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GENETIC MUTATIONS
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What is a Genetic Mutation?
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A mutation is a change in the nucleotide sequence
of DNA
Bases can be accidentally deleted, added, inverted
(flipped), or replaced with different bases
Mutations can occur in the DNA in any of our
cells, but only mutations in our sex cells
(gametes) will be passed on to our offspring
Amoeba Sisters- Mutations
Substitution Mutation
One single DNA
base is changed
Three Types:
Silent,
Nonsense, and
Missense
Silent: One DNA
base is changed
but it does not
change the
amino acid
produced
Nonsense Mutations
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Nonsense Mutation
 DNA
base that is substituted, accidentally
codes for a STOP codon
Missense Mutation
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Missense Mutation
 DNA
base that is substituted codes for a
different amino acid
Insertion Mutation
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One or more bases are inserted into the original
DNA base sequence
This is sometimes called a frameshift mutation
because it shifts the codon reading frame
Deletion Mutation
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One or more bases are deleted
This is also caused a frameshift
mutation
What Causes Mutations?
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Can occur randomly
during the process
of DNA replication
Radiation
(ultraviolet rays, xrays)
Chemicals
(asbestos, tobacco)
Genetic Disorders
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Mutations in DNA can result in many
different diseases and disorders
Diseases occur because a gene now codes
for an abnormal protein or enzyme
It could cause a wrong amino acid to be
produced, and as a result the protein
may not fold correctly
If this protein or enzyme is very important
for the functioning of our body, serious
complications can result
Sickle-Cell Anemia
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Recessive Inherited
disorder
Red blood cells have an
abnormal sickle shape
This shape makes it
difficult for them to carry
oxygen and causes them
to clump together
Caused by a change in a
single base of the gene
that codes for
hemoglobin
Sickle-Cell Anemia
Sickle-Cell Inheritance
Tay-Sachs Disease
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Recessive Inherited Disorder
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Babies lack the enzyme that breaks down lipids in the brain
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Without the enzyme, lipids build up and kill brain cells
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Disease is fatal and death occurs when a child is several
years old
Cystic Fibrosis
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Most common fatal
genetic disorder
Caused by a
recessive allele on
chromosome 7
Causes glands to
produce a thick
mucus that clogs
and damages lungs
Down Syndrome
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Also called “trisomy 21”
because individuals have
an extra chromosome 21
Occurs when
chromosomes do not
divide correctly during
meiosis
Characterized by
developmental delay and
physical abnormalities
Hemophilia
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Blood disorder in which
individuals are unable to
make a certain blood protein
that aids in the clotting
process
Disorder is caused for a
recessive gene that is carried
on the x chromosome
Since males only have one x
chromosome, hemophilia
typically occurs in males
Hemophilia and the
Royal Family
Hemophilia in the Royal Family
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Females are only
carriers
Males are the only
affected individuals
because they only
have one x
chromosome
50% of the male
offspring created by
a female carrier will
have the disease
Hemophilia in the Royal Family