Exam 2 Flashcards
How do we name restriction enzymes?
Name derived from the phenomenon
of host-controlled restriction and
modification
What are Type I and Type II restriction
enzymes?
Type I REase: Recognize specific sequences in the DNA but does not cut adjacently to them
* Tracks along the DNA for a variable distance before breaking the DNA strand
Type II REase: Cut within (or immediately adjacent to)
specific target sequences and generate specific fragments
* Only some cut the DNA at a defined distance (only a few bases away) from the recognition site, Limited application
Can we tell the type of restriction enzymes based on the name?
No
What types of ends can be produced from restriction enzymes?
Sticky and blunt
What sequences can be recognized by
Type II restriction enzymes?
Specific short DNA sequences
What are palindromic sequences?
Spelled the same way forward as backward (eg. civic)
What phage groups exist?
tailless, head with tail (e.g., λ), filamentous (e.g., M13)
What are the most common viral vectors?
adeno-associated viral, adenoviral, lentiviral, retroviral
What are the key similarities and
differences between λ and M13 phages?
λ: All regulatory sites are known, not all essential for the phage to function (making it a good place to cut and insert gene of interest)
M13: Does not have non-essential gene, Produce single-strand DNA, Exist as both dsDNA & ssDNA in different phases of its replication cycle
Which phage has ssDNA and which has dsDNA? Are there others that have RNA instead?
M13, yes (MS2 and Qβ)
What is multiplicity of infection (MOI)?
Ratio of “agent” (phase) to “infection target” (cell), Average number of virus particles needed to infect
each cell
How is MOI calculated?
Agent/infection target
What is the MOI if 50 target cells were infected when 1000 viral
vectors were used?
20 = (1000/50)
What are plasmids?
Small, circular pieces of DNA that exist independently of the bacterial chromosome
In what organisms do plamids occur
naturally?
Occur naturally in many strains of bacteria and in a few types of eukaryotic cells, such as yeast
How are plasmids replicated?
Own origin of replication that allows it to be replicated independently of the bacterial chromosome
What types of plasmids exist in nature?
Episome– plasmid
that can integrate
into bacterial
chromosome
What is Conjugation, Transformation and Transduction?
Conjugation: transfer of DNA from a living donor bacterium to a living recipient bacterium by cell-to-cell contact
Transformation: bacterium takes up a piece of DNA floating in its environment
Transduction: A virus transfers chromosomal DNA fragment or a plasmid from one bacterium to another by a bacteriophage
How do we clone DNA into plasmids?
Insert pieces of DNA which are then copied as a part of the plasmid
▫ Pass on to the progeny when the cell replicates
▫ Ability to replicate in the host bacterium
Most, or all, of the enzymes and other products
needed already in the host cell
What are conjugative and non-conjugative plasmids?
Conjugative: Large, low copy # and stringent control of DNA replication (tied to host cell chromosomal DNA replication)
Non: Small, high copy # and
relaxed DNA replication
What are the typical elements of a
plasmid?
Origin of replication, selectable marker, cloning site, reporter genes, promoter, terminator
What are YACs and BACs? What are their advantages and disadvantages?
Used for cloning, can take in big inserts
Yeast artificial chromosomes (YACs): Inserts can be several hundred thousand to 2 million bp long
Bacterial artificial chromosomes (BACs): Inserts can be up to 300,000 bp long
their large insert sizes make them difficult to use in gene cloning and sequencing experiments. Therefore, libraries with smaller insert sizes are needed
How is LacZ gene used for selection?
Blue white screening
What color indicates successful result?
White
How is cI gene used for selection?
If disrupted: undergo lytic
cycle
What indicates success? (cl for selection)