L26 - Genetically modified plants Flashcards
(15 cards)
how did we modify plants pre-mendel
selectring plants based on physical cahrecteristics
= wantsed features - big leaves
when was sanger-sequencing first invented
1977
what is cross breeding
crossing plants of same species or closely related
what is hybrid breeding
croissing plangts of different species to produce ‘hybrids’
what is mutation breeding
using physics/ or chemical agents to create mutations to ‘speed up’ natural selection
what is molceular breeding
DNA markers linked to specifc traits to help in slecting for desired characteristics
name the 2 ways to genetically mody plants
Agrobacterium tumefaciens
= natural genetic engineer
Particle bombardment = biolistics method
what is agrobacterium tumefaciens
soil bacteria that naturally transfers DNA into plant cells
= Scientists hijack this system to introduce desired genes into plants
describe the plasmid of agrobacterium tumefaciens that allows it to be used for gene modifying of plans
Agribacterium tumefaciens contains a Tumour inducing (Ti) plasmid
T-DNA region in the plasmid contains enzymes that stimulate cell proliferation
= this region is cut out and inserted into plant cells genome when bacteria infect
by CHANGING the DNA in the T-region for our gene of interest we can naturally cause genetic modifications
describe steps in how agrobacterium tumefaciens is used for gene modiying in plant cells
- Ti plasmid and gene of interest are digested by same restriction enzymes
- gene is inserted and ligated into T-DNA of plasmid
- transformation of plasmid with insert back into bacteria
- bacteria grown with plant cells in culture
- T-DNA inserted into plant chromosome/genome
= plasmid also has selectible marker to know whether its in the plant cell or not (antibiotic)
what are biolistics and how does it work - not method just the idea
‘Biological ballistics’
physical method of introducing DNA into plant cells
shoot microscopic gold partciles coated in DNA at plant tissues
describe the method of ballistics for genetic modifications of plants
- fire gold particles coated in DNA at plant tissue
- place on selective media and grow
= only cells with the inserted DNA will survive
name 2 genetically modified plants in commercial use
Firm tomatoes
Non-browning apples
how are firm tomatoes gentically modified
polygalacturonase degrades pectin in cell wall causing softening
= Ti plasmid inserts antisense (backwards) polygalacturonase gene
= when this is transcribed it binds to the normal ‘sense’ gene forming dsRNA = cannot be translated
tomatoes remain firm
describe how non-browning apples are genetically modified
polyphenol oxidase causes oxidative browning of apples
added siRNA gene complimentary to polyphenol oxidase
= mRNA is bound to and destroyed by RISC complex reducing expression and delaying onset of browning
