applications of genetics Flashcards
1
Q
what were the aims of the human genome project?
A
- determination of order of bases in human genome
- identification of genes
- mapping of positions of genes on chromosomes
- anonymous (but still concerns)
2
Q
what were the findings of the human genome project?
A
- fewer genes in human genome than expected
- more repeated segments in DNA than expected
- there is a very close relationship linking all living organisms
- enabled embryo screening and screening for adult-onset disorders (cancers, huntington’s, alzheimer’s, cystic fibrosis)
3
Q
what were the aims of the 100K genome project?
A
- sequencing genomes of 100,000 NHS patients
- not anonymous (concerns that come with this)
4
Q
what were the findings of the 100K project?
A
- improved accuracy of diagnosis
- enabled tailoring of treatments and better predictions of effects of drugs
- improved study of variation with human genome
5
Q
what are the ethical concerns with finding out results of genetic screening?
A
- embryo screening may provoke idea of choosing alleles to ensure specific characteristics of child
- debate when a condition becomes a characteristic
- discrimination/ social stigmatism
- who has ownership and/or access to genetic data
- effect on loved ones
- misuse of data (eg. hacking)
- lab errors leading to misidentification
6
Q
which methods of sequencing were used for the two genome projects?
A
- HGP: sanger sequencing (took long time, only sequenced short sections of DNA)
- 100K: next generation sequencing (sequences entire human genome in few hours)
7
Q
why may genetic counselling be needed when going through screening process?
A
- to make sure the patient is informed of all risks before making decision
8
Q
what other genome projects have been carried out?
A
- chimpanzee’s
- allows conclusions to be drawn about evolutionary relationships by examination of genomes
- may help with conservation of species in future
9
Q
why was the vector (mosquito) genome sequenced in attempt to find methods of controlling spread of malaria?
A
- mosquitoes keep becoming increasingly resistant to insecticides
- sequencing of genome allows scientists to develop chemicals that make them susceptible to chemicals again
- which therefore prevents transmission
10
Q
why was the parasite (plasmodium) genome sequenced when attempting to find methods of controlling malaria?
A
- parasite keeps developing multi-drug resistance
- sequencing allows development of more effective drugs (eg. quinine- disrupts parasites digestion of haemoglobin)
11
Q
what are stem cells?
A
undifferentiated cells that can divide to give rise to cells which can then differentiate into specialised cells
12
Q
what are the two types of stem cells?
A
- embryonic stem cells (ESC’s)
- induced pluripotent stem cells (iPSC’s)
- prefer 2. over 1. as fewer ethical issues and less chance of rejection as cells are coming from self
13
Q
what are the pro’s of stem cell usage?
A
- production is large-scale and quick
- produces genetically identical cells
- ESC’s can become any cell
- helps with lack of transplant
- large potential benefit
- ESC’s can clarify fundamental biological mechanisms
14
Q
what are the cons of stem cell usage?
A
- expensive and unreliable
- still a new science- unforeseen consequences
- inadvertant selection of disadvantageous alleles
- embryo has moral rights
- ESC’s not really justified as have other option
- may lead to human cloning
15
Q
what is gene therapy?
A
the treatment of a genetic disease by inserting a functional DNA sequence into the cells of someone who has defective alleles
16
Q
what are the two methods of gene therapy?
A
- somatic cell gene therapy
- germ-line gene therapy
17
Q
what is somatic cell gene therapy?
A
- replace faulty genes with correct copies in affected tissues of body (lungs, gut, reproductive organs)
- new gene can’t be inherited as only placed in somatic cells
- therefore can still pass condition onto children
18
Q
what is germ-line gene therapy?
A
- gene would be inserted into embryo or gametes
- all new cells formed would now contain new gene
- correction is inherited (more controversial)
19
Q
what are the pros of somatic cell gene therapy?
A
- relief of symptoms
- no need for medication
- prevents development of cancer
- doesn’t permanently change genome
20
Q
what are the cons of somatic cell gene therapy?
A
- more than one treatment required
- difficult to get gene to integrate into chromosome and function correctly
- genetic disorder can still be passed onto offspring
21
Q
what are the pros of germ-line gene therapy?
A
- children would be free of genetic disorder
22
Q
what are the cons of germ-line gene therapy?
A
- fear that it could be used to modify characteristics of child
- permanent modification= ethical issues
23
Q
what is DMD?
A
- Duchenne Muscular Dystrophy
- recessive
- sex-linked
- no cure- treatments available (drisapersen)
- caused by a deletion which introduces stop codon too soon, causing lack of structural protein dystrophin
- leading to wasting of muscles
24
Q
how does drisapersen work in treating DMD?
A
- complementary to mutated sequences
- uses exon skipping to acts as a ‘molecular patch’
- binds to mRNA, over exon with deletion
- makes it readable again as ribosome can’t translate it
- results in shorter, but more functional dystrophin
25
what is meant by the term 'transgenic'?
