What is a mutation? A mutation is any change in a cells DNA A
mutation can occur in an individual gene - results in a single
changed protein - cystic fibrosis a mutation in the protein that
makes a type of ion channels in cell membrane - bacterial
resistance to antibiotics is an example of a beneficial gene
mutation
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What is a mutation continued A mutation can occur in a
chromosome - a chromosome contains many genes - chromosomal
mutations affect many proteins Examples: Down Syndrome Edwards
Syndrome Cri-du-Chat
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What Causes Mutations? Can be caused by mutagens- a physical or
chemical cause of mutation. Examples: UV light, radiation, drugs,
and benzene. Mutagens are often also carcinogens anything that
causes cancer Can be natural, random events. - mutations occur in
1/100,000 DNA replications Mutations do not have to be bad
(evolution)
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Critical Thinking Will all mutations have a dramatic impact on
an individual? How do you know? Which types of mutations do you
think will have the greatest impact on an organism?
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Gene Mutations
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Kinds of Mutations Substitutions usually affect no more than a
single amino acid. Also known as point mutations
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Kinds of Mutations The effects of insertions or deletions are
more dramatic. The addition or deletion of a nucleotide causes a
shift in the grouping of codons. Changes like these are called
frameshift mutations.
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Kinds of Mutations In an insertion, an extra base is inserted
into a base sequence.
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Kinds of Mutations In a deletion, the loss of a single base is
deleted and the reading frame is shifted.
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Knowledge Check What is a point mutation? Example? What is a
frameshift mutation? Example?
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Chromosomal Mutations Chromosomal mutations involve changes in
the number or structure of chromosomes. Chromosomal mutations
include deletions, duplications, inversions, and
translocations.
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Chromosomal Mutations Deletions involve the loss of all or part
of a chromosome.
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Chromosomal Mutations Duplications produce extra copies of
parts of a chromosome.
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Chromosomal Mutations Inversions reverse the direction of parts
of chromosomes.
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Chromosomal Mutations Translocations occurs when part of one
chromosome breaks off and attaches to another.
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Critical Thinking If Down Syndrome is characterized by having 3
copies of the 21 st chromosomes, would it be explained by a gene or
chromosomal mutation? Which specific type of gene or chromosomal
mutation? Why?
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Significance of Mutations Many mutations have little or no
effect on gene expression. Some mutations are the cause of genetic
disorders. Cancer Down Syndrome