DNA Technology Flashcards
Describe how reverse transcriptase is used to isolate a gene?
Produce MRNA from DNA.
CDNA is produced complementary to that of mRNA, it is shorter as it does not contain introns.
DNA polymerase adds free nucleotides
How do restriction endonucleases isolate a gene?
The enzymes cut a double stranded segment of a DNA at a recognition sequence
The cut is in a staggered fashion forming ‘sticky ends’
What is the benefit of sticky ends?
If the same restriction enzyme is used DNA from one organism can be combined with that of another
Name the type of enzyme used to cut open the plasmid
Restriction endonuclease
Name the type of enzyme used to insert the gene into the plasmid
DNA Ligase
Explain why some of the plants in stage 5 contained the desired gene in all of their cells
and others did not
- (DNA of desired gene) copied/replicated
with host DNA/inside nucleus; - Passed on by mitosis/plant grows by
mitosis; - Produces genetically identical cells/clones
Why can plants synthesis insect protein?
Genetic code is universal
Can be transcribed and then translated
How can a mutation not lead to a change in the amino acid sequence?
Genetic code is degenerate
Mutation in introns
A mutation of a tumour suppressor gene can result in the formation of a tumour. Explain how.
Tumour suppressor gene inactivated
Leading to uncontrolled cell division
Some cancer cells have a receptor protein in their cell-surface membrane that binds to a hormone called growth factor. This stimulates the cancer cells to divide.
Scientists have produced a monoclonal antibody that stops this stimulation.
Antibody has specific tertiary structure
Complementary to receptor protein
Prevents GF binding to receptor
Explain why the pieces of human DNA would be able to join to the cut DNA of the plasmids.
They have sticky ends
What is a vector ?
A carrier of DNA into another organism
Molecular biologists often use plasmids which contain antibiotic resistance genes. Explain the reason for this
It acts as a marker gene
It allows detection of cells containing plasmid
What is recombinant DNA technology?
Involves the transfer of fragments of DNA from one organism to another
Describe 3 methods in which fragments of DNA can be produced
conversion of mRNA to complementary DNA (cDNA), using reverse transcriptase
using restriction enzymes to cut a fragment containing the desired gene from DNA
creating the gene in a ‘gene machine’.
How can a gene be isolated by reverse transcriptase?
Produces mRNA from DNA resulting in cDNA
DNA polymerase adds nucleotides
Why is CDNA shorter than original gene?
It does not contain introns
Why is it easier to obtain the gene from mRNA rather than directly from DNA removed from human cells
MRNA is present in large amounts in cell making protein
What does ligase do?
Joins two pieces of DNA
Molecular biologists often use plasmids which contain antibiotic resistance genes, why?
They act as a maker gene which allows detection of cells containing the plasmid
Why would you insert plasmids into the eggs of silkworms rather than into the silkworms?
So that the gene gets into all of the cells
Particularly those that produce the silk
suggest how the binding of interferon gamma to its
receptor protein leads to the production of phosphorylated STAT1
Changes shape of the tertiary structure
This activates an enzyme
requires use of ATP
What is the first step of the polymerase chain reaction?
High temperature breaks H bonds separating double helix
What happens in the annealing stage of the polymerase chain reaction?
Primers bind to strand of DNA. Happens at a lower temperature
Primers are designed to recognise foreign DNA
Why is TAQ polymerase used in the polymerase chain reaction and what does it do?
It can work at high temperatures and does not denature
It forms phosphodiester bonds forming back bone of new DNA strand
What is the polymerase chain reaction used for?
To amplify fragments of DNA
