Categories FAQ

Readers ask: Can you see any evidence to indicate that your samples of DNA?

Can you see any visible evidence to indicate that your samples of DNA were fragmented or altered in any way by the addition of EcoRl/Pstl? No. DNA is very small and fragmentation would be impossible to see. DNA molecules are negatively charged.

How do you know which sample has the smallest DNA fragment?

Lane 6 has the smallest fragment because it has a piece the furthest away from the top of the KB ladder. The further away you are from the top the smaller of a fragment you can have. Lane 2 and 4 have the largest because they have pieces closer to the top of the KB ladder.

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What caused the DNA to become fragmented?

DNA fragments. What probably caused the DNA to become fragmented? The chemical action of the restriction enzymes cutting at specific base. sequences.

How many DNA fragments do the crime scene and suspect DNA samples share?

DNA for the crime scene and each of the suspects; a total of six DNA samples.

How will we fragment the DNA samples in the lab?

Gel electrophoresis is a technique used to separate DNA fragments according to their size. DNA samples are loaded into wells (indentations) at one end of a gel, and an electric current is applied to pull them through the gel.

How do you determine the size of restriction fragments?

First, work out the frequency of occurrence of the restriction site as 1-in-x bases, as explained in the example for the Intermediate level calculation. Then take the size of the DNA in kb (kilobases) and multiply by 1000 to get the size in bases. Divide this by x and round to the nearest whole number.

What causes separation of DNA bands during electrophoresis?

To separate DNA using agarose gel electrophoresis, the DNA is loaded into pre-cast wells in the gel and a current applied. The phosphate backbone of the DNA (and RNA) molecule is negatively charged, therefore when placed in an electric field, DNA fragments will migrate to the positively charged anode.

What are DNA fragments called?

A restriction fragment is a DNA fragment resulting from the cutting of a DNA strand by a restriction enzyme (restriction endonucleases), a process called restriction. Restriction fragments can be analyzed using techniques such as gel electrophoresis or used in recombinant DNA technology.

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What is a restriction site in DNA?

A restriction site is a sequence of approximately 6–8 base pairs of DNA that binds to a given restriction enzyme. These restriction enzymes, of which there are many, have been isolated from bacteria. Their natural function is to inactivate invading viruses by cleaving the viral DNA.

Does a match of the suspect DNA fragments with the crime scene DNA fragments mean the suspect is guilty?

Using your DNA fingerprinting skills, you must determine who the criminal is. When the DNA samples are run through a gel, each sample will leave a specific pattern called a DNA Fingerprint. The pattern matching the crime scene DNA will belong to the guilty person.

How many fragments would result if the DNA above was digested with EcoRI?

3. You have a purified DNA molecule, and you wish to map restriction-enzyme sites along its length. After digestion with EcoRI, you obtain four fragments: 1, 2, 3, and 4.

How many pieces of double stranded DNA would result from this cut?

This causes the double strand of DNA to break along the recognition site and the DNA molecule becomes fractured into two pieces. These molecular scissors or “cutting” enzymes are restriction endonucleases.

What cuts up the DNA into tiny fragments?

In the laboratory, restriction enzymes (or restriction endonucleases) are used to cut DNA into smaller fragments. The cuts are always made at specific nucleotide sequences.

How are the DNA fragments separated by gel electrophoresis visualized and separated for use in constructing recombinant DNA?

The separated DNA fragments are visualized only after staining the DNA with the help of ethidium bromide followed by the exposure to UV radiation. The bright orange colour bands are shown. Then the elution is done, that is the separated bands of DNA are cut out from the agarose gel and extracted from the gel piece.

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What is used for DNA electrophoresis in the laboratory?

The gel used in gel electrophoresis is usually made of a material called agarose, which is a gelatinous substance extracted from seaweed. This porous gel could be used to separate macromolecules of many different sizes. The gel is submerged in a salt buffer solution in an electrophoresis chamber.

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