genetic revolution Flashcards
1
Q
how to make recombinant DNA
A
1) a section of DNA is snipped out of the DNA of one species
2) this is then inserted into the DNA of another species
3) this is called recombinant DNA
4) the organism that receives the new gene from a different species is transgenic
2
Q
what can a transgenic organism do
A
the organism receiving the new gene can now manufacture the protein that the new gene codes for
3
Q
what two sorts of DNA do bacteria have
A
1) DNA found in their bacterial ‘chromosome’
2) smaller circular pieces of DNA called plasmids
4
Q
what do bacteria naturally do
A
they naturally ‘swap’ plasmids
5
Q
what does transgenic bacteria use
A
plasmids
6
Q
what are plasmids
A
smaller circular pieces of DNA
7
Q
what enzymes are used in making transgenic bacteria
A
restriction endonuclease
DNA ligase
8
Q
what does restriction endonuclease do
A
an enzyme that cut DNA molecules at specific points
different restriction enzymes cut DNA at different places
they can be used to cut out specific genes from a molecule of DNA
9
Q
what does DNA ligase do
A
enzymes that join cut ends of the DNA molecule
10
Q
what does each restriction enzyme recognise
A
each restriction enzyme recognises a certain base sequence in a DNA strand - the recognition site
-> it will only cut if it recognises this sequence of bases
11
Q
what two type of ends can restriction endonuclease cut to produce
A
blunt ends
sticky ends
12
Q
how does the restriction endonuclease cut a blunt end
A
make a straight cut
13
Q
what are blunt ends
A
uniformed ends
no exposed bases
14
Q
how do some restriction enzymes cut to make sticky ends
A
make a staggered cut to produce fragments of DNA with overlapping ends
15
Q
what are sticky ends
A
overhangs of nucleotide bases that aren’t aligned with base pairing
-> plasmid overhang is complementary to DNA overhang
16
Q
why is it easier for sticky ends to be joined by DNA ligase than blunt ends
A
sticky ends have exposed bases
17
Q
how do you produce a transgenic bacterium (exam key points)
A
- cut out desired human gene using restriction endonuclease
- remove plasmid and cut using same restriction endonuclease
- mix and add DNA ligase to join together
- forms recombinant plasmid
- plasmid acts as a vector
- inserted/transferred back into bacterium to form transgenic bacterium
18
Q
safety when making transgenic bacteria:
A
- when using bacteria keep at 25 degrees celsius
-> bit less than optimum - no pathogenic bacteria
- seal with tape
-> allows oxygen to enter -> prevents anaerobic respiration (causing them to become pathogenic bacteria)
19
Q
what is a plasmid
A
- a small loop of DNA in bacterium that contains some genetic info
- independent of chromosomal DNA
20
Q
what type of gene do plasmids contain
A
- genes that give bacterium advantage eg. antibiotic resistance
- not an essential part of DNA coding
21
Q
what does restriction endonuclease do
A
cut DNA molecules at a specific point
22
Q
what does DNA ligase do
A
joins cut ends of DNA molecules -> forms sugar-phosphate backbone
23
Q
why do you need to cut out the gene and cut the plasmid open with the same restriction endonuclease
A
each restriction endonuclease recognises a specific base sequence
-> need to use same so you don’t cut desired gene up
-> complementary base sequence -> join them together
24
Q
what is a transgenic plasmid
A
has a gene from a different SPECIES
25
give an example of a gene that has been successfully inserted into bacterial plasmids
insulin
26
why are plasmids used instead of the main bacterial DNA
shorter -> not long bases -> easier to stick with restriction endonuclease
27
what are bacteriophages
- virus -> target bacterial cells
- act as vector -> mean of transferring a gene
28
how do bacteriophages attack bacteria
- it attaches to the cell wall of the bacterium and injects its own DNA into the bacterial cells
- the DNA becomes incorporated into the DNA of the host cell
- causes the production of many virus particles
29
how can bacteriophages be used for genetic modification
a foreign gene gets inserted into the DNA of the bacteriophages, the virus will inject it into the bacterium with its own genes
30
what is the issue in using bacteriophages in genetic modification
the virus injects all its DNA, including the gene wanted
-> all the DNA may not be wanted
31
example of uses of genetically modified bacteria
humulin -> given to diabetics who lack insulin
32
once they have been genetically modified, what happens to bacteria
they are cultured in fermenters
- replicate many times
- produce large quantities of product
33
achieve optimum conditions in fermenter:
- optimum temp -> probe to monitor, water jacket to maintain temp
