Transcript 4 5 6 7 8 - Franklin High School

Mutations – random Replication errors
• Don’t necessarily lead to harm, but some do
• Permanent change in sequence
– If in gamates (sex cells), passed to offspring
• Occur 1/100,000 base pairs
• With proofreading, 1/billion base pairs
• Caused by environmental factors
– Most fixed, but some not
– Smoking, UV radiation
1. Substitution
• Change in a single base in a DNA sequence
• A point mutation
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Point mutation example
• Sickle cell anemia
– changes hemoglobin protein
– Sickle shape
– Doesn’t carry oxygen well
– Clogs capillaries
– On chromosome 11
– Inherited disorder
Point Mutation
Ex. Point mutation - substitution
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Fatal Familial Insomnia Point Mutation
Dominant inherited disease
Can’t sleep so die
10 minute Jon Stossel clip on FFI
2. Frameshift mutations
• Change in nucleotide sequence that causes
each nucleotide to slide down one position
• Significantly changes amino acid sequence.
3. Insertion
• Adding a nucleotide
– Shifts entire frame
• Can be one nucleotide or larger segments
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Gene vs. Chromosomal Mutation
Chromosomal Mutation
Gene
• Changes DNA sequence of
short segment of DNA that
encodes for specific protein
• Changes the number or
structure of entire
chromosomes
4. Deletion
• Single nucleotide or fragment breaks off
• Lost when cell divides
• New cell lacks this set of genes
- 70% of all cystic fibrosis caused by deletion
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Cystic fibrosis - info
• A defective gene and its protein product
– body produces unusually thick, sticky mucus
– clogs the lungs
– leads to life-threatening lung infections
• Also obstructs the pancreas
– stops natural enzymes from helping the body break
down and absorb food.
• YouTube - What is Cystic Fibrosis?
Life with CF
• No cure for CF
– treatments include:
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dietary enzymes
supplements
various methods
medications, such as antibiotics and inhaled steroids, to
clear the airway and improve lung function
• Average life span: 37 years
Video
Point and frameshift mutations
• Point (substitution) and Frameshift insertion
and deletions) mutations
• Extra copy of gene sequence
on same chromosmome
6. inversion
• Fragment reattaches in
reverse order
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5. duplication
hemophilia
• Huntington’s
– Degenerative brain disorder
– Symptoms appear 30-40 years
– Lose ability to walk, think, talk,
reason
7. translocation
• Fragment of chromosome join different
chromosome
• YouTube - Translocation
Video of Mutations
• video on types of mutations
Silent Mutations
• Changes in nucleotide sequence that does not
effect the protein’s function
– Does not change the amino acid sequence
– May occur in “non-coding” region of DNA, introns
Beneficial mutations
• mutations may have a positive effects.
• a specific 32 base pair deletion in human may give some
HIV resistance and delays AIDS onset
• more common in those of European descent.
• Maybe because…
• European population conferred resistance to the bubonic
plague in mid-14th century Europe. People who had this
mutation were able to survive infection; thus, its frequency
in the population increased. It could also explain why this
mutation is not found in Africa where the bubonic plague
never reached.
• New theory states smallpox
More positives of mutations
• Mutations provide the
necessary genetic
variation for species to
be able to change over
time
• EVOLUTION
Harmful mutations
• Changes in DNA caused by mutation can cause
errors in amino acid sequence, creating
partially or completely non-functional
proteins.
• Can be detrimental to organism.