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41 Cards in this Set

  • Front
  • Back
Germ-line mutations
mutation in germ cells, passed on to future generations
Somatic mutations
mutation in somatic cells, passed on to daughter cells
Base substitutions
the alteration of a single nucleotide in the DNA
purine to purine or pyrimidine to pyrimidine
purine to pyrimidine or vice versa
Insertions or deletions
addition or removal of one or more nucleotide pairs
Expanding nucleotide repeats
mutations in which the number of copies of a set of nucleotides increases in number. Can be caused by a hairpin loop in replication.
Nucleotide repeats and anticipation
increases in nucleotide repeats can repeat in successive generations, allowing for more expression of a certain gene and resulting in greater expression of a protein and it's phenotype
Forward mutation
alters wild-type to mutant type
Reverse mutation
alters mutant-type to wild-type
Missense mutation
changes the type of amino acide from one to another
Nonsense mutation
changes a sense codon to a nonsense codon (read amino acid codon to termination codon)
Silent mutation
codon to a synonmous codon that still specifies the same amino acid
Neutral mutation
codon specifies a different amino acid, but does not affect overall protein function
Loss-of-function mutation
complete or partial loss of a previous function (negative or positive)
Gain-of-function mutation
produces an entirely new trait to appear at innapropriate tissues or time
Suppressor mutation
hides the affect of another mutation. (Red eyes to white eyes to red eyes, either by suppression or reverse mutation)
Conditional mutation
expressed under certain conditions
Lethal mutation
this kills the host
Intragenic suppressor mutation
mutation in the same gene as the mutation it is suppressing
Intergenic suppressor mutation
mutation in a gene affects a separate mutation in a different gene. Say a first mutant mRNA is suppressed by a different genes mutant tRNA.
Insertions arise because
looping out of newly synthesised strands results in the additional synthesis of a nucleotide
Deletions arise because
looping out of the template strand will result in a nucleotide being missed during replication
the spontaneous loss of a purine. Can happen because of a break in the covalent bond between 1' and doxyribose, resulting in an apurinic site that can't be replicated
the spontaneous loss of an amino group, modifying which base is present (C -> U or 5-Methyl -> T). Can also be induced by certain mutagens
chemical agents that significantly increase the rate of mutation
Base analogs
mutagens with structures similar to the 4 standard DNA base pairs
Alkylating agents
donate alkyl groups
adds hydroxyls. Acts only on cytosine.
Oxidative reactions
turing deoxyriboses to riboses or vice versa
Intercalating agents
produce mutations by inserting themsevels between adjacent bases in DNA
Pyrimidine dimers
created by ionizing or UV radiation, causing a bond to form between two pyramidines (most often T's)
SOS system
a last ditch effert to circumvent pyrimidine dimers, but at the cost of many mistakes in replication
Mistmatch repair
incorrectly paired bases are detected and corrected by specific enzymes. Also corrects some strand slippage. In E. Coli, this is done by matching old methylated strands with the new unmethylated strands, and mismatch strands are removed by exonucleases and then re-replicated.
Direct repair
Changes a base pair back directly, instead of replacing them
Base excision
A modified base is excised and then the entire nucleotide is replaced
Nucleotide excision
removes DNA legions and replaces them
Homologous recombination
repairs double-strand breaks by using a nearbly DNA molecules information and many of the same techniques as used in crossing over.
Nonhomologous end joining
Used in G_1 cells where siter chromatids aren't available. Utilizes proteins that recognize the broken ends of dn and binds them together. More error prone.
Two purines
A and G
Three pyrimidines
C, T, U