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What is recombinant DNA

The DNA of two different organisms that have been combined by isolating genes, cloning them and transfer them into microorganisms. These microorganisms are then grown to provide a factory for the continuous production of desired proteins


What’s the resulting organism of recombinant DNA called

Transgenic or generically modified organism


What are the 5 stages of making a protein using DNA technology of gene transfer and cloning

1. Isolation - of the DNA fragments that have the gene for the desired protein

2. Insertion - of the DNA fragment into a vector

3. Transformation - that is, the transfer of DNA into suitable host cells

4. Identification- of the host cells that have successfully taken up the gene by use of gene markers

5. Growth/cloning - of the population of host cells


What are the methods toproduce DNA fragments

Conversion of mRNA using reverse transcriptase

Using restriction endonucleases to cut fragments containing the desired gene from DNA

Creating the gene in a gene machine, usually based on a known protein structure


How in a host cell are they able to synthesise DNA from their RNA

Using an enzyme called reverse transcriptase


Describe how reverse transcriptase is used to isolate a gene

1. A cell that readily produces the protein is selected

2. These cells have large quantities or relevant mRNA, which is therefore more easily extracted

3. Reverse transcriptase is then used to make DNA from RNA. This DNA is known as complimentary DNA (cDNA) because it is made up of nucleotides that are complimentary to the mRNA

4. To make the other strand of DNA, the enzyme DNA polymerase, is used to build up the complementary nucleotide me on the cDNA template. This double strand of DNA is the required gene


What enzyme defends bacteria from viruses by producing enzymes that fit up the viral DNA

Restriction endonucleases


Where do restriction endonucleases cut

At a DNA double strand at a specific sequence of bases called a recognition sequence


How are genes manufactured in a laboratory

1. The sequence that is required is designed

2. The first nucleotide in the sequence is fixed to some sort of support (a bead)

3. Nucleotides are added step by step in the correct order

4. Add protecting groups - make sure that the nucleotides are joined at the right points, to prevent unwanted branching

5. Short sections of DNA called oligonucleotides are produced.

6. Once they are complete, they are broken off the support and all protecting groups are removed.

7. The oligonucleotides can then be joined together to make longer dna fragments


What are the advantages of the gene machine process

Any sequence of nucleotides can be produced in a very short time and with great accuracy

Free of introns, and other non coding DNA, so can be transcribed and translated by prokaryotic cells


How can DNA fragments be made using restriction endonuclease enzymes

1. Some sections of DNA have palindromic sequences of nucleotides - consist of antiparallel bass pairs

2. Restriction endonucleases are enzymes that recognise specific palindromic sequences ( recognition sequences) and cut the DNA at these places

3. ( different restriction endonucleases cut at different specific recognition sequences, because the shape of the recognition sequence is complementary to the enzymes active site

4. Can then separate recognition sequences at either side of the DNA fragment you want using restriction endonucleases

5. The DNA sample is incubated with the specific restriction endonuclease, which cuts the DNA fragment out via a hydrolysis reaction

6. The cut can leave sticky ends - they can be used to bind the DNA fragment to another piece of DNA that has sticky ends with complementary sequences