Download Gene Mutations

Bell Ringer 3.24
1. Where does translation occur in the cell?
2. Why do we need RNA to make proteins?
3. How can different codons code for the same
amino acid?
Gene Mutations
DNA:
ATGGTAGCTAACCTT
DNA Comp:
mRNA:
tRNA:
AA:
DNA:
CAGGAATTGCTCGAT
DNA Comp:
mRNA:
tRNA:
AA:
DNA:
GTACTCAAGGTCTAG
DNA Comp:
mRNA:
tRNA:
AA:
DNA:
TTTCAATCGACCAAC
DNA Comp:
mRNA:
tRNA:
AA:
• Mutation =
a change in the DNA sequence
▫ Can change the protein as well
• A mistake that’s made during replication or
transcription
• Can be:
▫ Harmful: diseases or deformities
▫ Helpful: organism is better able to survive
▫ Neutral: organism is unaffected
MOST mutations are NEUTRAL!
1. What does CGC
code for?
2. What does CGG
code for?
3. What does AGG
code for?
4. What does AGA
code for?
5. What does CGA
code for?
Why are so many
mutations neutral?
• If a mutation occurs in a gamete cell
(sex cell), that mutation is passed onto
offspring.
• If a mutation occurs in a body
(somatic) cell, that mutation affects
only the organism and is not passed onto
offspring.
Point Mutations
Bases are
mismatched or
one base is
changed.
(aka substitution)
The Dog Bit the Cat
The Dog Bit the Car
Both of these are sentences. One works perfectly,
the other does not. The point mutation leaves a
sentence with words, but it does not make sense.
The change of one amino acid (word) changes how
the protein (sentence) works.
Point mutations can be harmful when a mistake
results in the wrong amino acid.
One single change can
affect the entire protein.
Silent (Point) Mutations
Not harmful when a mistake is carried into mRNA
but still results in the same amino acid.
Frameshift Mutations
• Bases are inserted (addition) or deleted.
• Usually harmful because it can result in the
coding of many wrong amino acids.
The Dog Bit the Cat
Addition: The Dog eBi tth eCa t
Deletion: The DoB itt heC at
One base pair is deleted or added, and the
entire strand “shifts” over
The deleted “G” or the inserted “E” alters
the entire sequence
Causes of Mutations
Mutagen:
Anything that causes a
change in DNA
Common Mutagens
•
•
•
•
•
X-rays
UV Radiation
Nuclear Radiation
Asbestos
Cigarette Smoke
Cystic Fibrosis (CF)
• Recessive genetic disorder
• An individual with CF has thick mucus in the
lungs and airways, leading to many lung
problems.
• Why is there a build up
of mucus?
Lungs are lined with specialized cells
These special cells clear dust and excess mucus
Mutations in the CFTR gene blocks CFTR protein
function
Healthy Cell
Cystic Fibrosis Cell
Changes in the
DNA sequence
lead to a
protein that
cannot reach
the plasma
membrane
Cystic Fibrosis airways are dehydrated and cannot
clear mucus
Healthy Airway
Normal mucus
CF Airway
Thick, dry mucus
Cystic Fibrosis airways accumulate bacteria and
inflammatory cells
Pseudomonas aeruginosa
Too many inflammatory cells
can cause permanent lung-cell
damange
Cystic Fibrosis Activity
YOU be the Investigator!
Complete Part 1 of the Activity
Upon analysis of samples, you now
have two patients that may have Cystic
Fibrosis.
To give either patient an official
diagnosis, you must sequence their
DNA to see if they have the cftr
mutation.
Complete Part 2 of the Activity
Current Cystic Fibrosis Treatments
1. Bronchodilators
▫
▫
Opens up airways
Oral, injectable, or inhalable drugs
2. Airway clearance techniques
▫
▫
Removes mucus
Coughing and assist devices
3. Antibiotics
▫
▫
Treat infections in airways
Oral, injectable, or inhalable drugs
Gene Therapy
Cystic Fibrosis Cell
Healthy Cell
Addition of
normal cftr gene
to lung cells
Delivered by a
special virus
Goal → replace mutated genes responsible for disease in order to cure the disease
(targets the cause, not the symptoms)
Agenda 3.25…
Bell Ringer
1.
How do feel about your
performance the 1st nine
weeks?
2. What areas do you feel like
you did well in?
3. What areas do you feel like
you need to work on?
4. Does your grade match your
work ethic?
5. Explain #4.
By the bell you need…
1.
2.
3.
4.
5.
6.
Bell Work/TOTD complete.
Mutations Practice
Web Quest (Extra credit)
Cell Membrane!!!!
DNA Paper Model!!
Missing work turned in..
1. Tests/Quizzes
2. Test Corrections
3. Missing
classwork/homework
4. Extra credit