Mr G bio 6 Genome projects and Gene technologies Flashcards
what is a genome?
Complete set of genes in an organism.
what must happen before gene sequencing methods can be used?
Gene sequencing methods only works on fragments of DNA, so to sequence the entire genome of an organism, the DNA must be chopped up first.
Smaller pieces are sequenced and then put back in order to give the sequence of the whole genome.
what is the proteome?
range of proteins an organism can produce
why is sequencing proteomes easier in simple organisms?
Bacteria do not have non-coding DNA.
Easy to determine their proteome from the DNA sequence of their genome.
why is sequencing proteomes in simple organisms useful in medical/scientific research?
identifies protein antigens on the surface of disease causing bacteria and viruses – vaccines.
Also allows scientists to monitor pathogens during an outbreak of a disease – leads to better management of the spread of infection and can help identify antibiotic resistance factors.
why is translating a genome into a proteome difficult in complex organisms?
-contain large sections of non-coding DNA
-contain compex regulatory genes, which determine when the genes that code for particlar proteins are turned on and off
makes it hard to find parts of genome that code for proteins
what were sequencing methods like in the past?
labour- intensive, expensive and could only be done small scale
how have new sequencing techniques developed?
now techniques are automated, more cost effective and can be done on a large scale. scientists can now sequence whole genomes much more quickly
what does recombinant DNA technology involve?
Recombinant DNA technology involves transferring a fragment of DNA from one organism to another.
what is recombinant DNA technology used for?
Because the genetic code is universal, and because transcription and translation mechanisms are universal, the transferred DNA can be used to produce proteins in the cells of the recipient organisms.
Donor and recipient organisms do not have to be the same species.
what is a transgenic organism?
organisms that contain transferred DNA
what is needed before you can transfer a gene from one organism to another?
need to get a DNA fragment containing the gene that you are interested in (target gene)
what are the 3 methods of making DNA fragments?
-Using Reverse Transcriptase
-Using Restriction Endonuclease Enzymes
-Using a Gene Machine
why is it difficult to obtain a DNA fragment containing the target gene?
as most cells only contain 2 copies of each gene. BUT cells that produce the protein coded for by the target gene will contain many mRNA molecules which are complementary to the gene – so mRNA is easier to obtain.
how can you use reverse transcriptase to make a DNA fragements?
-Reverse transcriptase, makes DNA from an RNA template.
-The DNA produced is called complementary DNA (cDNA).
-mRNA must be isolated first, then mixed with free DNA nucleotides and reverse transcriptase, making cDNA.
how are restriction endonuclease enzymes able to make DNA fragments?
-Some sections of DNA have palindromic sequences of nucleotides.
-These sequences consist of antiparallel base pairs (base pairs that read the same in the opposite direction).
when can restriction endonucleases be used?
-If recognition sites are present at either side of the DNA fragment you want, you can use restriction endonucleases to cut the fragment out from the rest of the DNA.
-The DNA sample is incubated with the specific restriction endonucleases, which cuts the DNA fragment out via a hydrolysis reaction.
what happens after the DNA fragment is cut out using restriction endonucleases?
Sometimes the cut leaves sticky ends – small tails of unpaired bases at each end of the fragment.
Sticky ends can be used to bind (anneal) the DNA fragment to another piece of DNA that has complementary sticky ends.
what does a gene machine allow?
fragments of DNA can be synthesized from scratch, without the need for a pre-existing DNA template – made from the knowledge of the primary sequence
Instead, a database contains all the necessary information to produce the DNA fragment.
This means that the DNA sequence does not have to exist naturally – any sequence can be made.
what is the process of using a gene machine?
1.The sequence is designed.
2.The first nucleotide in the sequence is fixed to a support e.g. a bead.
3.Nucleotides are added step by step in the correct order, in a cycle of processes that includes adding protecting groups. Protecting groups make sure that the nucleotides are joined at the right points, to prevent unwanted branching.
4.Short sections of DNA called oligonucleotides, roughly 20 nucleotides long, are produced. Once these are complete, they are broken off from the support and all the protecting groups are removed. The oligonucleotides can then be joined together to make longer DNA fragments.
what are the two different ways of making many copies of a target gene?
In vivo cloning – gene copies are made within a living organism. As the living organism grows and divides, it replicates the DNA making many copies of the gene.
In vitro – gene copies are made outside a living organism using polymerase chain reaction (PCR).
what is a vector?
something that’s used to transfer DNA into a cell – plasmids or bacteriophages.
what is the process of using In vivo cloning to make recombinant DNA?
1.Vector DNA isolated.
2.Vector DNA is cut open using the same restriction endonucleases that was used to isolate the target gene.
Causes sticky ends of the vector and the target gene to be complementary.
3.Vector DNA and DNA fragment are mixed with DNA ligase.
Ligase joins the sticky ends of the DNA fragment and vector DNA – ligation, by complementary base pairing.
4. Vector DNA + DNA fragment = Recombinant DNA
after recombinant DNA is made during in vivo cloning, what is part 2 (transforming cells)?
- recombinant DNA transfers the target gene into the host cells
- host cells that take up the vector containing the target gene are said to be transformed
3.if a plasmid is used, host cells have to be persuaded to take in recombinant plasmid
