MANIPULATING GENOMES

Question 1

what is genetic engineering?

Answer 1

the transfer of genes from one organism to another

Question 2

state 3 advantages of genetic engineering

Answer 2

• producing medicines eg insulin
• using gene therapy to prevent diseases
• production of drought/disease resistant crops
• potentials for research

Question 3

state 3 disadvantages of genetic engineering

Answer 3

• long term health risks
• expensive
• may affect wild populations
• insect resistance in GM soya

Question 4

somatic cell gene therapy

Answer 4

• 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

Question 5

germ line cell gene therapy

Answer 5

• 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

Question 6

2 disadvantages of gene therapy

Answer 6

• short lived effects
• only used to treat genetic disorders caused by recessive alleles of a gene

Question 7

what is DNA sequencing?

Answer 7

identifying the base sequence of DNA fragments

Question 8

what 3 developments have DNA sequencing allowed?

Answer 8

• 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

Question 9

what is bioinformatics?

Answer 9

development of software that allows biologists to organise and analyse raw data

Question 10

what is computational biology?

Answer 10

using the data to build theoretical models to predict what will happen in unknown circumstances

Question 11

describe the process of genetic modification of bacteria

Answer 11

• 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)

Question 12

describe the development of DNA sequencing

Answer 12

• initially a slow process
• fully automated high throughput sequencing has rapidly increased the process speed

Question 13

describe the process of Sanger sequencing

Answer 13

• 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

Question 14

what is PCR?

Answer 14

polymerase chain reaction
- a method of amplifying DNA

Question 15

describe the process of PCR

Answer 15

• 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

Question 16

what is electrophoresis used for?

Answer 16

separating nucleotides

Question 17

describe the process of electrophoresis

Answer 17

• 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

Question 18

disadvantage of electrophoresis

Answer 18

only accurate enough to separate fragments that differ in length by only 1 base

Question 19

what are VNTRs?

Answer 19

variable number tandem repeats
- repeating sequences of nucleotides which appear next to each other

Question 20

what is DNA profiling?

Answer 20

determining genetic relationships / genetic variation by analysing cloned DNA fragments because the probability of individuals having the same VNTRs is very low

Question 21

which 3 areas are DNA profiling used in?

Answer 21

• 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

Question 22

describe the process of DNA profiling

Answer 22

• 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