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19 terms

Genetics Final Vocab 2

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auxotrophs
mutants unable to synthesize an essential metabolite that is synthesized by wild-type or phototrophic of the same species
temperature-sensitive mutants
grow at one temperature not another; most are heat sensitive, some cold sensitive
suppressor-sensitive mutants
viable when a second genetic factor (suppressor) is present, but they're non-viable in the absence of the suppressor
transition
mutation resulting from tautomeric shifts in the bases of DNA involve the replacement of a purine in one strand of DNA with the other purine and the replacement of a pyrimidine in the complementary strand with the other pyrimidine
transversion
base-pair subs involving the replacement of a purine with a pyrimidine and vice versa
alkylating agent
chemical that donates alkyl groups to other molecules
hydroxylating agent
hydroxyl amine (NH2OH) induces G:C -> A:T transitions
ionizing radiation
x rays, gamma rays, cosmic rays
nonionizing radiation
high energy rays collide with atoms and cause the release of electrons = positively charged free radicals or ions collide with other molecules and release additional electrons
uv radiation
readily absorbed by many organic molecules such as purines and pyrimidines
base excision repair
system removes abnormal or chemically modified bases from DNA
nucleotide excision repair
pathways remove larger defects like thymine dimers
constitutive genes
genes that specify products of this type are continually being expressed constitutively
induction
process of turning on the expression of genes in response to a substance in the environment
inducible genes
genes whose expression is regulated via induction
positive control mechanism
product of the regulator gene is required to turn on the expression of one or more structural genes (specifying the amino acid sequences of enzymes or structural proteins)
negative control mechanism
product of the regulator gene is necessary to shut off the expression of structural genes
catabolite repression
assures that glucose is metabolized when present, in preference to other less efficient energy sources
SOS response
synthesis of a whole set of DNA repair, recombination, and replication proteins in bacteria containing severely damaged DNA