- aerobic conditions -> aerator -> transfers oxygen in so respiration can occur to release energy so things can grow
- paddles distribute contents -> stops contents settling on bottom
- optimum pH -> using probe -> optimum conditions for growth
- prevent contamination -> filter -> traps pathogens and stops them entering
34
what to do before using a fermenter
sterilise
- no harmful bacteria
- reduce competition for nutrients
35
uses of genetically modified bacteria:
human vaccines
- makes antibodies against antigens and forms memory cells - immunity
- bacteria have been genetically modified to produce antigens of the hepatitis B virus
36
uses of genetically modified bacteria:
enzymes for washing powers
- bacteria have been genetically modified to produce enzymes that can digest
- many stains are biological
-> blood = proteins
-> grease = lipids
- enzymes can break down large insoluble molecules into smaller soluble molecules
-> then dissolve in water, removing stain
37
uses of genetically modified bacteria:
enzymes for food industry
- enzyme - glucose isomerase
-> converts glucose to fructose
-> fructose is much sweeter, so less is needed to sweeten food
-> save money + healthier food
38
uses of genetically modified bacteria:
human growth hormones
- pituitary gland may not produce enough growth hormone
-> leads to slowed growth
- can inject from genetically modified bacteria
39
uses of genetically modified bacteria:
bovine somatotrophin (BST)
- increases muscle production of bulls
- increases yield of milk produced by cows
- growth hormone in cattle
40
uses of genetically modified bacteria:
human insulin
- used to be extracted from pigs and cows
-> expensive and difficult to maintain constant supply
-> not as good
41
what type of person needs more insulin
type 1 diabetic -> means body stops producing insulin
-> more likely inherited
42
what is type 1 diabetes
a person whose pancreas cannot make the hormone insulin, which controls the amount of glucose sugar in the blood
43
if left untreated, what can diabetes lead to
can lead to blindness and can be fatal
44
what was one of the earliest successes in genetic engineering
the production of human insulin, using e.coli
45
before human insulin was made by genentically engineered bacteria, how was it made
the insulin was extracted from pancreases of pigs
this often led to eventual rejection of the pig’s insulin which is not quite identical to that’s of humans
disadvantages:
- expensive
- ethical concerns
- not effective at controlling blood glucose
46
how to genetically engineer insulin
1) get a human chromosome containing the insulin gene
2) use restriction endonuclease to cut the insulin gene out
3) use the same restriction endonuclease to cut the plasmid out from the bacterium
4) mix the plasmid and DNA fragment with the enzyme DNA ligase to produce recombinant DNA
5) mix the plasmid with e-coli (bacteria)
6) open the pores of the bacteria, by applying temporary heat or an electric shock to allow plasmid to enter
7) the bacteria can grow in huge numbers in a fermenter
47
explain the benefits of growing the genetically modified bacteria in a fermenter
monitor temp and pH -> provide optimum conditions -> maximise growth of bacteria/yield
48
why is it difficult to genetically modify plants
they are multicellular
49
what needs to happen for a plant to be genetically modified
every cell in the plant must receive the new gene
50
what are the two main stages of genetically modifying plants
- introducing the new gene or genes into plant cells
- producing whole plants from just a few cells
51
what is agrobacterium
pathogenic bacterium -> causes crown galls disease (tumours) -> enters through ‘wounds’ in plant stems or roots -> stimulates tissue growth in disorganised way
52
why is agrobacterium an idea vector
it regularly inserts plasmids into plant cells
53
what type of plants does agrobacterium affect
only affects dicotlyeaonous plants
-> means they have two embryonic leaves in seed
54
how to genetically modify plants using agrobacterium
1) cut out desired gene form another species using restriction endonuclease
2) remove plasmid from agrobacterium using same restriction endonuclease
3) mix and join together using DNA ligase to form a recombinant plasmid
4) obtain leaf discs from plant to be modified
5) float discs on liquid containing recombinant plasmids
-> some take up plasmids, becoming transgenic plants
-> grow to be plants with desired gene
55
what is an alternative method to agrobacterium
a gene gun
56
why would a gene gun be used instead of agrobacterium
agrobacterium doesn’t infect cereal plants
57
how does a gene gun work
- fires tiny pellets of gold coated with the DNA with the desired gene form another
