How Cellular Information is Altered Flashcards
HOW CELLULAR
INFORMATION IS ALTERED
Mutation and Selection
Natural Mechanisms for Gene Transfer and Rearrangement
Genetically Engineering Cells
Genomics
We can alter cells by using mutation or genetic engineering.
HOW CELLULAR
INFORMATION IS ALTERED
____________ is the purposeful transfer of DNA from one type of organism to another.
Genetic Engineering
_________ is subjecting the cells to stress, causing changes in the genetic make-up.
Mutation
___________ = mistakes in the genetic code (can arise from replication and/or damage)
Mutations
____________ = organism with a genetic mutation
Mutant
_________ = the organism without the genetic organism
Wild type
______________ = genetic construction of an organism
Genotype
_________ = characteristics expressed by an organism.
Phenotype
__________ = usually refers to transcription + translation + post-translation processing.
Expression
If the mutation is in the active site, there may be some _________ consequences.
enzyme activity
If the mutation changes the amino acid to a ________, the resulting _______ will be ________ and probably ___________.
stop codon, protein, truncated, not active
If the amino acid is the same as before the mutation there is _____________
no consequence
If the amino acid is different, but not in the ________ of the active site, there _________
region, may be no consequences.
confers upon the mutant an advantage for growth, survival or detection under a set of environmental conditions that the wild type does not have
Selectable mutation:
Antibiotic resistance
Ability to grow on toluene
Inability to produce lysine
Ability to produce bioluminescence
Ability to produce more of an enzyme
Inability to grow at higher temperatures
SELECTION
____________ mutations per cell conversion
10^-3 - 10^-9
10^-6 = ________________
1 mutation/1,000,000 divisions
_________: chemicals, radiation
Mutagens
Lots of growth (i.e. lots of divisions)
INCREASE MUTATION RATES
WHY DO WE WANT TO
INCREASE MUTATIONS?
We want a cell to develop specific characteristics that are advantageous for us.
_____________: uptake of free DNA by a cell. The cell membrane has to be permeable to DNA.
Transformation
_____________: DNA is carried into the call in a phage.
Transduction
_________: Cell-to-cell transfer of DNA.
Conjugation
Also called mating.
Conjugation
Using ___________, engineers and microbiologists were able to increase penicillin from 0.001 g/L to 50 g/L.
mutation and selection
Using natural mechanisms to purposefully manipulate DNA. The DNA is manipulated outside of the cell, and then sent into the cell.
GENETIC ENGINEERING
__________: enzymes that cut DNA at specific sequences. Different enzymes will cut at different sequences.
Restriction enzymes
______________: A method to detect what sizes of DNA a sample contains.
Gel electrophoresis (Southern Blot)
______________: A process used to make many copies of a piece of DNA.
Polymerase chain reaction (PCR)
_____________: self replicating, circular piece of DNA that can survive in a cell.
Plasmid
________________recognition sequence cuts long DNA more frequently and produces smaller DNA fragments than a restriction enzyme with a six-nucleotide recognition sequence.
A restriction enzyme with a four-nucleotide
Any given __________ occurs in DNA, on average, at a distance of 256 (4^4)nucleotides.
four nucleotide long recognition site
Any given _________________ occurs, on average, at a distance of 4096 (4^6) nucleotides.
six nucleotide long sequence
Any given __________________ occurs, on average, at a distance of 65536
(48) nucleotides.
eight nucleotide long sequence
allows scientists to extract and analyze bits of microbial DNA from samples, meaning they don’t need to find and grow whole cells.
PCR
is an essential element in DNA fingerprinting and in the sequencing of genes and entire genomes.
PCR
Basically, it’s like a technique to photocopy pieces of DNA. In a matter of a few hours, a single DNA sequence can be amplified to millions of copies
PCR
lets scientists work with samples containing even very small starting amounts of DNA.
PCR
The technique makes use of the DNA repair enzyme polymerase. This enzyme, present in all living things, fixes breaks or mismatched nucleotides in the double- stranded DNA helix. These breaks or mismatches could cause genes to malfunction if left unfixed.
