Genetic engineering Flashcards
(32 cards)
What is genetic engineering?
Deliberate manipulation of genetic material to modify organism’s characteristics often involving gene transfer
What is recombinant DNA?
DNA altered to contain nucleotides from 2 different organisms
Outline the key stages in transfer of DNA between organisms?
1) desired gene identified and isolated
2) multiple copies of gene made using PCR
3) gene inserted into vector
4) vector delivers gene into cells in different organism
5) cells with new gene identified e.g using marker genes
6) cells with new gene cloned
What are the main methods of producing DNA fragments?
- making complementary DNA (cDNA) using reverse transcriptase and mRNA
- cleaving DNA from donor organism with restriction enzymes
Why is mRNA often used to create DNA fragments?
- cells contain lots of mRNA corresponding to active genes
- mRNA is easier to extract from cells than DNA
Outline how is mRNA converted into DNA fragments?
1) mRNA extracted from cells
2) mRNA reverse transcribed using reverse transcriptase enzyme and DNA nucleotides
3) makes cDNA strand identical to original DNA strand and cDNA isolated from mRNA strand
4) cDNA, free nucleotides, and DNA polymerase can then form other strand of DNA reforming desired gene
What is the role of restriction endonuclease enzyme?
Recognise and cut DNA at specific palindromic nucleotide sequences to isolate gene fragments
What are palindromic sequences?
Sections of DNA where nucleotide sequence reads same in opposite directions on antiparallel strands
Outline the process of restriction enzymes cutting DNA?
1) DNA incubated with chosen restriction enzyme
2) restriction enzymes identify palindromic sequences in DNA double helix and cut double-stranded DNA if recognition sequence is present
3) recognition sequences at either end of desired DNA fragment allow restriction enzymes to separate fragment from rest of DNA to obtain desired gene
4) enzymes cut target gene fragment out via hydrolysis reaction
5) different restriction enzymes cut at different sequences based on their active site shape
What are sticky ends and where are they often found?
Short overhanging sequences of unpaired bases that bind to other DNA fragments when inserted into vectors
cut DNA ends
What is in vivo cloning/DNA amplification?
Process of producing large quantities of a target DNA fragment in living cells
Outline how a DNA fragment is inserted into a vector?
1) vector cut open at specific site using restriction enzyme creating sticky ends
2) same restriction enzyme used to cut target DNA fragment creating complementary sticky ends
3) DNA ligase forms phosphodiester bonds between sugar and phosphate groups on 2 strands of DNA joining sticky ends of vector and DNA fragment together
4) newly formed combined DNA molecule known as recombinant DNA
Outline how recombinant DNA is transferred into a plasmid vector?
1) host cells treated to enhance uptake of plasmids that have recombinant DNA
2) e.g apply CA2+ and temp shifts can make bacterial membranes more permeable to plasmids
3) electroporation uses electrical current to make bacterial membranes more porous helping plasmids enter bacterial cells
Outline how recombinant DNA is transferred into a bacteriaphage?
1) viruses that infect bacteria
2) bacteriophages inject DNA into host bacterial cells during infection
3) phage DNA now carrying the recombinant DNA inserts into host’s DNA
Outline how marker genes can indicate which host cells took up recombinant DNA?
1) inserted into vectors alongside target genes
2) transformed cells cultivated on selective agar plates
3) only transformed cells display characteristics encoded by marker genes
4) transformed cells can be cultured to mass-produce target DNA fragment through cellular replication
What are some examples of genetic markers?
- marker gene for specific trait e.g antibiotic resistance ensures only transformed cells form colonies
- marker gene visible under UV light e.g green fluorescent protein (GFP)
- inserting marker gene within GFP gene inhibits fluorescence if it is successfully incorporated
- marker gene coding for enzyme altering colour of specific substrate
Why are crops genetically modified?
To become resistant to herbicides or insects as competition with weeds and insect pests can significantly reduce yields, impacting global food security
What are advantages of genetically modified crops?
- less labour than traditional herbicides and pesticides
- cheaper than traditional herbicides and pesticides
- herbicide-resistant GM crops allow use of herbicides to kill weeds without harming crop increasing yield
- insect-resistant GM crops less likely to be killed by pests increasing yield
- insect-resistant GM crops reduce need for pesticides benefiting environment
What are disadvantages of genetically modified crops?
- encourage monocultures reducing biodiversity
- herbicide-resistant GM plants may crossbreed with wild plants creating herbicide-resistant weeds
- loss of traditional crop varieties reduces genetic diversity making crops vulnerable to disease and climate changes
- non-target insects could be harmed by toxin coded for by insect-resistant GM crops
- insect pests may evolve resistance to toxin coded for by insect-resistant GM crops
What is pharming?
Involves production of pharmaceuticals and human medicines by inserting human genes into other animals
What are advantages of genetically modified farm animals?
- improves quality e.g. by enhancing disease resistance
- improves quantity e.g. by enabling year-round reproduction
- improves productivity e.g. through faster growth
What are advantages of pharming?
- enables mass production of rare treatments
- makes drugs more accessible
What are disadvantages of pharming?
- raises animal welfare concerns
- can lead to animals being viewed solely as commodities
What are advantages of genetically modified pathogens?
- offers potential treatments for diseases previously deemed incurable
- can produce essential medicines, antibiotics, and enzymes e.g insulin
- useful in creating vaccines
- facilitates creation of DNA libraries for research
