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

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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 big changes to protein!

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Point Mutations One base change

can change the meaning of the whole protein

THEFATCATANDTHEREDRATRAN

THEFATCARANDTHEREDRATRAN

THEFATCATENDTHEREDRATRAN

OR

Does this changethe sentence?A LITTLE!

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Point Mutations Missense mutation = changes amino acid

AUGCGUGUAUACGCAUGCGAGUGA

MetArgValTyrAlaCysGluStop

AUGCGUGUAUACGUAUGCGAGUGA

MetArgValTyrValCysGluStop

Doesthis changethe protein?DEPENDS…

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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

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Point Mutations Silent mutation = no change to protein

AUGCGUGUAUACGCAUGCGAGUGA

MetArgValTyrAlaCysGluStop

AUGCGUGUAUACGCUUGCGAGUGA

MetArgValTyrAlaCysGluStop

Does this changethe protein?Why not?

The code hasrepeats in it!

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Point Mutations Nonsense mutation = change to STOP

AUGCGUGUAUACGCAUGCGAGUGA

MetArgValTyrAlaCysGluStop

AUGCGUGUAUAAGCAUGCGAGUGA

MetArgValStop

Really destroyedthat protein!

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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!

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Frameshift Mutations Addition = add one or more bases

AUGCGUGUAUACGCAUGCGAGUGA

MetArgValTyrAlaCysGluStop

AUGCGUGUAUACGUCAUGCGAGUGA

MetArgValTyrValMetArgValA

Does this changethe protein?

A LOT!

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Frameshift Mutations Deletion = lose one or more bases

AUGCGUGUAUACGCAUGCGAGUGA

MetArgValTyrAlaCysGluStop

AUGCGUGUAUACGAUGCGAGUGA

MetArgValTyrAspAlaSerGA

Does this changethe protein?

A LOT!

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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

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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

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Deletion leads to Cystic fibrosis

deletion

Loss of one amino acid!

Regents Biology 2009-2010

Not to ask questionsis a mutation!