- fired directly into plant tissue - in petri dish
-> have desired gene -> particles release DNA -> uptaken by plant
- in young tissue is used, uptake of DNA is successful
58
what does a gene gun allow the genetic modification of
cereal plants, tobacco, carrot, soybean, apple, oilseed rape, and cotton
59
why is gold/tungsten used for the pellets in gene guns
they are very unreactive with nature
60
advantages of genetically modifying rice to make golden rice:
- allows rice to make beta-carotene which is converted into vitamin A when eaten
-> improves eyesight
- saves the eyesight of millions of children in developing countries who have vitamin A deficient diets
61
advantages of genetic modification to make tobacco plants:
- tobacco and soybean plants modified to produce antibodies against infection
- other modified tobacco plants also produce hepatitis B antigens for vaccinations
62
examples of genetic modification of plants:
- maize and wheat resistant to insects
-> bigger crop yield
- plants resistant to herbicide
-> when plant is sprayed by herbicide, only weeds will be killed
- dough-resistant crops
-> advantages in poorer, hotter countries
63
advantages of genetically modifying plants
- extend shelf life
- increases resistance to a range of pests and pathogens
- resistance to herbicides
- frost resistance- anti-freeze genes in blood from arctic fish
- increased heat and drought tolerance
- increased salt tolerance -> idea of growing crops in sea so land space isn’t taken upon
- will all lead to increased yield of crop - increased profits
- more nutritious crops - better balance of proteins, carbohydrates, lipids, vitamins, and minerals
- some genetically modified oilseed rape plants could be used to produce biodegradable plastics and anti-coagulants - blood thinners, prolong clotting time
- hope to produce crops that allow nitrogen-fixing bacteria to form on roots. would mean that they could obtain nitrogen from the air and fix it into a more usable form. plants convert this to a protein which is used for growth
64
disadvantages of genetic modification of plants
- more expensive
-> golden rice - people can’t afford
-> companies making GM crops make them unaffordable for farmers in countries like India and the Philippines
-> small farms can’t compete with larger plants
- decrease in genetic diversity
- risk spread to other plants via pollination
65
why is it difficult to genetically modify animals
they are multicellular
-> every cell in the animal must receive the new gene
66
what is the most successful technique so far for genetically modifying animals
- cut desired gene using restriction endonuclease
- inject desired gene into a newly fertilised egg
- put egg into surrogate mother
- born and develops into an adult
67
benefits of genetically modifying animals
- increased production of a particular product .eg. milk
- production of low cholesterol milk
- increased resistance to disease and other parasites
- manufacture of human antibiotics
- manufacture of special medicinal products
- production of organs for transplantation - xenotransplantation (can grow an organ on another organism)
- animals can then be cloned
-> produce large number of animals, genetically identical
-> large production of useful products
68
what does xenotransplantation mean
transplanting organs from other animals into humans
69
why do transgenic pigs have less change of being rejected by humans (xenotransplantation)
they have been produced with genes that code for the main human ‘marker antigens’
70
what is a problem of transplanted organs and how can this be reduced
(in xenotransplantation)
- organ may carry pathogens and viruses - harmful to humans
- viruses can be ‘hidden’ in the DNA of the transplanted organs so can go without detection
- treatment with immuno-suppressant drugs could allow pathogens to reproduce
- ethical issues
71
advantages of xenotransplantation
- can produce organisms with new and useful features
- medical benefits
- useful for food production .eg. insect/pesticide resistance, fast growing animals, milk production
72
disadvantages of xenotransplantation
- can have unexpected harmful effects
- possible that transgenic bacteria could mutate and become pathogenic
73
how can we manipulate variation
- selective breeding
- cloning
- genetic engineering
74
what is a clone
a genetically identical copy of an organism
75
what do many organisms use cloning as
a natural method of reproduction
76
how do some plants and all bacteria reproduce
by copying themselves
-> natural way of being cloned
-> mitosis
77
what is a form of natural cloning
asexual reproduction
78
how can plants be cloned
by taking cuttings
