mutations from gene to protein honors biology ms. kim
TRANSCRIPT
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Mutations
From Gene to ProteinHonors Biology
Ms. Kim
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Mutations
• Mutations–Are changes in the genetic material (DNA)
of a cell2 TYPES
• 1. Point mutations can affect protein structure and function–Are changes in just one base pair of a gene
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POINT MUTATIONS
• The change of a single nucleotide in the DNA’s template strand–Can lead to the production of
–an abnormal protein or…–the same protein
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Point Mutations
• Point mutations within a gene are called–Base-pair substitutions
• Can result in a mutation (change) that is• harmful• neutral (not harmful or helpful) • beneficial
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Substitutions• 2 TYPES–missense (wrong amino acid)• ONLY 1 wrong aa is added to polypeptide…all the
other aa’s are the same – nonsense (prematurely STOP)• The change in DNA leads to an early STOP codon
polypeptide is SHORTEN!!
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POINT MUTATION ANALOGY…
• TEMPLATE: THE CAT ATE THE RAT
• POINT MUTATION: THE CAT ATE THE RAT – THE CAT ATE THE BAT What kind of point
mutation is this?• MISSENSE
– THE CAT ATE THE XAT What kind of point mutation is this?• NONSENSE
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What is the “wobble” effect? • The last base (nucleotide) in a codon is said to be in the
WOBBLE position.– codon mutation may encode the same amino acid
• Leads to NEUTRAL or SILENT mutations– Not harmful or helpful
• SILENT MUTATIONS• Mutation does not change “end result”…change in DNA
still makes the SAME amino acid• NO noticeable change occurs• a change from AUU to AUC will still encode leucine
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What is a neutral mutation?
• May or may not affect the resulting protein.– For example, if the codon AAA is mutated to
AGA, arginine would be used in the resulting protein instead of lysine
– These amino acids are chemically similar and may not have a large effect in the protein or its function
– IF this change causes the protein to not function (and be LETHAL to the organism) then it is not a neutral mutation but rather a missense mutation
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2. Frameshift Mutations
• Insertions and deletions–Are additions or losses of nucleotide pairs in a
gene– produce frameshift mutations• 2 TYPES– Insertions–Deletions
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FRAMESHIFT MUTATION ANALOGY…
• TEMPLATE: THE CAT ATE THE RAT
• ADDITION of “B” MUTATION: THE CAT ATE THE RAT – THE CAT BAT ETH ERA T What kind of frameshift
mutation is this?• INSERTION
• SUBTRACTION of “A” MUTATION: THE CAT ATE THE RAT
– THE CAT TET HER AT What kind of frameshift mutation is this?• DELETION• http://highered.mcgraw-hill.com/sites/0072552980/student_
view0/chapter9/animation_quiz_5.html
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Which is more harmful?
• Typically, frameshift mutations are more harmful BUT some point mutations can be LETHAL–Ex: Tay Sachs and Cystic Fibrosis
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Other Types of Mutations
• Inversions–“Flip Flops”•Nucleotides trade places on each
strand• Deletions (2+ nucleotides)–Many nucleotides are deleted at once
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Causes of Mutations
• Inherited mutations– From mom and dad
• Spontaneous mutations–occurs during DNA replication
• Environmental mutations (Mutagens)–physical or chemical agents that can cause
mutations• Ex: Sun, viruses, chemicals
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Belgian Blue Cattle (so beefy….)
The Belgian Blue has a natural mutation in myostatin gene, which codes for protein that inhibits muscle development and fat deposition (creates very lean meat).
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Piedmontese cattle (still so beefy…)
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