Unit 5: Section 4

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3.5.8 Gene cloning technologies allow study and alteration of gene function in order to better understand organism function and to design new industrial and medical processes. Gene cloning and transfer Fragments of DNA can be produced by • conversion of mRNA to cDNA, using reverse transcriptase • cutting DNA at specific, palindromic recognition sequences using restriction endonucleases • the polymerse chain reaction (PCR). Fragments of DNA produced by any of the above methods can be used to clone genes by in vivo and in vitro techniques. In vivo cloning. The use of restriction endonucleases and ligases to insert a gene into vectors, which are then transferred into host cells. The identification and growth of transformed host cells to clone the desired DNA fragments. The importance of “sticky ends”. In vitro cloning. The use of the polymerase chain reaction (PCR) to clone directly. The relative advantages of in vivo and in vitro cloning. The use of recombinant DNA technology to produce transformed organisms that benefit humans. Candidates should be able to • interpret information relating to the use of recombinant DNA technology • evaluate the ethical, moral and social issues associated with the use of recombinant technology in agriculture, in industry and in medicine • balance the humanitarian aspects of recombinant DNA technology with the opposition from environmentalists and anti-globalisation activists. Gene therapy The use of gene therapy to supplement defective genes. Candidates should be able to evaluate the effectiveness of gene therapy. 3 GCE Biology for exams from June 2014 onwards (version 1.5) 32 Medical diagnosis The use of labelled DNA probes and DNA hybridisation to locate specific genes. Once located, the base sequence of a gene can be determined by • restriction mapping • DNA sequencing. Many human diseases result from mutated genes or from genes that are useful in one context but not in another, e.g. sickle cell anaemia. DNA sequencing and the PCR are used to produce DNA probes that can be used to screen patients for clinically important genes. The use of this information in genetic counselling, e.g. for parents who are both carriers of defective genes and, in the case of oncogenes, in deciding the best course of treatment for cancers. Candidates should understand the principles of these methods. They should be aware that methods are continuously updated and automated. Genetic fingerprinting An organism’s genome contains many repetitive, non-coding base sequences. The probability of two individuals having the same repetitive sequences is very low. The technique of genetic fingerprinting in analysing DNA fragments, that have been cloned by PCR, and its use in determining genetic relationships and in determining the genetic variability within a population. Candidates should be able to • explain the biological principles that underpin genetic fingerprinting techniques • interpret data showing the results of gel electrophoresis to separate DNA fragments • explain why scientists might use genetic fingerprints in the fields of forensic science, medical diagnosis, animal and plant breeding.

3.5.8 Gene cloning technologies allow study and alteration of gene function in order to better understand organism function and to design new industrial and medical processes. Gene cloning and transfer

Fragments of DNA can be produced by • conversion of mRNA to cDNA, using reverse transcriptase • cutting DNA at specific, palindromic recognition sequences using restriction endonucleases • the polymerse chain reaction (PCR).

Fragments of DNA produced by any of the above methods can be used to clone genes by in vivo and in vitro techniques.

In vivo cloning. The use of restriction endonucleases and ligases to insert a gene into vectors, which are then transferred into host cells. The identification and growth of transformed host cells to clone the desired DNA fragments. The importance of “sticky ends”.

In vitro cloning. The use of the polymerase chain reaction (PCR) to clone directly.

The relative advantages of in vivo and in vitro cloning.

The use of recombinant DNA technology to produce transformed organisms that benefit humans.

Candidates should be able to • interpret information relating to the use of recombinant DNA technology • evaluate the ethical, moral and social issues associated with the use of recombinant technology in agriculture, in industry and in medicine • balance the humanitarian aspects of recombinant DNA technology with the opposition from environmentalists and anti-globalisation activists. Gene therapy

The use of gene therapy to supplement defective genes.

Candidates should be able to evaluate the effectiveness of gene therapy.

Medical diagnosis

The use of labelled DNA probes and DNA hybridisation to locate specific genes.

Once located, the base sequence of a gene can be determined by • restriction mapping • DNA sequencing.

Many human diseases result from mutated genes or from genes that are useful in one context but not in another, e.g. sickle cell anaemia.

DNA sequencing and the PCR are used to produce DNA probes that can be used to screen patients for clinically important genes. The use of this information in genetic counselling, e.g. for parents who are both carriers of defective genes and, in the case of oncogenes, in deciding the best course of treatment for cancers.

Candidates should understand the principles of these methods. They should be aware that methods are continuously updated and automated. Genetic fingerprinting

An organism’s genome contains many repetitive, non-coding base sequences. The probability of two individuals having the same repetitive sequences is very low.

The technique of genetic fingerprinting in analysing DNA fragments, that have been cloned by PCR, and its use in determining genetic relationships and in determining the genetic variability within a population.

Candidates should be able to • explain the biological principles that underpin genetic fingerprinting techniques • interpret data showing the results of gel electrophoresis to separate DNA fragments • explain why scientists might use genetic fingerprints in the fields of forensic science, medical diagnosis, animal and plant breeding.

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