DNA mutation & Repair Flashcards
Difference between somatic mutations and gems-line mutations.
- somatic mutations: arise in the DNA of somatic cells(diploid cells), never passed onto the next generation.
- germs-line mutations: mutations arise in the cells that produce sperms or eggs. Can be transmitted to the offspring.
Mutation can be classified by?
- by size (chromosomal & gene)
- What causes the mutation ( spontaneous & induced)
- type of cell that contains the mutated DNA.(somatic&geerm-line)
- others classes of mutations.( Lethal,conditional & suppressor )
Spontaneously mutations vs induced mutations?
- Spontaneously mutations due to natural biochemical events
- Induced mutation due( helped) to some artificial factor.( external conditions, we can somehow prevented)
Main varieties of small gene mutations.
- base pair substitution
- insertions/ deletions
- expansion of trinucleotides repeats ( TNRE)
Difference between conditional mutations and suppressor mutations and lethal mutations.
- conditional mutations: this mutations produce the effect under certain conditions ( example lactose intolerant) .condition does not cause the mutations but allows it to be expressed.
- suppressor mutations: this mutations reverse the effect of a previous mutation.( intragenic vs. interegenic )
- lethal mutations: this mutations are incompatible with life.
Outcome of insertions/ deletions.
An extra nucleotide gets added or removed causing a frameshift. Very bad b/c all a.a after ins/del will be wrong.
Outcome of base pair substitution?
- silent mutations ( usually due to the wobble effect).no effect
- missense mutations( effects varies, could be neutral or not)
(causes the insertion of a wrong a.a, if a similar a.a is inserted, the effect is neutral,but if it’s not, the effect could be bad) - nonsense mutations( change turns into a stop codon, always bad, shorten the peptide)
Difference between chromosomal & gene mutations.
- chromosomal Mutations: large segments of the chromosome are deleted, inverted,moved or multiplied.
- gene mutations:smaller changes in the DNA Sequence
Outcome of expansion of trinucleotides repeats ( TNRE) mutatio s?
Expansion. Could be next to a gene or within the gene.
Abnormal DNA structure causes DNA POL to slip and copy section twice.
- usually lead to a disease.
Usually get worse each generation “ anticipation “
1-What happens if TNRE happens with in the gene?
2-What happens if TNRE happens next to the gene?
1-Within the gene increase the number of a.a ( RNA pol slippage)
2- next to the gene can trigger methylation.
What is a tautomeric shift?
If the nitrogenous base spontaneously turns into its other un common form (the other tautomer) happens 1 % of the time. Very rare
It is reversible but if it doesn’t go back before replication takes place, damage will occur because DNA pol insert the wrong nucleotide. Very rare to happen but possible.
What causes spontaneous damaged?
1-errors of DNA polymerase 2-tautomeric shift 3-Depurination & deanimation 4- oxidative damage 5- transposons
What causes induced damaged?
1-base analogs
2-alkylating agent
3-intercalating agents
4-UV and low energy radiation.
5-high energy radiation ( ionization radiation)
6- viruses ( could be included in both spontaneous or induced)
What are we testing with the Ames test.?
Use to test if a new chemical has the ability to mutate DNA.
Properties of mutations?
Permanent Changed the DNA sequence Create new alleles Random Can not be fix
Intragenic vs. interegenic?
Intragenic: In suppressor mutation the second mutation takes place in the same gene
Intergenic: In suppressor mutation the second mutation takes place in a totally different gene
What does it meant by anticipation when talking TRNE disorders ?
TRNE get worse each generation, expansion grow and worse symptoms.
What causes the most induced damaged to DNA ?
High energy radiation ( ionization radiation )
- produce free radicals
- it directly break phosphodiester bonds
- creates thymine dimmers
Steps in Ames test?
Nose
