8.3 + 8.4 Flashcards
what are genome projects used for
determining the complete sequence of bases that make up the DNA of an organism
how to gene sequencing work
by cutting the DNA molecule into fragments which are sequenced and then they are put back into correct order to give the sequence of the whole genome
what can sequencing be used for
comparing genomes with species highlighting disease risk, improve understanding of inherited disorders and track early migration patterns with evolutionary relationships between species
what is the proteome
the sequence of proteins coded for by the DNA base sequence of the genome
what can finding the genome of simple organisms help with
intensifying antigens of viruses monitoring mutations as the pathogen evolves allowing us to produce vaccines faster controlling the spread of infection
why is it hard to determine the human proteome
as over 98% are introns (non-coding) so hard to determine which are exons
what are the three methods of making DNA fragments
- using reverse transcriptase to make cDNA
- genes can be found and ‘cut out’ using restriction enzymes
- Using a gene machine to build fragments
what can reverse transcriptase do
an enzyme that can convert RNA back into DNA
what does reverse transcriptase do in making DNA fragments
is is added using free DNA nucleotides to make DNA from the mRNA template which is called cDNA as it is complementary DNA matching the RNA
what do restriction endonuclease do
enzymes that can recognise and hydrolyse hydrogen bonds at specific sequences of DNA
what do restriction endonuclease do in making DNA fragments
they cut at a specific recognition sequence in the DNA which is complementary to their active site
what do restriction enzymes do
form sticky ends (pieces of DNA that have exposed nucleotides on a single strand at each end) allowing different fragments to be joined together
4 steps of using a gene machine to build DNA fragments
- the sequence is designed on a computer
- the first nucleotide in the sequence is attached to a physical support
- nucleotides are added step by step in the right order and joined in the correct place to prevent branching
- short sections of DNA called oligonucleotides are produced (20 nucleotides long). once these are complete they are broken off from the support and can be joined together to make longer fragments
what is the difference between in vivo and in vitro
vivo takes place in living organsims
vitro is not in living organisms translating to in glass
first step of in vivo
- desired gene is isolated using restriction endonuclease enzymess
second step of in vivo
promoter genes and terminator regions are added to the gene to make sure the gene can be correctly transcribed once in the host
- promotor tells RNA polymerase where to start and terminator tel RNA polymerase where to stop
third step of in vivo
the gene is inserted into a vector
cut the plasmid and the gene with same restriction endonuclease enzyme to leave ‘sticky ends’ allowing the target gene to fuse with the plasmid
ligase enzymes can join these two DNA fragments together by catalysing condensation reactions that join the sugar groups and the phosphate groups to the DNA backbone
when DNA fragments and plasmids are mixed not all plasmids will take up the gene correctly so DNA fragments that dont get inserted can also join its own sticky ends to create a loop
fourth step of in vivo
the recombinant plasmid is now transferred to host cells
a solution such as sodium chloride can be used to make cell walls more permeable, heat shock can be used or electroporation to make holes in membrane which DNA can pass through
step five in in vivo
the host cells are allowed to multiply and those that have successfully taken up the gene are identified using a marker gene
marker genes are inserted into vectors at the same time the gene is, these can code for antibiotics resistance and only transformed bacteria will survive.
as the genetic code is universal bacteria can transcribe DNA and translate the mRNA to produce the protein
what is PCR
the artificial replication of short sequences of DNA using artificial DNA primers to amplify a specific strand of DNA
what are the 4 steps of PCR (in vitro)
- the mixture is heated to around 95C to break the hydrogen bond between the complementary nucleotide base pairs and separate the double-stranded DNA into two single strands
- the mixture is cooled to around 55-60C so that primers can bind forming hydrogen bonds to one end of each single strand of DNA which identifies where tax polymerase should bind
- the temperature is raised to around 72C which is the optimum temperature for Taq DNA polymerase catalysing the addition of DNA nucleotides by complimentary base pairing to create two complete double strands of DNA
- repeat