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Regents Biology 2009-2010
12. 4 MutationsChanges to DNA
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
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!
Regents Biology
Point Mutations One base change
can change the meaning of the whole protein
THEFATCATANDTHEREDRATRAN
THEFATCARANDTHEREDRATRAN
THEFATCATENDTHEREDRATRAN
OR
Does this changethe sentence?A LITTLE!
Regents Biology
Point Mutations Missense mutation = changes amino acid
AUGCGUGUAUACGCAUGCGAGUGA
MetArgValTyrAlaCysGluStop
AUGCGUGUAUACGUAUGCGAGUGA
MetArgValTyrValCysGluStop
Doesthis changethe protein?DEPENDS…
Regents Biology
Sickle cell anemia Hemoglobin protein in red blood cells
strikes 1 out of 400 African Americans limits activity, painful & may die young
Normalround cells
Misshapensickle cells
Only 1 out of146 amino acids
Regents Biology
Point Mutations Silent mutation = no change to protein
AUGCGUGUAUACGCAUGCGAGUGA
MetArgValTyrAlaCysGluStop
AUGCGUGUAUACGCUUGCGAGUGA
MetArgValTyrAlaCysGluStop
Does this changethe protein?Why not?
The code hasrepeats in it!
Regents Biology
Point Mutations Nonsense mutation = change to STOP
AUGCGUGUAUACGCAUGCGAGUGA
MetArgValTyrAlaCysGluStop
AUGCGUGUAUAAGCAUGCGAGUGA
MetArgValStop
Really destroyedthat protein!
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 changethe sentence?
A LOT!
Regents Biology
Frameshift Mutations Addition = add one or more bases
AUGCGUGUAUACGCAUGCGAGUGA
MetArgValTyrAlaCysGluStop
AUGCGUGUAUACGUCAUGCGAGUGA
MetArgValTyrValMetArgValA
Does this changethe protein?
A LOT!
Regents Biology
Frameshift Mutations Deletion = lose one or more bases
AUGCGUGUAUACGCAUGCGAGUGA
MetArgValTyrAlaCysGluStop
AUGCGUGUAUACGAUGCGAGUGA
MetArgValTyrAspAlaSerGA
Does this changethe protein?
A LOT!
Regents Biology
Cystic fibrosis Broken salt channel in cells
strikes 1 in 2500 white births
gene codes for a protein channelthat 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
Regents Biology
Salt channeltransports salt through protein channel out of cellOsmosis 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
Regents Biology
Deletion leads to Cystic fibrosis
deletion
Loss of one amino acid!
Regents Biology 2009-2010
Not to ask questionsis a mutation!
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