Q3/ Outline the following topics: (a) The general properties of Restriction enzymes and their use in recombinant DNA.
Restriction enzymes are also known as restriction endonucleases, which recognise and cut a specific sequence of double-stranded DNA at that recognition sites. These enzymes protect the bacteria from foreign DNA (e.g. bacteriophages; Lamda phage), by digesting them into smaller pieces. The restrictive host protects its own DNA by a modification involving methylation of certain bases within DNA which constitute the recognition sequences for the restriction endonuclease.
Restriction Enzymes search for exact sequences of defined length, like 4 bp long (e.g., GTAC), some 6 (e.g., GAATTC), and still others 8 or more and their recognition sites are palindromes, or sequence which reads the same on both strands in the 5 ' --> 3 ' direction. Example, the site of recognition for HindIII is 5 'AAGCTT3 '. The arrows are the points at which the enzyme causes breaks in the DNA backbone and separating them by weakening the hydrogen bonds. This type of cut is staggered, which generates sticky ends because they are able to bind to a complementary single-stranded region. Restriction Enzymes can also produce fragments without single-stranded ends called a blunt cut, example by Eco RV, as shown below. Any DNA molecule, from viral to human, contains restriction-enzyme target sites purely by chance and therefore may be cut into defined fragments of a size suitable for
The goal of the restriction digests is to be able to cut the plasmids at specific sites. This step
Restriction enzymes are a tool that allows us to pinpoint human identity down to single differences in our DNA. Work through the following simulation so you can see these molecular scissors in action.
How to determine where the restriction enzymes, Ava II and Pvu II, sliced the DNA.
By restriction enzymes then amplified by polymerase chain reaction to make many to millions of copies of a single fragment.
Smallest will be found near the positive pole of the gel, as DNA is moving towards the positive pole, and small ones move faster. The large fragments will be found near upper half towards the positive pole, because the bigger size determines its slower speed moving towards the pole. Restriction fragment analysis, which specifies the DNA sequences, determines the size of the DNA
The first agarose gel provided insight into whether or not Zassy’s genomic DNA had been cut by the Sal I HF (NEB) restriction enzyme. As seen in Figure 1, Zassy’s cut DNA, in lane 3 left clear fragments between the 3 kb and 0.5 kb areas. Zassy’s uncut DNA, in lane 2, left a clear and bright band above the 10 kb marker. Therefore, the gel confirmed that Zassy’s DNA was successfully cut with Sal I because there was a significant difference the cut and uncut DNA that was run through the gel. There was an additional lane of cut DNA because another student adopted Zassy in the early stages of this experiment. Nevertheless, the clear distinction between lanes 2 and 3 allowed the experiment to continue on to purification of the DNA.
This however, was unsuccessful, as the restriction digestion created fragments of many different lengths, resulting in smears at different lengths on the gel electrophoresis due to the restriction enzyme recognition sites being present in-between the telomeric repeat sequences, the analysis was thus
After viewing the photograph of our gel, we had enough data to begin concluding on whether our unknown plasmid was pAMP or pKAN. Plasmid maps of pAMP and pKAN were given, informing us the number of base pairs each fragment contained when cut with a particular enzyme. After viewing the fragments of the three samples, we compared the data to the standard, lambda DNA fragments. For the lambda fragments, the number of base pairs for each fragment was given. With this data we were able to make a prediction on our unknown plasmid by comparing the length of migration of the standard fragments to the uncut, single cut, and double cut samples.
