GENE TECHNOLOGY (GENETIC ENGINEERING)

By the end of the topic you must be able to: describe the steps involved in the production of bacteria capable of synthesizing human insulin:• identifying the human insulin gene• isolating mRNA and making cDNA using reverse transcriptase• cloning the DNA using DNA polymerase• inserting the DNA into a plasmid vector using restriction enzymes and DNA ligase• inserting the plasmid vector into the host bacterium• identifying genetically modified bacteria using antibiotic resistance genes(markers)• cloning the bacteria and harvesting the human insulin;(b) explain the advantages of treating diabetics with human insulin produced by gene technology

Defination of terms

ChromosomeDNAGene

DNA (DeoxyriboNucleic Acid)

-DNA is the genetic material of a cell. - It’s found in the nucleus.-It is organized into thread like structures called chromosomes.

Structure of DNA- Made up of small units called nucleotides

• Structure of nucleotide

There are four organic bases- Adenine (A)- Guanine(G)- Cytosine (C)- Thymine (T)

Nucleotides form a strand

- DNA has two strands that coil around each other like a twisted ladder. This is called a double helix.- Bases on one strand pair up with bases on the other strandA-T C-G. - These are called complementary base pairs.

Gene- This is a section of DNA that codes for a protein.- The sequence of bases on DNA determine the type and order of amino acids in a protein.

• Genetic modification is also known as genetic engineering.

• Genes from one organism are transferred to the set of genes (the genome) of another unrelated organism.

• Transgenic- means the transfer of genes from one organism to another of a different species

• An organism that contains a gene from another species is called a transgenic organism.

• Enzymes used in genetic modification• Restriction endonuclease• An enzyme that cuts DNA at specific sites. • The two ends of the cut DNA have a natural affinity and are called

sticky ends.• DNA ligase• An enzyme used to join pieces of DNA• Vector• Either a plasmid/bacterium or virus, it’s used to carry the desired

gene into the organism to be genetically modified.• Note: after inserting the new gene into a plasmid, the plasmid is now

called recombinant DNA.

Structure of a bacterium

General summary of the process of genetic modification

Genetic modification of bacteria to produce insulin

• Note: The outcome of genetic modification are new varieties of organisms, mostly but not exclusively of micro-organisms.

• Micro-organisms are preferred simply because they are easier to modify.

• Gene technology has important applications in biotechnology, medicinal drug production (pharmaceuticals industry), gene therapy, agriculture and horticulture.

This technique is used to manufacture• Enzymes for washing powders, food industry.• Human growth hormone.• Human vaccines• Bovine somatotropin (BST) used to increase

milk yield and meat production.

• Genetic engineering generates many potential benefits for humans, but there are potential hazards, too.

• The economic advantages may be out-weighed by environmental and ethical drawbacks or dangers.

Questions• The diagram below shows part of a DNA

molecule. It consists of two strands linked by aseries of paired bases.

(a) (i) The bases in DNA are adenine (A), cytosine (C), guanine (G) and thymine (T).

Complete the diagram above by writing in the correct base to complete each pair.

(ii) The DNA molecule is known as a double helix. Explain what is meant by the term ‘double helix’.

(b) Genetic modification (genetic engineering) uses enzymes to cut and join sections of DNA.

(i) Name the enzyme used to cut DNA at a specific site.(ii) Name the enzyme used to join two sections of DNA.(iii) What name is given to an organism that has been

genetically modified to contain DNA from a different species?

(c) (i) Name one human hormone that is produced by genetically modified bacteria.

(ii) Give one advantage of using genetically modified bacteria to produce this hormone.