-> artificial asexual reproduction
79
how is cutting used for cloning
cuttings are taken from plants with desirable phenotypes to ensure that the desired phenotype is retained
80
how to do cutting
1) take a side shoot from a plant (dip into rooting powder to encourage growth)
2) transport to compost
3) place in greenhouse, water and grow
-> warm to speed up growth
-> humid to minimise water loss from leaves
81
what process allows the stem to grow (in cuttings)
mitosis
82
what is the problem with cutttings
takes a long time to make lots of clones
83
process of micropropagation:
- remove tips and side shoots of plant - these are called EXPLANTS
- explants are placed on sterile agar medium that contains glucose, amino acids, magnesium, nitrates, growth hormone that encourage plant growth
- explants with shoots (callus) are transferred to another culture medium with a different balance of plant hormones which induce root formation (-> have roots -> anchorage)
- once explants have grown roots, they are transferred to greenhouse
-> control heat, light, humidity, CO2
- make lots of clones
84
advantages of micropropagation
- large numbers of genetically identical plants produced rapidly - commercial quantities of identical plants with desirable characteristics
- species that are difficult to grow from seed or cuttings can be propagated this way
- plants produced at any time of year
- large number of plants stored easily (kept in cold storage in early stages then propagated)
- genetic modification (eg. disease resistant) can be introduced into thousands of plants quickly after only modifying a few
- preserve rare species
85
disadvantages of micropropagation
- cuttings are all the same so all plants are genetically identical - there is no variation -> means that they are vulnerable to the same diseases and pests -> less adapted to changes
- recessive genetic diseases can become a problem
- there are also less alleles available for future selective breeding programmes - decrease in genetic variation
- more expensive and difficult than traditional cuttings -> need trained personnel
- no genetic variation - if disease/insect attack the crops, all destroyed (more susceptible to disease)
86
animal cloning process:
- remove egg cell from sheep A and remove nucleus - enucleated
- take mammary gland cell from sheep B and remove nucleus
- fuse nucleus (from mammary cell) and egg together using an electric shock
- divides via mitosis
- embryo forms
- put embryo into nucleus of surrogate mother
- offspring look like sheep B
87
what are transgenic plants
animals that have been given genes from another species
88
what have sheep been genetically modified to do
to produce several human proteins
-> secrete protein in their milk
-> can be used to treat emphysema and cystic fibrosis
89
how can (transgenic) sheep be made to produce human proteins
1) identity gene for the protein
2) remove gene from human DNA
3) cut open the DNA in a bacterium
4) add the human DNA to the bacterium’s DNA
5) put the bacterium’s DNA into fertilised egg cell of sheep
6) place the fertilised egg into a female sheep so it can develop into a lamb
7) when the lamb becomes an adult, it produces milk with the hormone
90
transgenic cows making proteins:
scientists have produced a cow those milk contains increased amounts of casein, a protein used to make cheese and other foods, and almost no beta-lactoglobulin, a component in milk whey protein that causes allergies
91
genetically modified rats and mice:
- genetically modified mice are used extensively in research as models of human disease
- obesity, heart disease, diabetes, arthritis, substance abuse, anxiety, aging and Parkinson disease
- more recently, they have been used to grow human ears using stem cells
92
use of genetically modified mice
this mouse glows green because is contains a green fluorescent protein taken from a glowing jellyfish
this could be used to mark cancer cells in human patients to follow their movement around the body
93
advantages of genetically modified firefly’s
- fireflies light up to attract a mate
- scientists have taken the gene that causes the light and inserted it into cancer cells
- the cancer cells then light up
- the light triggers a reaction that kills the cancer
- healthy cells are unharmed because they have no internal light source
94
advantages of transgenic animals
- only have to genetically modify one animal
- genetically identical offspring
- mass produces the protein/desired characteristic needed
- faster production of offspring
95
disadvantages of transgenic animals
- ethical disagreement
- evidence that animals may not be as healthy as normal ones
- new science - there are unknown consequences