-organisms which contain DNA from another organism
26
what is meant by the term 'recombinant DNA'
when the DNA of an organism is formed from different organisms
27
summarise the process of genetic engineering
- isolation of gene in a DNA fragment
- insert DNA fragment into vector (plasmid of bacterium)
- transfer of DNA to suitable host cell
- identification of host cell that have taken up gene (gene markers)
- growth/cloning of transformed host cells
28
what should you do beforehand with the bacteria?
- treat with chemicals to destabilise cell walls
29
what is the role of restriction endonucleases?
- bacterial enzymes that cut DNA at short, specific and palindromic sequences
- isolates and cuts gene from a chromosome
- unpaired bases produce sticky ends as enzymes make staggered cut
- same enzyme also cuts and produces complementary sticky ends in plasmid DNA
30
what are the problems with using restriction endonucleases?
- hard to locate gene
- recognition sequence could happen to also be in the middle (as well as end) of gene- cuts at inappropriate point
- DNA contains many introns that bacteria can't recognise/cut- protein translated will have extra amino acids and may not be functional
31
what can be done before cutting the DNA from a chromosome to make the gene more functional when transferred into host cell?
- collect mRNA for the desired gene (at this point introns have been removed)
- convert mRNA into cDNA (copy DNA) using enzyme reverse transcriptase
- then use DNA polymerase to convert cNA to dsDNA (double-stranded DNA)
- this is then put into plasmid
32
why should we use reverse transcriptase for isolation of a gene?
- don't have problems of introns (cDNA is made from mRNA- has already been transcripted in nucleus and spliced)
- easier to locate gene
- gene won't be cut into non-functional fragments
- no need for post-transcriptional processing
33
how do we increase the chances of a bacteria taking up the recombinant plasmid?
- heat shock
- cool to 4oC
- quick heat to 42oC
34
what are the 3 possible results when transferring the recombinant plasmid to growing culture of bacteria?
1. no plasmid taken up
2. non-recombinant plasmid (where DNA ligase has just joined the plasmid back together)
3. recombinant plasmid
35
explain the use of genetic markers in identifying bacteria that take up the recombinant plasmid
- plasmids with genes for antibiotic resistance are used (ampicillin and tetracycline)
- back in first steps, use restriction endonuclease with recognition site in middle of tetracycline resistance gene
- therefore, tetracycline resistance gene will no longer work if recombinant plasmid is taken up
36
describe the experiment carried out using genetic markers
- have a master (control) plate with no antibiotics present
- transfer bacteria with sterile velvet (replica plating) to plate with ampicillin
- transfer to 3rd plate with tetracycline
- go back to master plate and collect wanted colonies (as colonies are in same positions on plate)
37
explain the results of the genetic markers experiment
- control plate shows all three types of bacteria
- ampicillin shows bacteria with recombinant and non-recombinant plasmid (ones without plasmid killed)
- tetracycline plate only shows non-recombinant plasmid (recombinant ones are killed as tetracycline resistance gene is non-functional)
- colonies that were on the ampicillin plate but not the tetracycline plate are collected
38
what is scaling up?
- growing desired colonies in a fermenter
39
what are the pros of recombinant DNA technology?
- large-scale production of complex proteins- no limit to amount produced
- no need to use extracts from mammalian organs
40
what are the cons of recombinant DNA technology?
- complicated so needs experienced staff and equipment
- £££
- synthesis of required protein may involve several genes which each code for a polypeptide
- treatment with restriction endos produces millions of fragments that cant be used
- not all eukaryotic genes can be expressed in prokaryotic cells
41
what are the concerns that come with recombinant DNA technology?
possible transfer of antibiotic resistance gene to human pathogens (due to ready exchange of genetic material between bacteria)
42
what is genetic modification used for?
- certain species of bacteria naturally attack damaged plants and stimulate growth of tumor
- scientists can replace tumor with useful genes
43
how are genetically modified crops produced?
- using technique to make GM bacterium (reverse transcriptase/ restriction endos)
- causes plants to form clumps of undifferentiated cells (stem cells)
- stem cells used to grow new plants
44
give 2 examples of GM crops
- tomatoes
- soya
45
what are benefits of GM crops?
- superior keeping qualities
- higher yield
- reduction in pesticide use (for ones engineered for resistance anyway)
46
what are the concerns that come with GM crops?
- reduction in biodiversity
- GM crops may be resistant to herbicides (eg. soybean)
- unknown effects of eating new proteins produced by crop
47
where can DNA profiling be used?
- human paternity testing
- forensic science
48
what are STR's?
- short tandem repeats
- blocks of repeated nucleotides in introns
- varied in length and are repeated different no.s of times (leads to variation)
- no. of STR's used to build unique fingerprint
49
what is an example of a STR?
- D7S280
- 'GATA' bases are repeated on human chromosome 7
- different alleles of this locus have between 6-15 repeats of 'GATA'
- more times repeated= longer DNA fragment
50
describe the method used in genetic fingerprinting
