DNA mutations Flashcards
Any change in the bp seq of the coding or regulatory region in the DNA is which kind of mutation?
Point Mutation
Germline mutation causes?
Affects the next generation,
Mutations are passed to the next generation,
Changes in the seq of germ-cells
Mutation rate-
occurrence of a specific kind of mutation in a cell per generation.
Mutation frequency-
Occurrence of a specific kind of mutation per individual cell or people.
Types of point mutation?
Base pair substitution,
Insertion and deletion
types of base pair substitution
Transition and Transverse
Effect of Insertion and deletion mutation?
Frameshift mutation, affecting the reading frame
Transition mutation-
one pair of purine-pyrimidine is replaced by other.
Transverse mutation-
pair of purine-pyrimidine is replaced by pair of pyrimidine-purine pair.
Effect of bp substitution on the translation of the strand
Missense mutation
Non-sense mutation
Synonymous or silent mutation
Neutral mutation
Missense mutation-
Alteration in the sequence of DNA causes the production of faulty proteins
Non-sense mutation
alteration causes the addition of a stop codon
Neutral mutation-
Change in bp causes the addition of an amino acid that is similar to the original amino acid in terms of properties.
Silent or synonymous mutation-
Change in bp sequence still adds the original amino acid
types of point mutation based on the effect on phenotype?
Forward mutation
Backward mutation
True reversion
Partial reversion
Forward mutation is-
Change from wildtype to mutant phenotype
Reverse mutation
mutation in mt causes reversion to the wt or near wt phenotype.
True reversion
if reverse mutation restores the original amino acid sequence
Partial reversion
when reversion occurs in another amino acid and restores the function either fully or partially.
Suppressor mutation
Mutation that causes the masking or diminishing the effect of other mutations by causing mutation in the same gene on another site or on other genes.
Types of suppressor mutation?
Intergenic
Intragenic
Intergenic suppressor mutation -
suppressor mutation on other genes
Intragenic suppressor mutation
Suppressor mutation on the same gene but at different site.
Induced mutation
Due to exposure to certain chemical or physical agents.
Spontaneous mutation
Naturally occurring mutation
Conformation of bases in watson-crick pairing
Keto form of bases
A=T
G=C
Conformation of bases in non-watson pairing
Enol form of bases
C=A
T triple bond G
Enol and keto forms are-
Tautomeric form of bases
Define tautomers
Isomers that are readily interconvertible with one other.
what is looping of strand?
Displacement of a base at the strand or addition of an extra base during replaction causes the formation of a loop.
Effect of looping of strand?
Can cause mutation by skipping the base in the loop leading to deletion or insertional mutation.
Spontaneous chemical changes
Depurination
Deamination
Depurination-
Removal of purine moiety forming an apurinic site.
which base has weak bond with the sugar moiety?
Purine
Deamination is-
loss of amine group from the base
Deamine cytosine is
Uracil
Most common form of modified cytosine is-
5-methylcytosine
Deamination of 5-methylcytosine will give-
Thymidine
Deamination and depurination can be treated by
Base-pair excision repair
Ionizing radiation
that can excite and knock off an e from it shell.
Only non-ionizing radiation that can cause mutation
UV rays
thymidine dimer is due to
UV radiations
Effect of ionization on bonding between sugar and phosphate?
It breaks the covalent bonds
Chemical mutagens
Base analogs agent
Base modifying agent
intercalating agent
Base analogs of Thymine
5-Bromouracil and binds to Adenine
Tautomeric form of 5-Bromouracil
Behaves like Guanine and binds to cytosine
Analog of thymine which is used to treat AIDS patients
Azidothymidine
Base modifying agent
Deaminating agent
Hydroxylating agent
Alkylating agent
Deamination agent example
Nitrous acid (HNO2)
Hydroxylating agent example
Hydroxylamine (NH2OH)
Alkylating agent example
Methyl-methane sulfonate (MMS)
Effect of HNO2(Nitrous oxide) on guanine?
Become Xanthine which is similar to Guanine and hence no mutation
Effect of HNO2 (Nitrous oxide) on cytosine
Uracil (CG to AT mutation) formation
Effect of HNO2 on Adenine
Formation of Hypoxanthine (AT to GC mutation)
Which base is specifically affected by hydroxylamine (a hydroxylating agent)
Cytosine, adds OH group to it and forms Hydroxylamine-cytosine
Hyroxylating agent effect on cytosine-
CG to AT mutation
Effect of hydroxylating agent can be reversed by treating it with
5-BU or Nitrous acids like HNO2
most common target of Alkylating agent?
6-carbon of guanine forming O-6 methylguanine
effect of alkylating agent like MMS on guanine is
CG to AT mutation
Intercalating agent
Add or deletes base pairs and causes frameshift mutation
Benzpyrene metabolize to form
Benzpyrene diol epoxide which is carcinogenic.
