and
insertion were frameshift mutations.
• What’s the difference between a point
mutation and frameshift mutation?
• Which has the most significant impact on the
protein? Why?
Synonymous (“Silent”) Point
Mutations
• What do you think a synonymous (“silent”) point mutation is?
– Do not cause a change in the amino acid sequence
– Generally, do not cause a change in the protein—
however, can reduce the amount of a specific protein the
cell makes or cause the structure of the protein to be
changed in a manner that disrupts its functioning in the
body
• Example:
– TAT changed to TAC—both still code from Tyrosine
– CTC changed to CTA—both still code for Leucine
Chromosomal Mutations
 Deletion
 Duplication
 Inversion
 Translocation
Chromosomal Mutations
• What changed?
• How would this type of
change affect the protein?
Chromosomal Mutations
• What changed?
• How would this type of
change affect the protein?
Chromosomal Mutations
• What changed?
• How would this
type of change
affect the protein?
Non-Disjunction
Ex: Trisomy 21 or Down Syndrome
• Sometimes, there is an
error in meiosis when
egg or sperm cells
divide resulting in too
many or too few
chromosomes.
• How do you think this
type of change would
impact an organism?
Mutation Impact
• The impact of a mutation on an individual also
depends on where and when it occurs.
• If there was a mutation in the DNA of a zygote, how
would that impact the individual?
• How might a mutation in a skin cell affect an
individual?
Effects of Mutations
Mutations can harm, help, or
have no effect on an organism.
Some mutations arise from
mutagens—chemical or
physical agents in the
environment.
Effects of Mutations: Harmful
Some of the most harmful mutations are those that dramatically
change protein structure or gene activity.
Example: Sickle cell
disease affects the
shape of red blood cells.
Sickle cell
Normal red blood cell
Effects of Mutations: Beneficial
Mutations often produce proteins with new or altered functions
that can be useful to organisms in different or changing
environments.
Example: The fruit of the
Tahiti lime is seedless, a
result of polyploidy.