Special enzyme termed border enzymes have been uncovered in countless different bacteria and also other single-celled organisms. These restriction enzymes space able to scan follow me a length of DNA in search of a certain sequence that bases that they recognize. This recognition site or sequence is typically from 4 come 6 basic pairs in length. As soon as it is located, the enzyme will attach to the DNA molecule and also cut every strand that the double helix. The restriction enzyme will proceed to do this follow me the full length the the DNA molecule which will certainly then break into fragments. The size of these fragments is measured in base pairs or kilobase (1000 bases) pairs.

You are watching: What do the bands on a restriction map show

Since the acknowledgment site or sequence of base pairs is recognized for each restriction enzyme, we can use this to form a detailed analysis of the sequence of bases in certain regions that the DNA in i beg your pardon we are interested.

In the presence of certain DNA fix enzymes, DNA pieces will reanneal or stick themselves to other fragments with reduced ends that are free to your own end sequence. The doesn’t matter if the fragment the matches the cut end originates from the exact same organism or native a various one. This ability of DNA to repair itself has been utilized by researchers to introduce international DNA right into an organism. This DNA might contain gene that permit the organism to exhibit a brand-new function or process. This would incorporate transferring gene that will result in a readjust in the nutritional quality of a crop or perhaps permit a plant to prosper in a region that is colder than that is usual desired area.

In this experiment, we will usage restriction enzymes to cut up DNA native a tiny virus referred to as Bacteriophage λ. This virus is 48,502 base pairs in length which is very small compared v the human being genome of approximately 3 billion base pairs. Because the whole sequence of λ is currently known we deserve to predict where each restriction enzyme will cut and also thus the expected size of the pieces that will certainly be produced. If the virus DNA is exposed come the limit enzyme for only a short time, then no every restriction website will be reduced by the enzyme. This will an outcome in pieces ranging in size from the smallest possible (all sites room cut) to in-between lengths (some that the sites are cut) to the longest (no sites are cut). This is termed a partial border digestion.

In this experiment, we will carry out a complete restriction digestion. ~ overnight digestion, the reaction is stopped by addition of a loading buffer. The DNA pieces are be separate by electrophoresis, a procedure that requires application of an electric field to cause the DNA fragments to migrate into an agarose gel. The gelatin is climate stained v a methylene blue stain to visualize the DNA bands and may it is in photographed.

This laboratory will certainly take about 3 days. The restriction digestion takes place overnight and also can be maintained in the freezer till the following class duration when it will certainly be be used for gel electrophoresis. The gels may be stained overnight before photographing or record results.


Understand what a DNA border enzyme is and also how it works. Learn to usage a micropipette. Find out to separate DNA on one agarose gel making use of electrophoresis. Understand just how to use a restriction digestion map to recognize a sample DNA. To compare the λ DNA bands ~ above a gel to the recognized λ DNA limit map.


For each lab team

Four microtubes Microtube rack 20-µl micropipette (or 10-µl micropipette) and sterile tips Waterproof pen manufacturer or foam cup v crushed ice cream for the adhering to 20 µl of 0.4 µg/µl λ DNA 2.5 µl BamHI limit enzyme 2.5 µl EcoRI limit enzyme 2.5 µl HindIII restriction enzyme10 µl distilled water Gloves 500-ml beaker (day 2) Electrophoresis room (day 2) strength supply (day 2) 20 µl 10X loading dye (day 2) 1.0% agarose gel (day 2)

Common Materials

Container through TBE systems (1X) 37°C water bath w/ floating rack 60°C water bath or saucepan on a warm plate (day 2) Cooler through crushed ice Freezer (non frost-free, if possible) Camera if wanted Distilled water 0.002% methylene blue stain (day 3)

