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Mutations
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What do YOU think? What are mutations?
Knowing what you know about DNA, how it replicates, and how it codes for proteins… how might a mutation happen? What might be a result of mutations in DNA?
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What are Mutations? Now and then cells make mistakes in copying their own DNA, whether it’s inserting an incorrect base or even skipping a base as the new strand is put together These mistakes are called mutations Mutations are changes in the genetic material
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Types of Mutations Point Mutations – mutations involving changes in one or a few nucleotides They’re called point mutations because they occur at a single point in the DNA sequence Point mutations include: substitutions, insertions, and deletions in the DNA sequence If you had to guess, what do you think happens in each of these three types of point mutations? Substitutions? Insertions? Deletions?
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Types of Mutations Substitutions
A substitution occurs when one base in a DNA sequence is replaced for another Substitutions usually affect no more than one amino acid Why do you think that is?
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Types of Mutations Insertions
An insertion occurs when a base is added to the DNA sequence The effects of an insertion can be much more dramatic than a substitution. Why do you think that is?
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Types of Mutations Deletions
A deletion occurs when a base is removed from a DNA sequence How is a deletion similar to an insertion?
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Types of Mutations Insertions and deletions can have much more dramatic effects because they are considered frameshift mutations Frameshift mutations shift the “reading frame” of the genetic message Remember: the genetic code is read in codons (sets of three letters), so if a base is added/deleted, all the codons after the mutation are affected because it will shift the groups of three
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Types of Mutations By shifting the reading frame, frameshift mutations may change every amino acid that follows the point of the mutation Frameshift mutations can alter a protein so much that it is unable to perform its normal functions
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