Transcript Biology is the only subject in which multiplication is the same thing

Mutations
Changes to DNA
Regents Biology
2009-2010
Mutations
 Changes to DNA are called mutations
change the DNA
 changes the mRNA
 may change protein
 may change trait

DNA
TACGCACATTTACGTACG
mRNA
AUGCGUGUAAAUGCAUGC
protein
aa aa aa aa aa aa aa
trait
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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
Regents Biology big changes to protein!
Point Mutations
 One base change

can change the meaning of the whole protein
THEFATCATANDTHEREDRATRAN
THEFATCARANDTHEREDRATRAN
OR
THEFATCATENDTHEREDRATRAN
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Point Mutations
 Missense mutation = changes amino acid
AUGCGUGUAUACGCAUGCGAGUGA
Met
Arg
Val
Tyr
Ala
AUGCGUGUAUACGUAUGCGAGUGA
Met Arg
Val
Cys
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Biology Glu Stop
Tyr
Val
Cys
Gl
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
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Point Mutations
 Silent mutation = no change to protein
AUGCGUGUAUACGCAUGCGAGUGA
Met
Arg
Glu Stop
Val
Tyr
Ala
Cys
AUGCGUGUAUACGCUUGCGAGUGA
Met
Arg
Glu
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Biology Stop
Val
Tyr
Ala
Cys
Point Mutations
 Nonsense mutation = change to STOP
AUGCGUGUAUACGCAUGCGAGUGA
Met
Cys
Arg Val
Glu Stop
Tyr
Ala
AUGCGUGUAUAAGCAUGCGAGUGA
Met
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Arg
Val
Stop
Frameshift Mutations
 Add or delete one or more bases

changes the meaning of the whole protein
THEFATCATANDTHEREDRATRAN
THEFATCANTANDTHEREDRATRAN
OR
THEFATCAANDTHEREDRATRAN
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Frameshift Mutations
 Addition = add one or more bases
AUGCGUGUAUACGCAUGCGAGUGA
Met
Cys
Arg Val
Glu Stop
Tyr
Ala
AUGCGUGUAUACGUCAUGCGAGUGA
Met
Arg Val
Arg
A
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Biology Val
Tyr
Val
Met
Frameshift Mutations
 Deletion = lose one or more bases
AUGCGUGUAUACGCAUGCGAGUGA
Met
Arg
Glu Stop
Val
Tyr
Ala
Cys
AUGCGUGUAUACGAUGCGAGUGA
Met
Arg
Ser
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Biology GA
Val
Tyr
Asp
Ala
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;
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with treatment can live past their late 20s

Salt channel
Effect on Lungs
normal lungs
airway
salt channel
salt
normal mucus
H 2O
cells lining
lungs
cystic fibrosis
salt
H 2O
transports salt through protein
channel out of cell
Osmosis problems!

thick mucus
mucus & bacteria build up
= lung infections & damage
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Deletion leads to Cystic fibrosis
deletion
Loss of one
amino acid!
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