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Background Information of Module 1
Background Information of Module 1
37
Biology
Undergraduate 3
01/20/2018

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Term
who discovered restriction enzymes?
Definition
Swiss microbiologist Werner Arber and Stuart Linn
Term
what did Werner Arber's daughter Sylvia call restriction enzymes?
Definition
"servants with scissors"
Term
Arber discovered restriction enzymes while...
Definition
studying a phenomenon known as host-controlled restriction of bacteriophages (also known at the time as host-controlled modification of bacteriophages).
Term
Bacteriophages
Definition
viral particles that invade bacteria and replicate their own DNA independently of the bacterial chromosomal DNA
Term
the basis for Arber discovering restriction enzymes
Definition
he wanted to know why bacterial phages did better in some strains of bacteria than others
Term
what Arber proposed before discovering restriction enzymes
Definition
he theorized that previous exposure to a particular bacterial strain somehow protected that phage from that bacterial strain

Arber also proposed that there were specific sites in the virus with unmodified genome where restriction occured
Term
Arber and Linn referred to the enzyme responsible for this "endonucleolytic scission" as...
Definition
endonuclease R, a name later changed to EcoB
Term
a restriction enzyme discovered in E. coli after Arber and Linn's research
Definition
EcoK
Term
HindII
Definition
enzyme discovered in another bacterial species that degrades foreign phage DNA but not the bacterial host's DNA
Term
restriction or recognition site
Definition
the actual nucleotide sequence of the specific site where a restriction enzyme cleaves
Term
significance of discovering restriction or recognition site
Definition
confirms Arber's hypothesis that restriction enzymes are extremely selective with regard to where they make their cuts
Term
how many restriction enzymes are there?
Definition
over 800
Term
how many restriction sites are there?
Definition
over 100
Term
length of restriction sites
Definition
most are 4-6 bases long
Term
most restriction sites are palindromic, meaning...
Definition
the sequence reads the same forward and backward
Term
how bacterial enzymes are named
Definition
first 3 letters of bacterium from which it was isolated, e.g., Eco for E. coli, fourth letter for particular strain, e.g., EcoB, and Roman neumerals for enzymes from the same strain, e.g., EcoBII
Term
the 3 categories of restriction enzymes recognized today
Definition
-type I
-type II
-type III
Term
type I restriction enzymes
Definition
they recognize specific DNA sequences but make their cut at seemingly random sites that can be as far as 1,000 base pairs away from the recognition site
Term
type II restriction enzymes
Definition
they recognize and cut directly within the recognition site
Term
type III restriction enzymes
Definition
they recognize specific sequences but make their cut at a different specific location that is usually within about 25 base pairs of the recognition site
Term
purpose of restriction enzymes
Definition
defense against invading viruses
Term
how bacteria protect their DNA
Definition
by modifying their own recognition sequences
Term
how bacteria modify their own recognition sequences
Definition
usually by adding methyl (CH3) molecules to nucleotides in the recognition sequences and then relying on the restriction enzymes' capacity to recognize and cleave only unmethylated recognition sequences
Term
how bacteriophages protect theirselves from restriction enzymes
Definition
bacteriophages that have previously replicated in a particular host bacterial strain and survived are similarly modified with methyl-labeled nucleotides and thereby protected from cleavage within that same strain
Term
the first major application of restriction enzymes
Definition
as a tool for cutting DNA into fragments in ways that would make it easier to study and, in particular, identify and characterize genes
Term
a second major use for restriction enzymes
Definition
as a device for recombining, or joining, DNA molecules from different genomes
Term
the goal of recombining, or joining, DNA molecules from different genomes
Definition
identifying and characterizing a gene or studying gene expression and regulation
Term
how scientists today separate DNA fragments
Definition
restriction enzyme digestion, followed by electrophoresis
Term
probe (genetic context)
Definition
a DNA or RNA molecule with a base sequence that is complementary to a DNA sequence of interest
Term
what a probe is used for
Definition
to identify where in the genome (i.e., on which fragment) the sequence of interest is located
Term
Southern blotting
Definition
1: DNA fragments electrophoretically separated
2: fragments transferred from gel to solid medium, or membrane
Term
what is done to the DNA fragments after Southern blotting?
Definition
3: probes are used to bind to the sequences of interest
4: membrane is washed to leave only the probes bound to the membrane
Term
autoradiography
Definition
technique used to detect radioactive probes after the membrane is washed
Term
blunt-end fragments
Definition
DNA fragments with no sticky ends
Term
cohesive or sticky ends
Definition
overhanging single strands of DNA on a DNA fragment
Term
DNA ligase
Definition
enzyme that can covalently bind complementary sticky-end fragments
Term
what the utilization of sticky ends and DNA ligase enables molecular biologists to do
Definition
create seemingly limitless combinations of recombinant DNA
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