Genetic
Mutations
Standards:
• CLE 3210.4.6 Describe the connection
between mutations and human genetic
disorders.
Objectives:
• Investigate the affect of mutations on protein
production
• Differentiate between point mutations and
chromosomal mutations.
Gene Mutations Activity
• Complete the worksheet
What is a gene mutation?
• Mutations are changes in genetic
material – changes in DNA code –
which means changes in a gene(s)
• In gene mutations, the DNA code
will have one or more bases
missing, added, or exchanged in a
codon.
How common are mutations?
• Mutations occurs at a
frequency of about 1 in every
1 billion base pairs
• Everybody has about 6
mutations in each cell in their
body!
Does that mean I have a chance to
become a super hero/villian?
If I have that many mutations, why
don’t I look weird?
• Mutations are not always seen. The
affected gene may still function.
• Mutations may be harmful.
• Mutations may be beneficial.
• Mutations may have no effect on the
organism.
How do mutations
affect a population?
• Mutations are a major
source of genetic
variation in a
population increasing
biodiversity.
• Some variations may
help them to survive
better.
Beneficial or Harmful?
How are mutations inherited?
Only mutations that occur in gametes,
or were present when the organism
was fertilized, are passed onto
offspring.
Mutations that occur in body cells
(somatic cells) (after an organism has
developed) only affect the organism in
which they occur and are not passed
on.
Types of Gene Mutations
• Point mutation occurs when the base
sequence of a codon is changed. (ex.
GCA is changed to GAA)
• Chromosome mutations - Changes in
the number or structure of
chromosomes
Types of Point Mutations
• Point mutation occurs when the base
sequence of a codon is changed. (ex.
GCA is changed to GAA)
• There are 3 types:
•Substitution
•Deletion
•Insertion
Also called
frameshift
mutations
Substitution Mutations
Normal DNA: CGA – TGC – ATC
Alanine – Threonine - stop
Mutated DNA: CGA – TGC – TTC
Alanine – Threonine - Lysine
What
This
What
Theis
has
will
adenine
a substitution
happened
happen
wastoto
replaced
the the
amino
mutation
with
DNA?
acids?
thymine
Substitution Mutations
• This is a substitution mutation.
• A single nitrogen base is substituted
for another in a codon.
• It may or may not affect the amino
acid or protein.
Normal DNA:
CGA – TGC – ATC
Alanine – Threonine - stop
Mutated DNA: CGA – TGC – TTC
Alanine – Threonine - Lysine
TRY THIS!
• On your note paper write:
The cat ate the rat
• Change one letter in the sentence to represent a
substitution mutation.
Think – Pair - Share
• Why are we using 3 letter words?
• Share with your partner the substitution
change that you made
• Can you still “read” your sentence fairly easily?
• How damaging is a substitution mutation?
Analogy
The cat ate the rat.
SUBSTITUTION #1
Thc cat ate the rat.
May have little effect. You can still get the overall
idea. Like a typo on a test.
SUBSTITUTION #2
The hat ate the rat.
Changes the thought of the sentence.
The effect of the mutation depends on where the
substitution happens
Insertion Mutations
Normal DNA:
CGA – TGC – ATC
Alanine – Threonine – stop
Mutated DNA: CGA – TAG – CAT – C
Alanine – Isoleucine – Valine
An
This
adenine
is
an
was
insertion
inserted
What
What
will
has
happen
happened
to the
mutation,
thereby
pushing
also
a type
all the
of
amino
to the
acids?
DNA?
other
frameshift
bases over
mutation.
a frame.
Insertion Mutations
• This is an insertion mutation.
• A nitrogen base is inserted/added to the
sequence.
• It causes the triplet “frames” to shift.
• It always affects the amino acids and,
consequently, the protein.
Normal DNA: CGA – TGC – ATC
Alanine – Threonine - stop
Mutated DNA: CGA – TAG – CAT – C
Alanine – Leucine - Valine
Think – pair - share
• Predict the effect an insertion mutation cause
to our sentence:
THE CAT ATE THE RAT
•Remember: the sentence must remain with 3letter words (codons)
TRY THIS!
• On your notebook paper write:
The cat ate the rat.
• Insert a letter into any word above.
• Rewrite the sentence . Each word must have
only 3 letters to represent the codon.
• What were the effects of the insertion?
Analogy
The cat ate the rat.
Insertion
The cca tat eth era t.
Inserting the c causes a
FRAMESHIFT
THE SENTENCE NO LONGER
MAKES SENSE!!
Think – pair - share
• Where in the gene sequence would an
insertion mutation cause the most damage to
the DNA code?
• In the beginning, middle or end? Why?
