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Molecular Biology > Transgenic Plants > Flashcards

Transgenic Plants Flashcards

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1
Q

What are transgenic plants ?

A

These contain genes/gene which have been changed or inserted artificially

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2
Q

What are transgenic plants often called?

A

GM foods

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3
Q

What event revealed evidence of horizontal gene transfer?

A

A genome-wide analysis of millet and rice revealed the first clear evidence of horizontal gene transfer in plants (Monroe, 2005)

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4
Q

Why make transgenic plants?

A

To improve the growth characteristics & yield of agriculturally valuable crops

  • To increase the nutritional value of crops
  • To provide crops with resistance against:
    • insects
    • viral pests
    • drought
    • herbicides
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5
Q

What are the 3 steps in making transgenic plants?

A

Gene manipulation
Identify and isolate a gene that controls a trait of interest from another species
-Or create a new allele by modifying an existing gene

Gene introduction

  • introduce new gene into plants
    • direct DNA transfer (electroporation, micro injection, gene-gun)
    • Agrobacterium mediated gene-transfer

Selection and regeneration

- Plant is transformed (identified by a selectable marker)
- Transformed cell regenerates and transgenic plant is formed
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6
Q

What are the methods used in plant transgenesis?

A
  • protoplast fusion
  • Leaf fragment technique
  • Particle Bombardment technique
  • Chloroplast engineering
  • Antisense technology
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7
Q

Describe protoplast fusion

A
  • injured cells produce a mass of cells called callus over the site of wound
  • Callus cells are capable of forming shoot, roots or a whole organism
  • Callus can be made to contain new genes (reprogrammed)
  • Digest cellulose of callus or plant cells
  • fuse protoplast to protoplast from a different species

E.g. used to create broccoflower from broccoli and caulk form

Physical attributes of cauliflower, but has the color of the broccoli

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8
Q

Describe leaf fragment technique

A

Cut small discs from leaf and use genetically modified Agrobacter

Limitation is that Agrobacter can only infect dicotyledonous plants like:
-tomatoes

  • potatoes
  • apples
  • soybeans
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9
Q

Describe Particle Bombardment using Gene-gun

A

Shoot (blast) tiny metal beads coated with DNA into:

  • nucleus of:
    • embryonic cells
    • intact leaves
    • soft kernels
  • Chloroplast

Blast velocity
-about 430 meters/second

A marker, e.g. antibiotics is used to select only genetically transformed cells

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10
Q

Describe chloroplast engineering

A

Chloroplast DNA can accept several mew genes at once, unlike DNA in a cell’s nucleus

  • A high percentage of genes inserted into the chloroplast will remain active when the plant matures
  • DNA in chloroplast in separate from the DNA released in plant’s pollen
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11
Q

Describe Old Method of Cloning Multiple Genes

A

Two plants are produced, each on its own inserted gene

  • crossing by pollen transfer used to produce hybrid plant
  • Pollen can be transferred to other non-target plants and possibly beneficial insects
  • cauliflower mosaic virus (CaMV)
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12
Q

Explain Agrobacterium mediated gene-transfer

A

Genetic transfers occurs naturally in plants

  • When their wounds are infected by Agrobacterium tumefaciens(Agrobacter)
  • This soil bacteria contains a large double-stranded DNA molecule called a plasmid
  • This plasmid is also refferred to as tumor-inducing (TI) plasmid,
  • because it triggers an uncontrolled growth of the cells (tumor) in the plant
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13
Q

Explain using intermediate vectors to produce a transgenic plant with TI plasmids

A

An intermediate vector of manageable size is used to clone the segment of interest (gene)

  • the intermediate vector is then recombined with an attenuated (“disarmed”) Ti plasmid to generate a cointegrate structure bearing the insert of interest and
  • A selectable plant marker (kanamycin-resistance) between the T-DNA borders
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14
Q

Explain antisense technology

A

Polyglacturonase(PG)- an enzyme that digests pectin on the wall of the plant to induce normal decay

Agrobacter vector used to transfer the new gene that encodes the antisense mRNA molecule that unites with and inactivates the normal sense mRNA molecule for PG production

Antisense Technology also exploited for bruise resistant potatoe, and splicing genes for increased protein content from chicken into potatoes

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15
Q

What are reporter genes?

A

Used to monitor the function of any gene during development

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16
Q

What are the examples of reporter genes?

A
  • luciferase gene
  • bacterial GUS (b-glucuronidase) gene
  • bacterial lac(b-galactosidase) gene
  • jellyfish green fluorescent gene
17
Q

What are the luciferase gene?

A

A reporter gene(which is isolated from fireflies) which produces luciferase. Luciferase catalyzes the reaction of a chemical called Luciferin with ATP, in this process, light is emitted, which explains why fireflies glow in the dark. A transgenic tobacco plant expressing the luciferase gene also will glow in the dark when watered with a solution of luciferin

18
Q

What are the bacterial GUS (b-glucuronidase) gene?

A

Turns the compound to X-Gluc blue

19
Q

What are the bacterial lac(b-galactosidase) gene?

A

Turns X-gal blue

20
Q

What are jellyfish green fluorescent gene?

A

Which causes cells that express the GFP to glow green under blue light

21
Q

What are the advantages of plant transgenesis ?

A
  • Wealth of information on strains that can be exploited at the molecular level because plant breeding has a long history
  • Plants produce a large number of progeny. Therefore, rare mutations and recombinations can be discovered with more ease .
  • Plants’ regenerative capabilities is better than that of animals.
    • Many plants can regenerate from a single cell to form a genetic replica(clone) of the parent cell

-With plants, species boundaries and sexually compatibility are not issues

22
Q

What are the problems of plant molecular biology?