Restriction enzymes cut DNA at certain sites to create multiple DNA fragments. Restriction enzyme HindIII has known DNA fragment lengths and recognition sites when digesting lambda DNA, while the lambda DNA recognition site for restriction enzyme XhoI is unknown. The goal of this study is to determine the lambda recognition site of XhoI by comparing a HindIII digest and a HindIII and XhoI double digest on an electrophoresis gel. The HindIII digest had a band at 9.4 kb, but this band was not visible in the double digest, therefore we concluded the recognition site for XhoI was around 9.4kb. There were also two additional DNA
· Describe how a piece of foreign DNA can become a part of a plasmid that ends up altering the final phenotype of cells
In the case of AquAdvantage, they have done this with the Chinook Salmon gene and another gene from the Ocean Pout (the gene from the Ocean Pout has antifreeze proteins. They have inserted this into the gene sequence to allow the Atlantic salmon to grow during the winter months when wild Atlantic salmon stop growing). Restriction enzymes are enzymes which cut the gene from a specific recognition site and are used to extract the desired gene out of the DNA molecule. This gives the DNA “sticky ends” which will allow the sequence to later attach into a circular DNA plasmid. The growth hormone gene is then fused with a promoter such as a metallothionein gene, which allows the growth hormone gene to be produced throughout the body. The DNA fragment then goes through a process called ligation, which is where they are reassembled into a DNA plasmid. The sections of DNA with sticky ends are then joined together by base pairing in a process called annealing. If the ends were blunt, they would not properly attach and the engineered gene could fall apart, and they must have matching base pairs to connect too due to the base pairing rule that only certain bases join with certain bases. They
Furthermore, DNA is found in large quantities within the eukaryotic cell. Human cells alone have around 1000 times more DNA than typical bacteria [Alberts, c1989, p.23]. DNA, both on its own and with other molecules, plays a huge role in the making of an organism, from the importance of its chiral helical structure and its main functions, to the vast vicinity of error and inaccuracy that a small change to the genomic sequence can cause. It is the foundation upon which an organism is built and the main contributor to an organisms genotype and phenotype. But what are the constituents of DNA and can it
Plasmid DNA with Restriction Digest: The purpose of restriction digest of plasmid DNA is to understand how each DNA plasmids was cut with the given restriction enzymes and perform gel electrophoresis to observe the samples. Nine restriction digests were created, containing three digests for each of the three plasmid DNAs identifying as recombinant, non-recombinant, and unknown. Out of the nine digests, six are actual digests and three are undigested controls. A master mix is created to add to each of the nine samples with its following stock ingredients: 10 ul of 2X Reaction Buffer, 1 ul of Nco1, X ul of sterile water (Single digest), 10 ul of 2X Reaction Buffer, 10 ul plasmid DNA, 1 ul Nco1, 1 ul of Not1, and X ul of sterile water (Double
Did you know that with the science of DNA manipulation, animal cadavers can be turned into insulin for diabetics? Back in the 80's scientists isolated the human gene for insulin and transferred it into bacteria. Now bacteria cultures are used to produce large amounts of human insulin. DNA manipulation is especially important in medicine, where it holds the hope of curing genetic diseases such as Huntington's, and even some types of cancer. There are several major types of DNA-manipulation enzymes used by living cells. The first type is DNA polymerase, which cells use to replicate their own DNA. The next type is DNA ligase, which joins 2 pieces of DNA to create a single piece. The third type is restriction enzymes, which appear to be made only by bacteria. Restriction enzymes are very important enzymes that are vital to our manipulation of DNA (Rapoza, DNA, 2).
Restriction Enzyme Digestion – The experiment was begun after putting on gloves to avoid any chemical contact with the skin. Four microtest tubes were obtained, and each of them was labeled to contain the different enzymes or suspect DNA. Two of the microtest tubes were used for suspect one and the two different restriction enzymes, while two other microtest tubes were labeled for suspect two and the two restriction enzymes. After labeling the tubes, the contents that were at the bottom were taken out by slightly tapping them. Then to begin setting up the enzyme reactions, a micropipette was used to obtain 10 μL of the reaction buffer which was added to each of the four test tubes. The buffer is important because it carries the electrical current from the power supply in the gel. After the reaction buffer was in each, the microtest tubes were individually filled with their specific enzymes and DNA, shown in summary through Table 1.1 below. The restriction enzymes are used to cleave the DNA at specific