regents biology 2009-2010 mutations changes to dna
TRANSCRIPT
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Regents Biology 2009-2010
MutationsChanges to DNA
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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
aa
protein
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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!
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Regents Biology
Point Mutations ■ One base change
◆ can change the meaning of the whole protein
THEFATCATANDTHEREDRATRAN
THEFATCARANDTHEREDRATRAN
THEFATCATENDTHEREDRATRAN
OR
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Regents Biology
Point Mutations ■ Missense mutation = changes amino acid
AUGCGUGUAUACGCAUGCGAGUGA
MetArgValTyrAlaCysGluStop
AUGCGUGUAUACGUAUGCGAGUGA
MetArgValTyrValCysGluStop
Doesthis
changethe
protein?DEPENDS…
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Regents Biology
Sickle cell anemia■Hemoglobin protein in red blood cells
◆ limits activity, painful & may die young
Normalround cells
Misshapen
sickle cells
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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!
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Regents Biology
Point Mutations ■ Nonsense mutation = change to STOP
AUGCGUGUAUACGCAUGCGAGUGA
MetArgValTyrAlaCysGluStop
AUGCGUGUAUAAGCAUGCGAGUGA
MetArgValStop
Really destroyed
that protein!
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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!
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Regents Biology
Frameshift Mutations ■ Addition = add one or more bases
AUGCGUGUAUACGCAUGCGAGUGA
MetArgValTyrAlaCysGluStop
AUGCGUGUAUACGUCAUGCGAGUGA
MetArgValTyrValMetArgValA
Does this change
the protein?A LOT!
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Regents Biology
Frameshift Mutations ■ Deletion = lose one or more bases
AUGCGUGUAUACGCAUGCGAGUGA
MetArgValTyrAlaCysGluStop
AUGCGUGUAUACGAUGCGAGUGA
MetArgValTyrAspAlaSerGA
Does this change
the protein?A LOT!
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Regents Biology
Cystic fibrosis■ Broken salt channel in cells
◆ 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