A

Molecular analysis of plants cells has lagged behind that of animal cells because:

  • Research priorities and allocation of federal funds to plant molecular biology aren’t high
  • Plants grow slowly and have relatively long generation times
  • Plants have large genomes. For instance, the haploid corn genome (15 billion base pairs) is about 5 times larger than the human genome
  • Plant cells are surrounded by a wooden box (cellulose cell wall), making them resistant to the introduction of foreign DNA)
23
Q

What are the current and possible benefits of GM/Transgenic plants?

A
  • increased productivity
  • Contribution to global food security/ elimination of hunger
  • Higher quality crops
    • tastier and healthier fruits
    • More valuable economics crops
24
Q

Contrast traditional and Flavr Savr

A

The Flavr Savr tomato ripens on the vine- resulting in the fuller flavor. It is modified so that it remains firm after harvesting

Ripe and increased flavor

The traditional tomato must be harvested while it is still green and firm so that it is not crushed on the way to the supermarket

Sprayed with ethylene after shipping to induce ripening

Ripe but decreased flavor

25
Q

Describe Pesticide Producing Plants

A

Bacillus thuringienisis (Bt): toxin= natural bacterial pesticide

Bt produces a crystallized protein (Bt toxin) that kills harmful insects and their larvae

  • For more than 35 years farmers used to spread Bt spores across their fields to protect their crops without using harmful chemicals
  • Plants have been engineered to contain and propagate the Bt gene
  • Setback- pollen produced by bioengineered corn could be deadly to monarch butterflies
26
Q

What are the disease resistant plants?

A

Genetic vaccines are used on a variety of crops:
-TMV resistant tobacco plant

  • Disease resistant Papaya plants, especially in Hawaii

Papaya ring spot potyvirus is a serious viral disease of papaya, which inhibits photosynthesis and stunts growth

27
Q

Explain how can GM be stored safely

A

Insects could infect crops during storage

Transgenic corn expressing avidin (a protein found in egg whites) is resistant to pests during storage

-Avidin blocks the availability of biotin. Biotin is a vitamin required by pests to grow

28
Q

Describe herbicide resistant plants

A
  • Traditional weed killers can also kill desirable plants
  • Glyphosate blocks an enzyme (EPSPS) necessary for photosynthesis
  • Crops can be genetically engineered to resist common herbicides like glyphosate
29
Q

Explain stronger fibers

A

Classical cross breeding was able to increase the average strength of cotton fibers by about 1.5% a year

-Plant transgenesis has helped create a strain with 60% stronger fibers- hence softer, more durable clothes for consumers and more profit for farmers

30
Q

Give an example enhanced nutrition

A
  • Improving public health, e.g. ‘golden Rice’
  • Golden rice genetically modified to produce large amounts of beta carotene- a provitamin that can be converted to vitamin A in the body- currently valuable in preventing blindness

Setback- the provitamin in golden rice must dissolve in fat to be used by the body

31
Q

What are the products in the pipeline for transgenic plants for pharmaceuticals ?

A

Transgenic plants that can manufacture pharmaceuticals

  • biproducts
    • Human growth hormone from transgenic tobacco plants
  • Vaccines e.g. transgenic tomatoes and bananas that produce hepatitis B vaccine
    • inexpensive
    • ease of administration -oral
    • ease of storage and delivery
32
Q

Describe the GM plants in pipeline

A
  • Oranges resistant to citrus canker
  • Disease-resistant sweat products
  • disease - resistant bananas

Pest and disease resistant cassava

Salt tolerant plants

Mercury resistant plants

Cold tolerant plants

Nicotine-free tobacco

Caffeine free plants

Industrial fibers

33
Q

Describe plant-based biochemical products

A
  • long chain polyunsaturates to reduce cholesterol foods
  • Aromatic components e.g. S-linalool enticing aroma from fresh tomato
  • Plant-based fuel, e.g. ethanol

Using Metwbolic Engineering -Biodegradable plastics

34
Q

What are the general concerns of GM foods?

A

Potential impact on human health

Potential impact on environment

Access and intellectual property

Labeling

Scientific protocol

35
Q

What are the ethical concerns of GM plants?

A
  • Violation of natural organisms intrinsic values
  • Tampering with nature by mixing genes among species
  • Comsuming animal genes in plants and vice varsa
36
Q

What are some organizations which regulate GM foods?

A
  • Institutional review board(SGU)
  • Grenada bureau of standards
  • USDA/FDA
  • CARICOM regional organization for standards and quality (CROSQ)
  • NIH
  • WHO
  • EPA
37
Q

Why should GM Foods be regulated?

A

Starlink episode in 2000 USA
-Generally modified corn meant as feed for animals ended up in grocery stores

In the U.S., the Institute of Medicine and the National Research Council released a report in 2004 that:
-Federal agencies should access any genetically altered food- regardless of whether it is developed by genetic engineering or by conventional cross-breeding

38
Q

What are the arguments for Crops?

A
  • Will eliminate world hunger
  • Create sustainable agriculture
  • Create more nutritious and tastier fruits/crops
  • Longer shelve lives
  • Cure diseases
  • Improve public health
  • Better output
  • Less input
  • Biofuels
39
Q

What are the arguments against GM foods?

A
  • Plant transgenesis is a young technology, not yet properly tested, effects not completely understood
  • poor regulations
  • genetic pollutions
  • genetic bio-invasion
  • increase pesticide use
  • damage to useful insects
  • creating seaweeds
  • food allergies
  • damage to food quality and nutrition
  • environmental damage
  • labeling issues
  • Socioeconomic hazards
  • May not end world hunger
  • Ulterior profit motives
  • Can companies be trusted

Molecular Biology (24 decks)

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