genetic engineering

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outline the process involved in producing human in

1- the gene for human insulin is identified and isolated from human pandreatic cells.This can be done using restrction enzymes and an enzyme called reverse tanscriptase

2- A plasmid is cut open using the same restriction enzyme that we used to isolate the insulin gene

3-the insulin gene is inserted into the plasmid forming recombinant DNA

4- the plasmid is then taken up by bacteria and any transformed bacteria are identified using marker genes. The transformed bacteria are then grown in a fermenter- human isulin is produced as the bacteria grown and divide

5- the human insulin is extracted and purified so it can be used in humans 

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Advantages of using human insulin

  • it is identical to the insulin in our bodies - less risk of a reaction
  • it's cheaper and faster than animal insulin
  • overcomes any ethical or religious issues
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describe the process of producing golden rice

Golden rice is being developed to reduce vitamin A deficinecy.

1- psy gene and crtl gene are isolated using restriction enzymes. A plasmid is removed from the golden rice bacteria and cut open with the same restriciton enzyme. The psy and ctrl genes and a marker gene are inserted into the plasmif

2- a recombinant plasmid is put back into the bacterium 

3- rice plant cells are incubated with the transformed A tumerfaciens bacteria which infect the rice plant cells. A tumefaciens insets the genes into the plant cells DNA creating transformed rice plant cells.

4- the rice plant cells are then grown on a selective medium- only transforemd rice plants will be able to grow because they contain the marker gene that is needed to grow on this medium

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animals be genetically engineering for xeotranspla

Xeotransplation is the transfer of cells , tissues or organs from one species to another. It's hoped that xeotransplation can be used to provide animal doner organs for humans. However, rejection is more liekly as there is a greater genetic difference between two species.

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how are scientists trying to prevent organ rejecti

1-n inserting human genes

human genes for human cell surface proteins areinjectewd into a newly fertilised animal embryo. The genes intergrate into the aniamls DNA. The animal then produces human surface proteins which reduces the chance of transplat rejection

2- removing or deactivating animal genes

The genes for animal cell surface proteins are knocked out- they are removed or inactivated in the nucleus of an animal cell. The nucleus is then transferred to a inferterillised animal egg cell. The egg cell is then stimulate to divide into an embryo and the animal created does not produce animal cell surface proteins which reduces the risk of transplant rejection.

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discuss the issues surrounding genetic engineering

  • causes increaed antibiotic resistnance
  • GM crops may encourage farmers to carry out monoculture. Monoculture decrease biodiversity and could leave the whole crop vulnerable  to diseases, because the plants are genetically identical
  • genetically engineering animals for xeotransplation may cause them suffering
  • 'super weeds' which are herbicide resistnat may develop
  • biotehnology farmers may use GM crops to exploit famers in poor countries
  • illegal genetic engineering of humans
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define the term gene therapy

altering alleles inside cells to cure genetic disorders

somatic= altering alleles in body cells, particulary the cells that are most affected by the disorder. It does not affect the individuals sex cells so any offspring could still inherit the diseases

Germ line= involves altering the alleles in the sex cells. This means that every cell of any offpring produced from these cells will be affected by gene therapy and they won't suffer from the disease. Germ line therapy in humans is currently illegal.

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advantages and disadvantages of gene therapy

Advanategs

  • could prolong the lives of people with life threatening disorders
  • could give people with genetic disorders a better quality of life if it helps to ease the symptoms
  • Germ line therapy would allow the carriers of the genetic disorders to concieve a baby without that disorder
  • Germ line therapy could decrease the number of people that suffer from the genetic disorders and cancer

 Disadvantages

  • the body could identify vectors as foreing bodies and start an immune reponse against them
  • an allele could be inserted into the wrong place in the DNA, possibly causing more problems e.g. cancer
  • an inserted allele could be over exposed
  • disorders caused by multiple genes would be difficult to treat using this technique
  • the effects of treatment may be short lived in somatic therapy
  • it might be difficult to get the allele into specific body cells
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ethical issues surrounding gene therapy

  • people are worried meical treatment made may be used for cosmetics
  • very expensive - health service resources could be better spent on other treatments
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Outline the steps of DNA sequencing

DNA sequencing can be determined by the chain termination method - the method used to determine the order of bases in a section of DNA

1- a mix of single stranded DNA template, DNA polymerase, lots of DNA primer, free nucleotides and a fluorescenly labelled modified nucleotide nucleotide is added to four separate test tubes

2- tubes under go PCR which which produces many strands of DNA. The strands are different lengths because each one terminates out at a different point depending on where the modified nucleotide was added

3- DNA fragments in each tube are separated by electrophoresis and visualised under uv light. The complementary base sequence can be read from the gel. Each band after this represents one more base added so by reading the bands from the bottom of the gel upwards, you can build up the DNA sequence on base at a time

Nowadays sequencing is done in one tube in a automated DNA sequencer

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Describe genome sequencing

1- genome is cut into smaller fragments using restriction enzymes
2- the fragments are put into bacterial artificial chromosomes , these are man made plasmids. Each fragment is inserted into a different BAC
3- the BACS are then inserted into bacteria each bacterium contains a BAC with a different DNA fragment
4- the bacteria dived creating colonies of cloned cells that all contain a specific DNA fragment. Together the DNA creates a genomic library.
5- DNA is extracted from each colony and cut using retraction enzymes producing overlapping pieces of DNA
6- each piece of DNA is sequenced using the chain termination method
7- The pieces are put back in order to give the full sequence from that BAC
8- finally the DNA fragments from all the BACs are out back together in order by computers to complete the entire genome

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Comparing genomes

Comparing genomes of different species can help us understand evolutionary relationships we can tell how closely related different species are

Comparison within the same species can help illustrate early human migration. Can also be used to study the genetics of human disease. Also to develop medical treatments for a particular genotype.

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