22: Recombinant DNA technology Flashcards
what are the characteristics of the family with language impairment?
- Simplified speech
- “poor awareness of appropriate sound patterns”
- Poor articulation
- struggled with complex sequences of tongue movements
- genetic
what is the gene related to speech and language disorder
FOXP2 gene on chromosome 7
What can we do to discover the gene?
- clone to determine sequence
- purify protein to investigate properties
- generate transgenic organism
what is a clone? What is a common cloning bacteria?
copy of the original, Escherichia coli
What are the steps to express FOXP2 in E.coli?
- determine which tissues express FOXP2 (northern blot)
- isolate mRNA
- synthesize cDNA
- PCR FOXP2 from cDNA
- Gel purify FOXP2 PCR product (gel electrophoresis)
- restriction-cut FOXP2 + restriction cut plasmid ligated to recombinant plasmid
- transform recombinant plasmid to E. coli
- verify clones (restriction mapping, DNA sequencing)
- purify FOXP2 from E.coli
What are the types of blotting?
Northern: detect RNA using DNA
Western: detect protein using antibodies
Southern: detect DNA using DNA
What are the steps of northern blotting?
- isolate RNA
- separate RNA by gel electrophoresis
- transfer RNA to membrane
- probe membrane for FOXP2
What are the mechanics of DNA gel electrophoresis?
RNA loaded on to cathode (-) side of agarose gel and it runs to anode (+) side
smaller size = runs faster
How is RNA transferred to a membrane?
stack (gel-nitrocellulose paper-stack of paper towels)
liquid soaks through to paper towel taking the RNA with it, but nucleic acid is stoped by biding tightly to nitrocellulose paper
How is the membrane probed for FOXP2?
synthetic oligonucleotide (part of FOXP2 sequence) is incubated with membrane
wash away unbound probe
radiolabel oligo (probe) to detect bound probe on the membrane
probe is complementary to the FOXP2 gene and is detectable to see which cells express this gene (brain, lung, liver, kidney)
What is complementary DNA (cDNA)?
DNA copy of mRNA that is needed for cloning
How is cDNA formed?
- total mRNA prep
- add poly(T) DNA primer to 5’ new end
- use reverse transcriptase to many cDNA
- RNase H degrades mRNA template and E.coli DNA poly and ligase add and ligate new nucleotides where the mRNA template used to be
transcription can begin/end anywhere on mRNA = mixture of strands - result: mixture of cDNA from all mRNAs in tissue
What is PCR?
polymerase chain rxn
rapid amplification of small DNA amounts
What is necessary for PCR?
template sequence to anneal primers
What are the steps of PCR?
- strands separated at 95ºC strand contains target sequence + excess
- anneal primers 50º-60º to target sequence
- extend primers 72ºC using dNTPs and thermostable DNA polymerase
repeat many times, at 3rd cycle, the exact target FOXP2 cDNA region appears and is amplified and can be purified from the other cDNAs present with gel electrophoresis