Chapter 20: molecular genetics (Genetic engineering (Advantages to produce…
Chapter 20: molecular genetics
DNA molecules (Deoxyribonucleic acid - DNA)
are coiled tightly to form
Made up of
Complementary bases are bonded together by hydrogen bonds
Two anti-parallel polynucleotide chains make up a DNA molecule
Definition: a gene is a
unit of inheritance
born on a particular locus on a chromosome. It is a small segment of DNA that controls a
characteristics and the formation of a single polypeptide.
How are polypeptides/proteins made?
The region of DNA carrying the gene unwinds and unzips, the two DNA strands are separated
One of the DNA strands is used to make the mRNA, this strand is called the template
mRNA leaves through the nuclear pore
mRNA attaches to a ribosome
mRNA has no Thymine, instead it has
Ribosome reads the message in mRNA into a sequence of amino acids joined together to form a polypeptide
As the ribosome moves along the mRNA the polypeptide produced gets longer as more amino acids are formed
At the end of the mRNA strand, ribosome detaches and the polypeptide is released
NOTE: amino acids make up polypeptide, polypeptides make up protein
Definition: genetic engineering is a technique used to transfer genes from one organism to another. Individual genes may be cut off from the cells of another organism of the same or different species. The transferred gene can be expressed in the recipient organism.
Transferring the insulin gene
Obtain the segment of DNA in the human chromosome that contains the insulin gene. Cut the gene with a
. This enzyme cuts the restriction site at the two ends to produce
Obtain a plasmid from a bacterium. Cut the plasmid with the
same restriction enzyme
to the ends of the insulin gene.
Mix the plasmid and the insulin gene. The insulin gene will bind to the plasmid by
complementary base pairing
. Add DNA ligase to seal the gene to the plasmid. This is plasmid containing a gene from two different organisms is called a recombinant plasmid.
Mix the recombinant plasmid with a bacterium (eg E. coli). Apply
electric shock or heat. This opens the pores in the cell surface membrane of the bacterium for the plasmid to enter.
will use the new insulin gene to make insulin.
The insulin can be mass produced. It has to be extracted and purified before it can be used.
Pest resistant plants
Increased food production
Reduce environmental pollution as less pesticides are used
Insects may develop resistance to the poison produced by the genetically engineered plants
Death of other useful insects
Advantages to produce human insulin via this method
easier and cheaper to make in large quantities
identical to human insulin, hence does not induce allergic response
less risk of contamination compared to insulin from pancreas of animals
ethical concerns of vegetarians/religious groups can be overcomed
cheaper medicines (human insulin)
crops that produce toxins to kill pests= reduced usage of harmful pesticides
crops that can grow in extreme conditions= more food even in unsuitable conditions
improved nutritional quality of foods
vegetarians do no approve of animal genes in crop plants
GM food may cause allergies/be toxic or cancer-causing
deaths of useful insects=loss of biodiversity