manipulating genomes

genetic engineering

describes a number of different processes for obtaining a specific gene and placing that gene in another organism

restriction enzyme

enzymes that recognise specific recognition sequences and cut DNA at these places 

• the enzyme makes two incisions, one through each of the phosphate backbones without damaging the bases 

ligase

an enzyme that joins sugar and phosphate groups in the DNA backbones, forming phosphodiester bonds after the chemical bonds between the enzymes are cleaved (cut through) 

recombinant DNA 

the name for DNA formed by joining together DNA from different sources 

sticky end

short, sing-stranded section of DNA that portudes from double-stranded DNA and has been cut by a restriction enzyme

transgenic organism

an organism that has been genetically engineered to include a gene from different species

plasmid 

small, circular, double-stranded DNA molecule separate from the main chromosome 

palindromic sequencing 

• sequences that read the same in opposite directions 

• have antiparallel base pairs 

• the restriction enzymes recognise specific palindromic sequences and cut the DNA at these places 

• the shape of the recognition sequence is complementary to an enzyme’s active site  

plasmid (genetic vector)

• the plasmid selected contains specific markers which reveal whether or not the foreign DNA has been incorporated successfully

viruses (genetic vector)

used to transfer genetic information to another cell by altering the viral DNA and then placing it into a virus particle

• the virus must be programmed to be disabled otherwise can cause problems

‘gene guns’ (genetic vector)

bombard tissues with DNA coated particles- the DNA is physically forced into the cell

• simple and widely used with plants

• low efficiency as there isn’t much successful uptake of DNA and physical damage to cells

denaturation (PCR) 

the mixture is heated to approx 95 degrees Celsius, breaking the hydrogen bonds between the two polynucleotide chains- similar to the unzipping of DNA 

annealing (PCR)

the temperature is lowered to around 50-65 degrees Celsius, allowing short pieces of single-stranded DNA (primers) attach to the complementary on the separated DNA strands

elongation (PCR)

• temperature is increased again to approx 72 degrees

  • DNA polymerase