Download DNA Mutations

MUTATION NOTES
Objectives
Contrast gene mutations with chromosomal mutations
Mutations
• What is a mutation?
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– **Some mutations affect a _____________, while others affect an entire
______________.
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What causes mutations?
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Mutations that affect a single gene happen:
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During replication or cell division
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because of mutagens in the environment
Whereas mutations that affect an entire chromosome happen during meiosis.
Causes of mutations continued…
• Replication errors
– If DNA polymerase does not fix the small number of errors, they build up over
time and eventually __________________________________
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For example, many studies suggest that mutations are a significant cause of
__________
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Mutagens
– Mutagens are _____________________________ that can change DNA.
They speed up the rate of _____________________, in some cases even
breaking DNA strands
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UV rays in sunshine and industrial chemicals are mutagen examples
– Some kids exposed to radiation from the chernobyl disaster were
affected in such a way that they secrete a compound which means
they can stick metal to them, so they are effectively magnetic. I
wouldn't say it was beneficial as such, but it is rather extraordinary!
– Mutations in the gene that controls the development of the rod in
your eye gives some people night vision. Bonus!
2 Major Types of Mutations
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2 Types of Gene Mutations
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Point mutation
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Frameshift mutation
– one or more bases are _____________________
Point Mutations
• Substitutions
– One base is ____________ to another base
– Like incorrectly writing a single letter in a sentence:
THE APE SAW THE DOG BEG
THE APE SAW THE DOE BEG
What will happen?
• A substitution will cause either a single amino acid change or no change at all.
– Remember that many different ___________________________________
__________________
– If _______changes to ______ due to a mutation, the resulting amino acid will
still be aspartic acid
Frameshift Mutations
• Insertion
– One or more bases are _______ into the DNA sequence
THE APE SAW THE DOG BEG
THE APE SAE WTH EDO GBE G
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Deletion
– One or more bases are ____________ from the DNA sequence
THE APE SAW THE DOG BEG
THE APE SAT HED OGB EG
What will happen?
• A frameshift mutation will shift every base after the mutation, thus _____________
____________________________________________________
So What?
• When the sequence of DNA bases changes, the resulting ________ from transcription
_______________________.
• If the mRNA is different, the amino acid _________________________________.
Chromosomal Mutations
Chromosomal mutations —involve changes in the _________________________________
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Deletion
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Duplication
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Inversion
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Translocation
• Part of one chromosome breaks off and _____________________
________________________________________________
Somatic cells vs Gametes
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Mutations happen both in ____________________________________
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Mutations in body cells _____________ affect offspring. Why?
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Mutations in gametes (sex cells) can be ___________________________________.
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These mutations are the underlying source of ________________________.
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Often the effects of mutations in gametes is so harmful that the offspring does
not develop properly or dies before they can _____________________
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Natural selection often removes mutant characteristics from a population when they
are _____________________
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More rarely, a mutation results in a more _________________ characteristics, these
mutations are favored by natural selection and therefore _______________
Repairing DNA
• Enzymes ________________ the DNA and __________ incorrect nucleotides with
correct nucleotides
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These repair mechanisms work extremely well,_____________________________
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The greater the exposure to a mutagen such as ___________, the more likely is the
chance that __________________________________