MANIPULATING GENOMES Flashcards
what is genetic engineering?
the transfer of genes from one organism to another
state 3 advantages of genetic engineering
- producing medicines eg insulin
- using gene therapy to prevent diseases
- production of drought/disease resistant crops
- potentials for research
state 3 disadvantages of genetic engineering
- long term health risks
- expensive
- may affect wild populations
- insect resistance in GM soya
somatic cell gene therapy
- functioning allele of a gene is introduced into a differentiated body cell which has faulty alleles
- the treated cells retain the faulty alleles so any offspring produced will still inherit the gene
germ line cell gene therapy
- engineering a gene in a sperm cell, ovum or zygote
- every cell in the growing individual has a non faulty copy of the gene
- offspring inherit new gene
2 disadvantages of gene therapy
- short lived effects
- only used to treat genetic disorders caused by recessive alleles of a gene
what is DNA sequencing?
identifying the base sequence of DNA fragments
what 3 developments have DNA sequencing allowed?
- genome wide comparisons between individuals / species to aid the study of evolutionary relationships
- predict genotype phenotype relationships
- development of synthetic biology to create artificial organisms
what is bioinformatics?
development of software that allows biologists to organise and analyse raw data
what is computational biology?
using the data to build theoretical models to predict what will happen in unknown circumstances
describe the process of genetic modification of bacteria
- DNA is isolated; restriction endonuclease cut DNA fragment at recognition sites and leave sticky ends
- the fragments are modified for transcription
- the DNA is inserted into a vector & ligase enzyme glues the sticky ends of the DNA and plasmid together with a phosphodiester bond which seals the sugar phosphate backbone & forms recombinant DNA
- the host vector must be fully permeable so ice cold solvent applied and then electric shock to increase permeability to plasmid uptake (electroporation)
describe the development of DNA sequencing
- initially a slow process
- fully automated high throughput sequencing has rapidly increased the process speed
describe the process of Sanger sequencing
- fragment mixed with excess nucleotides, DNA polymerase, primers & terminator bases
- heated to 95 degrees to separate DNA strands
- cooled to 50 degrees to anneal (primers bind to DNA)
- heated to 60 degrees so DNA polymerase can synthesise complementary strands
- read by ordering the fragments by size and recording the terminator nucleotide
- modified nucleotide is flurorescently labelled
what is PCR?
polymerase chain reaction
- a method of amplifying DNA
describe the process of PCR
- strand separation: heated to 95 degrees for 5 mins to separate the strands
- annealing: cooled to 55 degrees so primers can bind to complementary DNA site
- extension: heated to 72 degrees so that DNA polymerase can copy both strands of target DNA
- amount of DNA doubles each time
what is electrophoresis used for?
separating nucleotides
describe the process of electrophoresis
- glass plate with electrodes set up at each end
- agar on glass plate
- make wells at negative end and add buffer to control pH
- load dye into wells to make DNA visible, add DNA fragments which have been broken by restriction endonucleases
- connect to power supply
- smaller fragments move further and faster
- negative DNA is pulled to positive end
disadvantage of electrophoresis
only accurate enough to separate fragments that differ in length by only 1 base
what are VNTRs?
variable number tandem repeats
- repeating sequences of nucleotides which appear next to each other
what is DNA profiling?
determining genetic relationships / genetic variation by analysing cloned DNA fragments because the probability of individuals having the same VNTRs is very low
which 3 areas are DNA profiling used in?
- forensic science
- medical diagnosis of genetic diseases
- animal and plant breeding to prevent unwanted inbreeding in captive breeding, identify desirable characteristics or determine parentage of pedigree animals
describe the process of DNA profiling
- collection: select small sample of DNA from tissue and use PCR to amplify
- digestion: restriction endonuclease cut fragments called satellites at recognition sites through both DNA strands
- separation: electrophoresis, add alkaline to separate double strands and carry out southern blot where single strands are transferred to membrane
- hybridisation: DNA radioactive probes added to label fragments
- development: VNTRs and DNA transferred to nylon sheet exposed to UV/X ray
- analysis: the development of x ray film reveal dark bands where radioactive DNA probes have attached
