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Mutations
Mutations
• Change / alteration to the DNA of an organism
• They may be good, bad or have no effect
• A plant that can better tolerate the cold (GOOD)
• A change that causes some syndrome or illness (BAD)
• A change that we never see or notice (NONE)
• A driving force behind evolution
• A plant that can better tolerate the cold (GOOD)
Causes of mutations
• Naturally occurring (they just happen) 2/3 of
all cancers
• Mutagen – something in the environment that
causes a change
• Examples: radiation (x-rays), pollution and
toxic chemicals (Love Canal), smoking, diet,
etc….
Types of mutations
• Genetic – causes a change in the gene
• May only effect one gene
• Change in the base (A,T, C, G)
• Chromosomal – causes a change in a
chromosome or segments of a chromosome
Genetic mutations
• 1.Deletions: remove a base from the sequence
• ATCCGACAG (codons are in groups of 3)
• ATCGACAG
• 2.Insertions: a base is added to the sequence
• ATCCGACAG
• ATTCCGACAG
• These are both called frameshift mutations they
cause a change in how the sequence is read
Types of genetic mutations
• 3. Substitutions: a base is changed (one is
substituted for another)
• AGGCAA
• AGCCAA
• A substitution may not cause any change in
the amino acid
Examples of genetic mutations
• Color blindness – x chromosome (sex linked)
• Hemophilia – x chromosome (sex linked)
(free bleeding)
• Sickle cell – chromosome 11 (causes a change
in the shape of red blood cells)
Chromosomal mutations
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Deletions – chromosome is deleted
Duplication – chromosome is duplicated
Inversion – chromosome is inverted
Translocation – piece of a chromosome is
moved to another chromosome (not
homologous)
• Non-disjunction – chromosomes don’t
separate properly
Examples of chromosomal mutations
• Downs syndrome – trisomy 21 (3 copies of
the 21 chromosome total of 47 chromosomes)
• Turner’s syndrome – x or piece of the x
chromosome is missing (45 chromosomes)
• Klinefelter’s syndrome – xxy (47
chromosomes an extra x chromosome)