lecture 21, plant DNA part 2 Flashcards
what are the advantages of “selfing”?
- progeny 100% related to parent, but can also pollinate others
- reproduce when pollinators are rare
- fast spread through new habitat
what are the most common transitions in flowering plant evolution?
evolution from outcrossing to predominant self-fertilization
what is a diploid?
one copy from maternal and one from paternal
what percentage of all known plant genera are polyploid?
50%
define autopolyploidy
doubling of chromosome number within individual organism
define alloploidy
chromosomes from closely related species
how does autopolyploidy occur?
nondisjunction in meiosis followed by fertilization
how does allopolyploidy occur?
autopolyploidy occurring followed by meiosis
animal genomes are very sensitive to …
mutations
what is paleo-polyploidy?
whole genome duplication events, followed by gene diversification and loss
what kind of error do gametes have?
meiotic error
greater genetic material leads to …
robustness
more gene products –> more tissue
what does ancient genome duplication eventually lead to?
loss of genes, re-diploidization
plant genomes are more …. than animal genomes
flexible, more resilient to chance mutations sub- and neo-functionalization of duplicated genes. grow despite genetic modification
what are the main systems of genetic transformation?
- agrobacterium tumefaciens
- CRISPR/Cas9
DNA recombination works by …
DNA from carrier recombines with another organism’s DNA. can be a plasmid or virus
using recombinant DNA technology ….
one can insert transgenes and novel genotypes
how does gene cloning by recombination work?
- restriction enzymes cut donor/vector DNA
- ligated
- bacterial host is transformed with recombinant plasmid
- bacterial cell proliferates
- culture or plate-full of bacteria growing
BUT not all cells will contain recombinant DNA
what is a reporter gene?
a gene that can be easily assayed
what is a chimeric gene?
genes produced from the fusion of two or more parent genes
traits of agrobacterium tumefaciens:
- soil-dwelling bacterium
- infects wide range of angiosperms; via sounds
- crown-gall tumours
- tumor-inducing (Ti) plasmid
- contains transfer DNA
Ti plasmid:
- 100 genes
- T-DNA region: 20,000 bp
- Gene O: amino acid derivative
- onc region: hormone biosynthesis (grow and divide uncontrollably)
- vir region: transfer process
what happens in transgenic plants?
T-DNA genes are replaced by genes of interest. genes are inserted into plant’s genome
why is A. tumefaciens transformation a major limitation?
no control over location of DNA insertion in host genome and can knock out a major function, e.g. photosynthesis or a low expression region
what is CRISPR-Cas9?
a prokaryotic immune system against viruses/pathogens, that uses DNA sequences from past pathogens to recognize new invaders and cleave them
how is CRISPR/Cas9 applied to engineering?
- Cas9 nuclease complexed with synthetic gDNA
- cut at specific location
- edit and/or add new DNA
- using host repair system
examples of benefits to genetic engineering in plants:
- add new traits; salt / drought-tolerance
- new flavors
- save native species; resistance against rapidly-spreading viruses
