Download Frameshift Mutations

GET READY FOR A GOOD DAY!!! (GET
HYPE!)
Unit 6
MUTATIONS
Title: DNA Mutations
(5 minutes)
Let’s Play Telephone.
What happened?
Agenda
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•
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•
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•
Bellringer (5min)
Introduction (5min)
Input (15min)
Group Work (25min)
Review (10min)
Independent Practice (20min)
Exit Quiz (10min)
Think – Pair - Share
Read the following two sentences:
THE DOG BIT THE CAT
THE DOG BIT THE CAR
1. What happened when a single letter in the
sentence was changed?
2. If you changed any other letter, will the sentence
continue to make sense?
3. What would happen to the sentence if we were to
delete the letter G?
4. You are a scientist, how would you describe this
change you observed?
5. What would you name it?
• What you just observed is
called a mutation!
• Mutations are changes
in the genetic material.
What caused the “mutation”
in your final product during the Telephone
game?
A mutagen is something that causes
a mutation.
Ex: radiation, chemicals, high temp.
Mutations in Body vs. Sex Cells
 Mutations:
- In sex-cells: can lead to
changes producing offspring
with new characteristics.
 BAD: May result in embryo not
surviving.
 GOOD: May provide organism
with an advantage.
(EVOLUTION)
- In body cells: affect only the
individual and may result in cancer.
A. Chromosome mutations
 Chromosome mutations are changes in
entire chromosomes
 Sometimes a mistake happens during cell
division which can lead to chromosome
mutations, or even more damaging, can lead to
something called non-disjunction.
A B C D E
F G H
A B C E
Deletion
F G H
Chromosome mutation
 Nondisjunction is the failure of
chromosomes to separate during
the division of chromosomes in the
sex cells.
 Nondisjunction causes the genetic
disorder Down Syndrome; the baby
has an extra chromosome 21.
Chromosomal mutations
B. Gene Mutations
produce changes in a single gene.
 There are 2 main types: Point and Frameshift.
Read the following two sentences:
THE DOG BIT THE CAT
THE DOG BIT THE CAR
Where is the mutation?
What happened to the last “codon” ?
What word would you use to define what
happened to the last base (letter) of that
codon?
In science we call this a Point mutation
(Substitution)
1. Point mutation (substitution)
-A change in one base pair in a DNA
sequence.
-A point mutation can cause an amino acid to change, which
will change the structure of the protein being made.
Example: AUG=Met
AAG=Lys
-Only one letter was changed (the A to a U) and the entire
amino acid changed (from methionine to lysine).
Nonsense mutations: result in a
stop codon
STOP codons:
in RNA:
UAG
UAA
UGA
Point mutations in our lives!
Missense Ex: Sickle Anemia

Hemoglobin protein in red blood cells
strikes 1 out of 400 African Americans
 limits activity, painful & may die young

Normal
round cells
Misshapen
sickle cells
Only 1 out of
146 amino acids
Point mutations in our lives!
-People with sickle cell
anemia often
experience a lot of
pain and swelling
and have trouble
exercising.
-BUT, that’s not an
excuse…
(Ryan Clark, a player
for the Steelers)
Read the following two sentences:
THE DOG BIT THE CAT
THE DOB ITT HEC AT
What happened to the code above?
What word would you use to define what
happened to the codons?
2. Frameshift mutation
-Frameshift mutation-adding or deleting
nucleotides to a DNA sequence.
-A frameshift mutation is much worse than a point
mutation because it causes the entire DNA
sequence to be shifted over!
Example: DNA: ATTAAACCG
Delete this T
ATAAACCG
Frameshift Mutations
• Crohn’s Disease is caused by a frameshift
mutation.
• It causes inflammation to the digestive tract.
Gene Mutations:
Types of Mutations in Translation
Point (letter gets
substituted)
Missense
(changes
amino
acid)
Nonsense
(Changes amino
acid/stop codon)
Silent (does
not change
amino acid)
Frameshift (letter
gets
deleted/inserted)
Addition
(letter is
added)
Deletion
(letter is
deleted)
Questions:
Is this a point mutation or a frameshift mutation?
-It’s a point mutation because only one nucleotide
changed!
Break the mRNA into codons!
GUAUUUGCGAUG
GUA-UUU-GCG-AUG
How many codons do I have?
4 codons
Questions:
THE DOG BIT THE CAT
THE DOG BIT THE CAR
Point or frameshift?
Point!
Why?
Questions
THE DOG BIT THE CAT
THE DOB ITT HEC AT
Point or frameshift?
-frameshift
Why?
ATTENTION: Review in
preparation for your Group practice
Use the codon chart to translate
the codons into amino acids
Frameshift Mutations: How is this
deletion?
AUGCGUGUAUACGCAUGCGAGUGA
MetArgValTyrAlaCysGluStop
Mutation!
AUGCGUGUAUACGAUGCGAGUGA
MetArgValTyrAspAlaSerGA
Does this change
the protein?
A LOT!
Frameshift Mutations: How is this
addition?
AUGCGUGUAUACGCAUGCGAGUGA
MetArgValTyrAlaCysGluStop
AUGCGUGUAUACGUCAUGCGAGUGA
MetArgValTyrValMetArgValA
Does this chang
the protein?
A LOT!
Point Mutations
How is this a substitution?
THEFATCATANDTHEREDRATRAN
THEFATCARANDTHEREDRATRAN
OR
THEFATCATENDTHEREDRATRAN
Does this change
the sentence?
A LITTLE!
Point Mutations(Substitution)