At the beginning of the gene sequence – it
changes all the following codons, thus changing
all the amino acids.
Let’s examine the effect of location
THE CAT ATE THE RAT
INSERTION #1
– THE CAT ATE THA ERA T
– Would any of the codons code correctly?
INSERTION #2
– TAH ECA TAT ETH ERA T
– Would any of these codons code correctly?
Deletion Mutations
Normal DNA: CGA – TGC – ATC
Alanine – Threonine – stop
Mutated DNA: CGA – TCA- TC
Alanine – Serine
This
What
A What
guanine
iswill
called
has
happen
was
happened
a deleted,
deletion
to the
mutation,
thereby
amino
to the
pushing
also
acids?
DNA?
a type
all the
of
bases
frameshift
downmutation.
a frame.
Deletion Mutations
• This is a deletion mutation.
• A nitrogen base is deleted/removed from
the sequence.
• It causes the triplet “frames” to shift.
• It always affects the amino acids and,
consequently, the protein.
Normal DNA: CGA – TGC – ATC
Alanine – Threonine – stop
Mutated DNA: CGA – TCA- TC
Alanine – Serine
TRY THIS!
• Write the sentence on your paper:
The cat ate the rat.
• Delete one letter from any word.
• Rewrite the sentence. Remember:
each word can only have 3 letters.
Analogy
DELETION
The cat ate the rat.
Thc ata tet her at
FRAMESHIFT
The sentence no longer makes
sense!! Deletions can have huge
effects.
Standards:
• CLE 3210.4.6 Describe the connection
between mutations and human genetic
disorders.
Objectives:
• Investigate the affect of mutations on protein
production
• Differentiate between point mutations and
chromosomal mutations.
Think – pair - share
• Which type of mutation would have the
least damaging affect on an organism?
Normal DNA: CGA – TGC – ATC
Alanine – Threonine - stop
Mutated DNA: CGA – TGC – ATT
Alanine – Threonine - stop
Mutated DNA: CGA – TGC – ATG
Alanine – Threonine - Tyrosine
• Substitution has the least affect because
it changes only one amino acid or it may
change no amino acid.
An example of a substitution mutation is sickle
cell anemia
• Only one codon in the
gene sequence is
affected by the
mutation
• So, only one amino
acid changes in the
hemoglobin protein.
• The hemoglobin still
functions but it folds
differently changing
the shape of the rbc.
Think – pair - share
• Which type(s) of mutation would have the most
affect on an organism?
• Insertion and deletion mutations have the
most effect on an organism because they
affect many amino acids and consequently
the whole protein.
CGA – TGC – ATC
Alanine – Threonine – stop
Mutated DNA: CGA – TCA- TC
Alanine – Serine
Mutated DNA: CGA – TAG – CAT – C
Alanine – Leucine - Valine
Normal DNA:
An example of a frameshift mutation
disorder is Tay Sachs disease.
• Children born with this
disorder cannot make an
enzyme that is critical in
breaking down fat and
toxic substances in the
brain.
• The disease is terminal.
Most will die before age
4.
Think – pair - share
• In which cells would a gene mutation
have the greatest affect on an organism?
Egg being fertilized
• When it is inherited
from the gametes or
develops early in
embryonic
development (in stem
cells or first few
days).
Four cell Zygote
Embryo
Mutagens
• What causes mutations?
– natural errors during replication
– an environmental mutagen/carcinogen
• What is a mutagen (carcinogen)?
something that causes the DNA code to
change (mutate) – x-ray, chemicals, UV
light, radiation, etc
• What happens to a person who has a
mutation?
Chromosomal Mutations
think – pair - share
• How do you think we could mutate
(change/damage) a chromosome?
• List at least 3 ways
Chromosomal Mutations
• Changes in the
number or structure
of chromosomes
• Deletions
• Duplication
• Inversion
• Translocation
• Nondisjunction
Deletions
• removal of a gene and/or entire chromosome
Duplication
• repeat of a gene
or chromosome
Inversion
• gene sequences
are switched on
the chromosome
Translocation
• part of one chromosome breaks off and
reattaches to a non-homologous
chromosome
Think - pair - share
• Compare and contrast translocation with
crossing – over
–How are they similar?
–How are they different?
Non-disjunction
• A chromosome fails to separate from its
homologue during meiosis
Down’s Syndrome
• Result of nondisjunction of the chromosomes
at pair #21
Homework
• Chromosome Mutation activity
Standards:
• CLE 3210.4.6 Describe the connection
between mutations and human genetic
disorders.
Objectives: (DID WE…)
• Investigate the affect of mutations on protein
production
• Differentiate between point mutations and
chromosomal mutations.
Exit Ticket
• How do mutations affect the production of a
protein?