Question | Answer |
Constitutive (house keeping) | –60-80%
–Expressed constantly
•Glycolysis enzymes |
Controlled genes are : | Expressed only if needed
Inducible or Repressible |
Inducible | –lac (lactose) operon |
Repressible | trp(tryptophan) operon |
Inducible operon (lac operon) has an ______________ protein | Active repressor protein |
Inducible | –Induces synthesis of enzymes involved in lactose utilization
–Responds to presence of lactose |
Repressible has an _______ protein. | Inactiverepressor protein |
Repressible operon (trp operon) | –Represses tryptophan synthesis
–Responds to presence of tryptophan |
Regulatory gene (constitutive) | –Codes for a repressor protein |
Promoter | –Site where RNA polymerase starts transcription |
Operator | –Binding site of active repressor protein
–Allows or interferes with the binding of RNA polymerase to promoter |
Structural genes | –Genes under control of the operon |
Lactose operon is influenced | by glucose concentration |
Low cyclic adenosine monophosphate (cAMP)production | High glucose concentration |
Low glucose concentration | High cAMP production |
cAMP binds to a | catabolic activator protein (caP) |
CAP facilitates binding of | RNA polymerase to promoter |
Mutations are: | Permanent” change in the base sequence of DNA |
Variable effect of Mutations: | •Disadvantageous (most often)
•Advantageous
•Neutral |
Base substitution or point mutation (most common) : | Silent mutation
Missense mutation
Nonsense mutation |
Different codon, still same amino acid | Silent mutation |
Amino acid substitution, different amino acid | Missense mutation |
Nonsense mutation | Nonsense (stop) codon, early termination of translation |
Frameshift mutation | Insertion or deletion of nucleotide pairs
–Long stretch of wrong amino acids |
Chemical mutagens Nitrous acid (HNO2) | Adenine (A) change •Pairs with citosine (C)
•Some AT pairs in parent DNA change to CG in granddaughter cells |
Similar to normal nucleosides, but with different base-pairing properties | Nucleoside analogs |
Ionizing radiation | X rays and gamma rays
•Generates highly reactive free radicals
•Damage of DNA
•May break covalent bonds |
Nonionizing radiation | –Ultraviolet (UV) light
•Formation of thymine dimers
–Interferes with transcription and replication |
Eukaryotes (vertical) | –Formation of reproductive cells |
Mediated by bacterial viruses | Bacteriophages (phages) |
Prokaryotes (vertical and horizontal) | –Transformation
–Conjugation
–Transduction |
Transformation | Transfer “naked” DNA in solution (from dead cells) among closely related organisms
•Natural process only in a few types of bacteria
•Major technique in genetic engineering |
Cell processes phage DNA | –Replication
–Transcription
–Translation |
Phage injects its DNA | into host bacterial cell |
Generalized | •Transfer of any bacterial gene
•Lysis of host |
Specialized | •Transfer of an specific gene
•Normal reproduction until the lytic cycle is triggered |
Natural selection | –Survival of the fittest |
Diversity | –Mutation
–Recombination
–Transposition |
–Transposase | •Cutting and resealing DNA
•Recognizes recombination sites |
Movable genetic elements | –Carry information for own transposition
–Move within DNA molecule
–Move to a different DNA molecule
–May carry antibiotic resistance genes |
Extrachromosomal genetic material | Self-replicating
–1 to 5% the size of bacterial chromosome
–Usually not indispensable |
Phage DNA and coat proteins are | are assembled into new phages |
Usually not indispensable | |