Advance Preparation

Day 1: If you conserved the 1X TBE equipment from the gel Electrophoresis with Dyes activity, reuse it for this laboratory. Acquire enough crushed ice and also ice containers (styrofoam cups) for each laboratory group. Fill a pan through water and change it to 55°C ~ above a hot plate fill a second pan through water and adjust it to 37°C top top a warm plate while the students complete preparation the the restriction digests. Reconstitute the lambda DNA v sterile distilled water to 0.4 µg/µl. Aliquot lambda DNA, enzymes and loading dye because that each group and also keep in freezer till needed. Make the 1.0% agarose gel equipment as follows: To do 100 ml of gel, which is sufficient for 3 gels, sweet out 1.0 g that agarose and also place into a 200- to 250-ml glass beaker or flask. Include 100 ml that 1X TBE (Tris-Borate-EDTA) buffer. Warm in the microwave because that 30 seconds at a time, shaking gently every time, till the agarose is fully melted. Alternatively, the solution have the right to be heated on a hot plate, through occasional gentle shaking, until the agarose is melted. Keep heat if the class will usage it within a half hour. Otherwise, enable the equipment to cool and solidify. Cover and keep in the refrigerator. Day 2: Fill a pan through water and readjust it to 60°C. Pour enough agarose gels for each lab group as follows: undertake gloves Microwave or warm the agarose party in a warm waterbath till the gel liquefies. Be sure to usage a microwave designated because that science purposes (not food). Steady seal the ends of the gelatin tray making use of labeling tape. Location the plastic comb in the slot close come the finish of the tray. Pour about 35-40 ml the agarose into each gel tray. This will an outcome in a thick gelatin so that at least 20 µl that sample can be loaded right into each well. Permit cool till solidified (approximately 15 minutes). If storing overnight, location trays in a container or ziploc baggie through 0.5X TBE solution so they carry out not dry out. Job 3:Remove student gels native the refrigerator. Set up containers because that staining in a common area near a sink.


Gels might be discarded in continual trash receptacle. A summary of how to use a micropipet can be uncovered in activity 2 - gelatin Electrophoresis the Dyes.

Use the Methylene Blue:

Although methylene blue dye is not as sensitive together ethidium bromide it may be supplied to stain the higher quantities the DNA that are used in this experiment. Methylene blue is non-toxic yet will stain clothes, hands, and also equipment, so constantly wear gloves. Use the stain close to a sink and clean up spills immediately. Use distilled or deionized water come de-stain gels. Just use deionized water for making the 0.1X TBE buffer to do this stain due to the fact that the high chlorine levels of most tap water will damage the DNA. A solitary container that methylene blue dye must be all that is needed since it might be reused several times and also disposed of under the sink.

Use of power Supplies

See description in gel Electrophoresis of dyes - task 2Enzymes

Restriction enzymes require special treatment for handling and also use. Lock lose task unless maintained frozen; exposure to warmth temperatures for even a quick time will an outcome in lose of activity.

Using good sterile technique, aliquot samples for students, being careful to keep whatever on ice cream until ready to be used.

Enzymes should be stored in a foam container in the freezer (non frost-free if available), together with the unique buffer because that each enzyme. The distinct buffers save on computer the salt and also pH requirements for optimal activity of every enzyme.

Lambda (λ) DNA:

The λ DNA provided in this laboratory can exist as either a direct or one molecule, producing some confusion as soon as interpreting border digest results. By heating the sample to 60°C for 3 minutes, immediately prior to electrophoresis, the hydrogen bonds holding the end of the direct DNA with each other in a circle will be broken.

Background Reading

Since viruses have actually a relatively simple genome, scientists have actually studied your DNA and used this details to test theories and develop principles that use to the genes of living organisms. Among the most studied viruses is referred to as bacteriophage lambda (λ). Bacteriophage λ is a virus that infects bacter cells.

Student Activity: restriction Enzyme evaluation - Methylene Blue stain


Background Reading

Bacteriophage λ is a virus that attacks bacterial cells and is one of the many studied viruses. The details from the reasonably simple virus genomes has actually been offered to test theories and also develop ideas that use to the genes of life organisms. The DNA of bacter λ is about 48,514 base pairs or 48.514 kilobase pairs in size while the human genome is roughly 3 billion base pairs.

This experiment provides special “restriction” enzymes the act together chemical scissors to reduced λ DNA into pieces. Every enzyme establish a distinct sequence of 4-6 bases along the DNA strand and cuts the strand at these sites - the first step in a process called border mapping. These smaller, details sections of one organism’s DNA deserve to then be learned in detail and also an synopsis of the totality genome deserve to be constructed. This procedure is one of the most vital in modern biology.

