Announcements. http://cwx.prenhall.com/bookbind/pubbooks/klug3/ Self-grading problems = good practice for exam. Review of Last Lecture. 1. Post-transcriptional gene regulation: Alternative splicing 2. Classification of mutations 3. Detection of mutations in humans
Self-grading problems = good practice for exam
1. Post-transcriptional gene regulation: Alternative splicing
2. Classification of mutations
3. Detection of mutations in humans
4. Different forms of mutations
I. Origins of mutation
II. Mechanisms of DNA repair
III. Transposable elements
1. Tautomeric Shifts: spontaneous
2. Base Analogues: chemical
3. Alkylating Agents: chemical
4. Intercalating Dyes: chemical
5. Deamination: chemical
6. UV Radiation and Thymine Dimers
7. High-Energy Radiation (X rays, gamma rays, cosmic rays)
Transition is a purine replaced by different purine or pyrimidine
replaced by different pyrimidine.
Incorporate 5-BU in place of Thymine
Changes T-A pair > C-G pair. T > C, and A > G are both Transitions
Sulfonate (EMS) Alkylates Guanine
Note: changes a G-C pair into an A-T pair
(G > A is a transition, C > T is a transition)
Another example: mustard gases first used in WWII.
Intercalate themselves into the DNA double helix, distorting it,
and causing insertion or deletion during DNA replication or
recombination. Other examples: Ethidium Bromide, DAPI.
(a) Causes: C -> U/T transition (and G -> A transition)
Causes: A -> G transition (and T -> C transition).
Deamination can be spontaneous as well.
good for sterilization
of bacteria, bad for skin cancer.
1986 - nuclear reactor in Chernobyl, Soviet Union overheated, exploded, and ejected radioactive material into the environment - largest radiation accident in world.
Gamma rays emitted from radioactive elements are a source of ionizing radiation: 31 killed, 200 + acute radiation sickness, longterm effects ???
No increase so far in # of leukemias, but significant increase in # of childhood thyroid cancers
normal - 0.5-3 cases / million children
now- 100 cases / million children
Ionizing radiation transforms stable atoms into reactive free radicals and ions, which cause mutations in DNA
Category Dose (mSv, millisievert)
Lethal full-body dose 3000
Detectable increase in cancer > 200
Chernobyl cleanup worker 250
Chernobyl nearby resident 50
Germany resident 0.4-0.9
Average yearly medical 0.39
Yearly background 2-3
Yearly smoking 2.8
bond between T’s
DNA Pol I, DNA ligase
DNA Pol I
Mottled redness and
pigmentation sign of
damage due to UV
to cancer. 4 years old.
Carefully protected from
sunlight. 18 years old.
Works as a model.
7 Complementation Groups deficient in Excision Repair identified by Cell-cell Hybridization.
Post-Replication Repair in Prokaryotes involves an Intentional Recombination
Using mutations to study gene function in the lab
Change 1 or more nucleotides in a gene to change a triplet codon and thus the amino acid sequence of the protein
Introduce mutated gene into animal
Determine effect on gene expression and protein function
Corn Kernel Pigmentation Phenotype Caused by Ac-Ds Transposition: Colored Aleurone