8B Genome Projects and Making DNA Fragments Flashcards
Define genome
the entire set of DNA
What do gene sequencing methods only work on
DNA fragments
What allowed us to sequence the genomes of organisms
Improvements in technology
What is the Human Genome Project
A project completed in 2003, which mapped the entire sequence of the human genome for the first time
Define proteome
All the proteins that an organism is able to produce
Why is it easier to determine the proteome of simple organisms
it is easier to determine the proteome from the genome of simple organisms as they don’t have much non coding DNA
What can the proteome of organisms be used for
in medical research and development
Why is it harder to translate the genome of complex organisms
More complex organisms have large sections of non coding DNA and they contain complex regulatory proteins which determine when the genes that code for particular proteins should be switched on and off, this makes it more difficult because it’s hard to find the bits that code for proteins among the non coding and regulatory DNA
What were gene sequencing projects like in the past compared to now
Labour intensive, expensive and can only be done on a small scale, now they are automated, more cost effective and can be done on a large scale
Describe recombinant DNA technology
This involves transferring a DNA fragment from one organism to another
How are DNA fragments made by using reverse transcriptase
The mRNA molecules can be used as templates to make lots of DNA
Reverse transcriptase make complementary DNA from an RNA template
Eg pancreatic cells produce the protein insulin . They have loads of mRNA molecules complementary to the insulin gene but only two copies of the gene itself. So reverse transcriptase can be used to make cDNA from the insulin mRNA
How are DNA fragments made by using restriction endonuclease enzymes
Some sections of DNA have palindromic sequences of nucleotides these consist of antiparallel base pairs
Restriction endonuclease enzymes are enzymes that recognise specific palindromic sequences and cut the DNA at these places
Different Restriction endonuclease enzymes cut at different specific recognition sequences because the shape of the recognition sequence is complementary to the enzymes active site
If recognition sequences are present at either side of the DNA fragment you want you can use restriction endonucleases to separate it from the rest of the DNA
The DNA is incubated with the specific restriction endonuclease which cuts the DNA fragment out of the DNA via a hydrolysis reaction
Sometimes this leaves sticky ends - small tails of unpaired bases at each end of the fragment that can be used to bind the DNA fragment to another piece of DNA that has sticky ends with complementary sequences
How are DNA fragments made by using a gene machine
The sequence that is required is designed
The first nucleotide in the sequence is fixed to some sort of support
Nucleotides are added step by step in the correct order in a cycle of processes that include adding protecting groups which make sure that nucleotides are joined at the right points to prevent unwanted branching
Short sections of DNA called oligonucleotides roughly 20 nucleotides long are produced and then they are broken off the support and the protecting groups are removed
