2. Regents Biology
Mutations
Changes to DNA are called mutations
change the DNA
changes the mRNA
may change protein
may change trait
DNA TACGCACATTTACGTACG
mRNA AUGCGUGUAAAUGCAUGC
aa aa aa aa aa aa aaprotein
trait
3. Regents Biology
Types of mutations
Changes to the letters (A,C,T,G bases) in
the DNA
point mutation
change to ONE letter (base) in the DNA
may cause change to protein, may not
frameshift mutation
addition of a new letter (base) in the DNA
sequence
deletion of a letter (base) in the DNA
both of these shift the DNA so it changes how
the codons are read
big changes to protein!
4. Regents Biology
Point Mutations
One base change
can change the meaning of the whole protein
THEFATCATANDTHEREDRATRAN
THEFATCARANDTHEREDRATRAN
THEFATCATENDTHEREDRATRAN
OR
Does this change
the sentence?
A LITTLE!
5. Regents Biology
Point Mutations
Missense mutation = changes amino acid
AUGCGUGUAUACGCAUGCGAGUGA
MetArgValTyrAlaCysGluStop
AUGCGUGUAUACGUAUGCGAGUGA
MetArgValTyrValCysGluStop
Does
this change
the protein?
DEPENDS…
6. Regents Biology
Sickle cell 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
7. Regents Biology
Point Mutations
Silent mutation = no change to protein
AUGCGUGUAUACGCAUGCGAGUGA
MetArgValTyrAlaCysGluStop
AUGCGUGUAUACGCUUGCGAGUGA
MetArgValTyrAlaCysGluStop
Does this change
the protein?
Why not?
The code has
repeats in it!
8. Regents Biology
Point Mutations
Nonsense mutation = change to STOP
AUGCGUGUAUACGCAUGCGAGUGA
MetArgValTyrAlaCysGluStop
AUGCGUGUAUAAGCAUGCGAGUGA
MetArgValStop
Really destroyed
that protein!
9. Regents Biology
Frameshift Mutations
Add or delete one or more bases
changes the meaning of the whole protein
THEFATCATANDTHEREDRATRAN
THEFATCANTANDTHEREDRATRAN
THEFATCAANDTHEREDRATRAN
OR
Add one!Delete one!
Does this change
the sentence?
A LOT!
10. Regents Biology
Frameshift Mutations
Addition = add one or more bases
AUGCGUGUAUACGCAUGCGAGUGA
MetArgValTyrAlaCysGluStop
AUGCGUGUAUACGUCAUGCGAGUGA
MetArgValTyrValMetArgValA
Does this change
the protein?
A LOT!
11. Regents Biology
Frameshift Mutations
Deletion = lose one or more bases
AUGCGUGUAUACGCAUGCGAGUGA
MetArgValTyrAlaCysGluStop
AUGCGUGUAUACGAUGCGAGUGA
MetArgValTyrAspAlaSerGA
Does this change
the protein?
A LOT!
12. Regents Biology
Cystic fibrosis
Broken salt channel in cells
strikes 1 in 2500 white births
gene codes for a protein channel
that allows salt to flow across cell membrane
broken protein doesn’t work as channel
doesn’t allow salt out of cell, so water doesn’t flow out
either
thicker & stickier mucus coating around cells
mucus build-ups in lungs & causes bacterial infections
destroys lung function
without treatment children die before 5;
with treatment can live past their late 20s
13. Regents Biology
Salt channel
transports salt through protein
channel out of cell
Osmosis problems!airway
salt
H2O
H2O
salt
normal lungs
cystic fibrosis
cells lining
lungs
salt channel
normal mucus
thick mucus
mucus & bacteria build up
= lung infections & damage
Cystic fibrosis is an inherited disease that is relatively common in the U.S. Cystic fibrosis affects multiple parts of the body including the pancreas, the sweat glands, and the lungs. When someone has cystic fibrosis, they often have lots of lung problems. The cause of their lung problems is directly related to basic problems with diffusion and osmosis in the large airways of the lungs.
People without cystic fibrosis have a small layer of salt water in the large airways of their lungs. This layer of salt water is under the mucus layer which lines the airways. The mucus layer in the airways helps to clear dust and other inhaled particles from the lungs.
In people without cystic fibrosis, working cystic fibrosis proteins allow salt (chloride) to enter the air space and water follows by osmosis. The mucus layer is dilute and not very sticky.
In people with cystic fibrosis, non-working cystic fibrosis proteins mean no salt (chloride) enters the air space and water doesn't either. The mucus layer is concentrated and very sticky.
People with cystic fibrosis have lung problems because:
Proteins for diffusion of salt into the airways don't work. (less diffusion)
Less salt in the airways means less water in the airways. (less osmosis)
Less water in the airways means mucus layer is very sticky (viscous).
Sticky mucus cannot be easily moved to clear particles from the lungs.
Sticky mucus traps bacteria and causes more lung infections.
Therefore, because of less diffusion of salt and less osmosis of water, people with cystic fibrosis have too much sticky mucus in the airways of their lungs and get lots of lung infections. Thus, they are sick a lot.