The little fragments the DNA are separated by gelatin electrophoresis. The motion of the pieces will constantly be in the direction of the hopeful electrode since DNA is a negatively fee molecule. The fragments move v the gel at a price that is figured out by their size and shape, through the smallest relocating the fastest.

DNA cannot be viewed as it moves through the gel. A loading dye must be added to each of the samples prior to it is pipetted right into the wells. The progress of the dye deserve to be watched in the gel. It will certainly initially show up as a blue band, at some point resolving into two bands of various colors.

The much faster moving, purplish tape is bromophenol blue dye the migrates at roughly the same rate as a 300 base pair fragment that DNA. The slower moving aqua band is xylene cyanol, virtually equivalent come a 9000 basic pair fragment. The faster moving band must relocate at least 4-7 centimeter from the wells to accomplish the best separation of DNA because that analysis. Treatment should it is in taken no to allow the bromophenol blue band operation off the finish of the gel.

Following staining to find the DNA, the gel is observed and the fragments show up as a sample of bands. In this experiment, we will compare our banding pattern v a predicted an outcome shown in figure 1.

Figure 1. Lambda DNA restriction digest (Photo native J. Leach Laboratory)

Information may be detailed by her teacher the details the procedure of isolating and examining these bands to produce a DNA fingerprint.

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Understand what a DNA border enzyme is and how the works. Discover to usage a micropipette. Discover to different DNA on one agarose gel making use of electrophoresis. Understand how to usage a restriction digestion map to determine a sample DNA. Compare the λ DNA bands on a gelatin to the well-known λ DNA restriction map.


For each lab group

Four microtubes Microtube rack 20-µl micropipette and sterile advice Waterproof pen 250 µl distilled water Gloves 20 µl 10X loading dye (day 2) 1.0% agarose gelatin (day 2) manufacturer or foam cups v ice because that each that the following: 20 µl that 0.4 µg/µl λ DNA - save in cup of ice 2.5 µl BamHI limit enzyme - save in cup of ice cream 2.5 µl EcoRI restriction enzyme - keep in cup of ice 2.5 µl HindIII limit enzyme - store in cup of ice500 ml beaker (day 2) fancy lab tape (day 2) Common Materials Electrophoresis chamber (day 2) strength supply (day 2) Container v TBE buffer (1X) 37°C water bath w/floating rack 60°C water bathtub w/floating rack Cooler through crushed ice Freezer (non-frost-free, if possible) Distilled water 0.002% methylene blue stain (day 3) Stain container (day 3)


The methylene blue dye will stain skin, clothes, and also equipment. Constantly wear gloves and safety glasses. Carry out all staining in a main area close to the sink.


Put on gloves. Store all enzyme and DNA aliquots on ice cream through action 6. Label 4 microtubes, reagents as indicated below, and also place castle in the pipe rack:
10X buffer4 µl4 µl4 µl4 µl
DNA4.0 µl4.0 µl4.0 µl4.0 µl
BamHI2.0 µl000
EcoRI02.0 µl00
HindIII002.0 µl0
Water30.0 µl30.0 µl30.0 µl32.0 µl


Set the micropipette to 4 µl and carefully include 4 µl the 10X border buffer to every tube. When adding the droplets the buffer come the border tube, touch the pipette pointer to the bottom that the tube. Use a new tip for each buffer. Collection the micropipette to 4.0 µl and also carefully add 4.0 µl the DNA to every tube, utilizing a brand-new tip every time. Add 32.0 µl the distilled water come the regulate tube and also 30.0 µl come the various other reaction tubes. Nearby the microtubes and also heat in a 55°C waterbath for 10 minutes then instantly place on ice cream for 2 minutes. Add 2 µl of the ideal restriction enzyme come the reaction tube as suggested on the grid. Use a new tip for each enzyme added. Nearby the microtube caps and make sure that every the liquid is in ~ the bottom that the tube by tapping the bottom of the pipe gently on the workdesk top. Provide the tubes come the instructor. They will certainly be incubated in ~ 37°C overnight. The tubes will then be frozen till the next class (up to 2 months).