2. What are mutations?
• Mutations are changes in the nucleotide sequence of DNA
othey usually happen during DNA replication
oin somatic (body) cells, mutations may affect the
individual
oin gametes (sex cells), mutations can be passed down
and may affect an individual’s offspring
• Mutations occur all the time!
3. What causes mutations?
• Mutations occur all the time!
• There are two ways in which DNA can become mutated:
oMutations can be inherited from parent to child
oMutations can be acquired via
•random DNA replication errors
•environmental damage
4. Are mutations helpful or harmful?
• Many mutations are repaired by enzymes
• Almost all mutations are neutral (have no
effect)
• Mutations can be bad, leading to cancer,
aging, birth defects, and self-aborted
embryos
• Mutations can be good, leading to an
increased chance of survival for the
individual
5. Types of Mutations
• Chromosomal Mutations
oInvolve changes in the number or structure of
chromosomes, therefore often affecting more than one
gene. These mutations can change the location of genes
on chromosomes and can even change the number of
copies of some genes. WE WILL NOT DISCUSS THESE
MUTATIONS IN CLASS AT THIS TIME.
• Gene Mutations
oInvolve mutations in base pairs of the DNA
6. Types of Mutations
• Point Mutations
oGene mutation that involves the change of one nitrogen
base in DNA
oCaused by substitution of one base pair for another in the
sequence
oCan be further classified as missense, nonsense, and
silent based on how the “mutated” protein behaves
7. Missense Mutation
Missense (substitution) mutation
GGTCACCTCACGCCA
↓
CCAGUGGAGUGCGGU
↓
Pro-Val-Glu-Cys-Gly
Often referred to as substitution. The base pair change
results in a different amino acid; this may or may not affect
the protein that results (ex. sickle cell anemia)
Normal gene
GGTCTCCTCACGCCA
↓
CCAGAGGAGUGCGGU
Codons
↓
Pro-Glu-Glu-Cys-Gly
Amino acids
10. Types of Mutations
• Frameshift Mutations
oResult from the addition or deletion of a nitrogen base.
oThis type of mutation changes the “reading frame”.
oBy shifting the reading frame”, frameshift mutations can
change every amino acid that follows the point of the
mutation.
oThis mutation results in a completely different protein
than intended.
oThis mutation can alter a protein so much that it is unable
to perform its normal functions.
14. Is mutation a mechanism for evolution?
• If no changes to genomes occur over time, there would be
no evolution
oToo much change in the DNA is harmful
oToo little does nothing
oA balance exists between the amount of new variation
and the overall health (adaptiveness) of the new variant
individual
• Differences between closely related organisms show
closely matched DNA sequences that diverged at some
past time and that was adaptive for a given environment
Editor's Notes
How did Cyclops from the X-Men get his superpowers?
He was born with the mutation
How did the Hulk and Spiderman get their superpowers?
The Hulk was exposed to gamma radiation and Spiderman was bitten by a radioactive spider
While the superpowers and abilities may be fictional, it is true that mutations can have significant impacts on people and evidence exists that radiation exposure can lead to an increased rate of mutations. First, let’s discuss the different types of mutations, then where or how they can occur. We will also talk about some environmental factors that can influence the rate of mutations, and finish by looking at some possible effects of mutations.
Epidermodysplasia verruciformis – makes you grow warts that resemble trees.
Changes in the third base of a codon often have no effect.
With sickle cell disease, an inherited group of disorders, red blood cells contort into a sickle shape. The cells die early, leaving a shortage of healthy red blood cells (sickle cell anemia), and can block blood flow causing pain (sickle cell crisis).
Infections, pain, and fatigue are symptoms of sickle cell disease.
Treatments include medications, blood transfusions, and rarely a bone-marrow transplant.
Cystic fibrosis affects the cells that produce mucus, sweat, and digestive juices. It causes these fluids to become thick and sticky. They then plug up tubes, ducts, and passageways.
Symptoms vary and can include cough, repeated lung infections, inability to gain weight, and fatty stools.
Treatments may ease symptoms and reduce complications. Newborn screening helps with early diagnosis.
Huntington’s is an inherited condition in which nerve cells in the brain break down over time.
It typically starts in a person's 30s or 40s.
Usually, Huntington's disease results in progressive movement, thinking (cognitive), and psychiatric symptoms.
No cure exists, but drugs, physical therapy, and talk therapy can help manage some symptoms.
DiGeorge syndrome is a chromosomal disorder that results in poor development of several body systems. Its features vary widely, even among members of the same family.
The syndrome can cause heart defects, poor immune system function, a cleft palate, and low levels of calcium in the blood.
There's no cure, but treatments can usually address critical health concerns.
