Genetic engineering

Question 1

What is genetic engineering?

Answer 1

manipulation of the genomes

Question 2

What are the basic principles of genetic engineering?

Answer 2

• isolating a gene for a desireable characteristic in one organism
  
  • may be same species
• placing it into another organism, using a suitable vector

Question 3

What is a transgenic organism?

Answer 3

• a genetically modified organism
• organism that carries a gene fro another organism

Question 4

How is the desired gene isolated?

Answer 4

• most commonly
  
  • restriction endonucleases to cut the required gene
  • specific to a gene
• isolating mRNA
  
  • for desired gene
  • using reverse transcriptase to produce a single strand of complementary DNA

Question 5

What is a sticky end?

Answer 5

• restriction endonucleases often cut DNA strands unevenly
  
  • some cut with blunt end
• this leaving one fragment a few bases longer than the other strand
• with these regions with unpaired, exposes bases, are called sticky ends
• sticky ends make it easier to insert the desired gene into the DNA of a different organism

Question 6

What is the advantage of isolating the gene from mRNA?

Answer 6

• easier to identify the desired gene
• as a particular cell will make some very specific types of mRNA
• e.g. beta cells in pancreas make insulin, so produce lots of insulin mRNA molecules

Question 7

What is the most common vecotr

Answer 7

• most common vector in GE is plasmid
  
  • small circular molecules of DNA separate from the chromosomal DNA that can replicate independantly
• effective in producing GE bacteria

Question 8

What is recombinant NDA?

Answer 8

• once a plasmid gets into a host cell it can combine with the host DNA to form recombinant DNA

Question 9

What is a marker gene? What are they used for?

Answer 9

• plasmids that are used as vectors usually contian a marker gene
  
  • e.g antibiotic resistance
• this enables scientists to determine that the bacteria have taken up the plasmid,
  
  • by growing the bacteria in media containing the antibiotic

Question 10

How is a DNA fragment inserted into a plasmid?

Answer 10

• plasmid must be cut open
  
  • same restriction endonuclease as used to isolate the DNA fragment is used to cut the plasmid
• plasmid then has complementary sticky ends to the sticky ends of the DNA fragment
• once complementary bases of the two sticky end are lined up, DNA ligase froms phosphodiester bonds between the sugar and the phosphate groups on the two strands of DNA, joining them together

Question 11

What is the second marker gene?

Answer 11

• used to show that the plasmid contains the recombinant gene
• the marker gene is itself often placed in the plasmid by GE methods
• plasmid cut by restriction enzyme w/in marker gene to insert desired gene
• if DNA fragment inserted successfuly, the marker gene will not ufnciton

Question 12

Why is antibiotic resistance not used as a vector anymore? WHat is used instead?

Answer 12

• concerns about antibiotic resistance in GE organisms
• fluroesecence, or enzyme that causes colour change in a medium now used