Don’t forget………………
What nitrogen base pairs with Adenine?
What nitrogen base pairs with Guanine?
What is the name given for every set of
three nitrogen bases on the DNA?
What does one codon code for?
When amino acids bond together, what do they form?
Gene Mutations
•Mutations are changes in genetic material or DNA, and they can occur
during DNA replication
•One in every billion base pairs is mutated
•The average person has 6 mutations in each cell
•Mutations are a major source of variation in a population and can help
• organisms evolve (change over time)
•Mutations in gametes are passed on to offspring
•Mutations in body cells only affect the organism in which they
occur and are not passed on to offspring
?
If we have that many mutations and the some can
be harmful, why don’t we look weird?
Mutations are not always seen. Every part of your DNA doesn’t
make a protein or trait. Remember this is called “junk DNA”.
Mutation: damage to genetic material
A mutation to genetic material is usually not
beneficial. Mutagens are things that cause
mutations, they include:
1. High Temperatures
2. Toxic Chemicals (pesticides, etc)
3. Radiation (nuclear and solar)
Many common place items are capable of
causing mutations: microwave, fruit from the
store, radar, cellular phones….
Somatic vs Germ Mutations
•Some people may have
mutations in their skin cells
or hair. Such mutations are
termed Somatic.
•Germ mutations occur only
in the sex cells. These
mutations are more
threatening because they can
be passed to offspring
(forever).
Meiosis is a
prime time for
mutations to
occur.
The germ
mutations that
occur during
meiosis could be
passed on during
fertilization
Mutations affect protein synthesis
Transcription:
Mutated DNA
will produce
faulty mRNA
leading to the
production of
a bad protein.
Types of mutations pages 307-308
Chromosomal:
affecting whole
or a part of a
chromosome
Gene: changes
to the bases in
the DNA of one
gene
Gene Mutations
•Change in the nucleotide
sequence of a gene
•May only involve a single
nucleotide
•May be due to copying errors,
chemicals, viruses, etc.
Types of Gene Mutations
Point Mutation - involve changes in one or more nucleotides in DNA
There are three types:
1. Substitution
2. Deletion
3. Insertion
}
Also called Frameshift Mutations
Types of Point Mutations:
Substitution
Insertion
Deletion
Substitution - one base is changed to another.
• Usually affects a single amino acid in a protein or it may cause
no change in the amino acid
• Has the least harmful affect
An example of substitution mutations is
sickle cell anemia. One amino acid
changes in the hemoglobin, but the
hemoglobin still functions in the RBC,
just not as well.
Frameshift Mutations – changes that cause every codon that
follows the mutation to shift position
• A base is inserted or removed from DNA sequence
• Insertion and deletion mutations have the most effect on an
organism because they affect many amino acids on the protein,
not just one.
Huntington’s Disease is caused by an insertion mutation. People
with this disorder have involuntary movement and loss of motor
control. They eventually have memory loss. The disease is terminal
and similar to Parkinson’s Disease, another motor loss syndrome.
Chromosomal Mutations
• Mutations that change the number or
structure of chromosomes
Original Chromosome
“B”
you’re
out of
here!
Deletion (B is deleted)
Original Chromosome
Duplication (Extra B is added)
Inversion (D & C exchange positions)
Original Chromosome
Translocation
Chromosomal Mutations
• Deletions – all or part of a chromosome is lost or
removed
• Duplications – produce extra copies of parts of the
chromosome
• Inversions – reverse direction of parts of the
chromosomes
• Translocations – occur when part of one chromosome
breaks off and attaches to another chromosome
• Nondisjunctions – occurs when chromosomes do not
separate during meiosis
Chromosome Mutations
Inversion
Are mutation important? How and why?
• Most of the time mutations (neutral) go without
ever being detected
• Harmful mutations disrupt normal biological
activities
Examples: Diabetes. Cancer, and Trisomy 21 (Down
Syndrome)
Some statistics claim that as many as 1 in 700
embryos are Trisomy 21.
• Helpful mutations may produce proteins with
new or altered activities that can be useful to
organisms
Cancer – uncontrolled cell growth in multicellular organisms; cells divide
continually and destroy healthy tissue – pages 252; 962; 1052-1054
Tumors – mass of tissue that grows and divides uncontrollably
benign tumors (noncancerous) do not spread
malignant tumors (cancerous) spread; invade and destroy
surrounding tissue
Liver Cancer
www.cheerzhangover.com/horrors.htm
Cancerous cells under attack
www.zellerx.com/pages/nkcells.html
Causes of Cancer
• Smoking
• Defects in genes that regulate cell growth and
cell division
• Viruses can cause defect in genes or
spontaneous mutations in DNA
• Carcinogens- chemicals which can trigger DNA
mutations (X-rays, forms of radiation, etc.)
Ways to Treat Cancer
• Prevention is best treatment – healthy diet, avoid smoking,
protect against sun and radiation, etc.
• Early detection
• Chemotherapy
• Radiation treatment
• Gene and molecular treatment