PCR
Polymerase uses the intact half of the DNA molecule as a template and attaches the right nucleotides, which circulate constantly in the cell, to the complementary nucleotide at the site of the break. (DNA consists of two strands of nucleotide bases, which are represented as A, G, C, and T. In the laws of DNA base-pairing, A joins with T and G with C.)
PCR
Not all polymerases are created equal, however. Many fall apart in high heat.
PCR
PCR was developed in ______ following the discovery of an unusual heat-loving bacterium called ________ in a hot spring in __________
1985, Thermus aquaticus, Yellowstone National Park.
This bacterium’s polymerase, dubbed Taq, does its job of matching and attaching nucleotides even in the high heat generated by the successive_________ cycles required during PCR.
“photocopying”
______ made PCR possible.
Taq
_________: changing conditions - transient (S, X, growth rate), high initial substrate, different phases of growth.
Batch
________: steady-state, constant low concentration of substrate, constant growth ratethat can be set by setting the dilution rate (ie. the feed flow rate).
Chemostat
__________ is more efficient.·
Chemostat
____________ is more common.
Batch
CHOICE OF CONTINUOUS VS
BATCH PRODUCTION
Productivity
Flexibility
Control
Genetic stability
Operability
Economics
Regulatory
_________: rate of product per time per volume. Chemostat is better for growth-associated products. Wasted time in batch process.
Productivity
____________: the ability to make more than one product with the same reactor. Batch better.
Flexibility
___________: maintaining the same conditions for all of the products produced. In theory, the chemostat is better, steady state. In reality???
Control
____________: maintaining the organism with the desired characteristics. Chemostat selects for fast-growing mutants that may not have the desired characteristics.
Genetic stability
___________: maintaining a sterile system. Batch better.
Operability
____________: validating the process. Initially, many process batch, too expensive to re-validate after clinical trials.
Regulatory
Consider the production of a growth-associated product (like cell mass) in _________.
suspension culture
__________ of a chemostat is detrimental to engineered organisms.
Selective pressure
______ is more mechanically reliable.
Batch
________ system is more more flexible.
Batch
SPECIALIZED REACTORS
Chemostat with recycle
Multistage chemostat
Fed-batch
Perfusion
_________ under the control of an inducible promoter
Recombinant product
________ at the same rate if the recombinant product is not expressed.
Recombinant strain and wild type grow
If the __________is expressed, the _____________ grows much slower.
recombinant product, recombinant strain
First chemostat is fed with a non-inducing growth substrate, allowing the recombinant strain to be produced.
MULTISTAGE CHEMOSTAT
The effluent from the first chemostat feeds a second chemostat that is fed inducer, and the product is produced.
MULTISTAGE CHEMOSTAT
Note: new recombinant cells are continually added to the second chemostat not allowing take-over by a fast growing mutant.
MULTISTAGE CHEMOSTAT
_________ reactors gain some advantages of a CSTR, retain some disadvantages of batch
Fed-batch
Reduces substrate inhibition or catabolic repression, allows for high conversion, and the extension of stationary phase.
Fed-batch
______ nature usually leads to higher operation cost and batch variability.
Semi-batch
________ cultures are started as batch cultures and grown to an initial cell concentration
X, after which fed-batch operation begins.
Fed-batch
Substrate is consumed at the same rate it is added.
QUASI-STEADY STATE
Usually, fed-batch cultures are taken through many feedings cycles, with each feeding cycle followed by a harvest cycle during which the volume is drawn back down to V0 and the cycle begun again.
REPEATED FED-BATCH
PERFUSION CULTURE
Animal Cell culture
Constat medium flow
Cell retention
Selective removal of dead cells
Removal of cell debris, inhibitory by products
High medium use, costs raw materials and sterilization.
IMMOBILIZED CELL SYSTEMS
High cell concentrations
Cell reuse
Eliminates cell washout at high dilution rates
High volumetric productivities
May provide favorable microenvironment
Genetic stability
Protection from shear damage