Download insertion mutation

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.
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
are passed onto offspring.
Mutations in body cells (somatic cells)
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
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?
At the beginning of the gene sequence
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 amino
acid changes in
the hemoglobin.
• 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?
Gene Mutations Activity
• Complete the worksheet
Chromosomal Mutations
think – pair - share
• How do you think we could mutate 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?