Why is this missense?
AUGCGUGUAUACGCAUGCGAGUGA
MetArgValTyrAlaCysGluStop
RADIATION!
AUGCGUGUAUACGUAUGCGAGUGA
MetArgValTyrValCysGluStop
Does
this change
the protein?
DEPENDS…
Point Mutations

Why is this silent?
AUGCGUGUAUACGCAUGCGAGUGA
MetArgValTyrAlaCysGluStop
AUGCGUGUAUACGCUUGCGAGUGA
MetArgValTyrAlaCysGluStop
Does this change
the protein?
Why not?
Point Mutations

Why is this nonsense?
AUGCGUGUAUACGCAUGCGAGUGA
MetArgValTyrAlaCysGluStop
AUGCGUGUAUAAGCAUGCGAGUGA
MetArgValStop
Really destroy
that protein!
Group Practice (25min)
• Work with your group to solve your guided
practice worksheet
Let’s quickly review what we’ve
learned so far…
Why is the genetic code universal?
• All organisms have DNA
made of the same
molecules.
– DNA in every organism
has the bases: A,T,C,G
• Why are there
similarities in the
genetic code of similar
organisms?
- Most organisms share a
common ancestry
DNA Replication
•
•
•
•
•
Unwind
Unzip (Helicase)
Start (Primase)
Attach bases (Polymerase)
Glue (Ligase)
• DNA is semi-conservative:
• At the end of the process, there are two,
identical strands of DNA, each with
part of the original strand and a newly
created strand.
Central Dogma:
• DNA  RNA  Protein
• DNA Replication= making an identical
copy of a DNA strand
• http://www.youtube.com/watch?v=_Q2Ba2cFAew
Replication – 1 minute video
http://www.youtube.com/watch?v=4jtmOZaIvS0&safe=active
– TRANSCRIPTION:
– RNA polymerase reads one side of the DNA template
and strings together a complementary strand of RNA
nucleotides.
– The DNA helix winds again as the gene is transcribed.
DNA
RNA polymerase
moves along the DNA
• RNA differs from DNA in three major ways.
– RNA has a ribose sugar.
– RNA has uracil instead of thymine.
– RNA is a single-stranded structure.
After transcription, the ribosomes have this
foreign message that means nothing to them.
So they must “translate” it
Translation
• Turns mRNA into
an amino acid
chain (protein)
• It occurs in the
cytoplasm using a
ribosome
Mutations are changes in DNA that
may or may not affect phenotype.
Some mutations affect a single gene,
while others affect an entire chromosome.
Why don't all mutations result in visible
change?
• Not all mutations are harmful,
some may be beneficial, and
may not be visible (silent
mutation).
– Silent mutations occur because
the same amino acid is created
despite the error.
 Independent Practice (20min)
Complete:
Silently
Independently
Exit Ticket (10min)
Homework
• Finish Worksheet
• Study for DNA
Replication,
Transcription, and
Translation, and
Mutation Unit Exam