DNA technology 2 Flashcards
Why is PCR used in genetic fingerprinting
- Only small amounts of DNA extracted
- PCR increases the amount
- So enough DNA is available for comparisons
Describe genetic fingerprinting
- DNA extracted from sample
- DNA cut into fragments by RE
- DNA fragments separated using electrophoresis
- This is according to length/mass
- description e.g put mixture in wells on gel and apply electric current
- immerse gel in alkaline solution so the 2 strands separate
- Cover with nylon to absorb DNA
- Radioactive probe is added
- Autoradiography is used to identify probes
Why is measuring the no of base pairs a suitable way to measure DNA length
- DNA made up of base pairs (2 polypeptides)
- Each base pair is the same length as they occupy the same distance along backbone
Differences between PCR and DNA replication
- PCR uses heat to separate strands wheras DNA rep uses DNA helicase
- PCR replicates DNA pieces as DNA is cut whereas DNA rep replicates the whole thing
What is a probe and how is it used?
- Short, single strand of DNA;
- Has base sequence that is complementary to part of target gene;
- Will H-bond to strand
- Fluorescent labelling present
- So can tell if someone has a specific gene as the probe will bind to it
Ways in which the information obtained from gene probes is helpful to a doctor who is counselling someone with a family history of cancer.
- Identify carriers of cancer gene
- Identify which cancer gene present;
- Identify most effective treatment;
Assuming the base sequence of a specific gene is known. how could we detect a mutation of this gene in a sample of cells
- extract DNA;
- remove specific section using restriction endonuclease
- Use sanger sequencing
- compare with normal sequence for gene;
Suggest how the information acquired through research on biological markers could be used to reduce deaths from cancer.
- can spot individual at high risk so allows earlier detection of tumours;
- earlier surgery or drug treatment which increases chances of survival
Explain why the core sequences will vary between individuals
- RE cuts at specific base sequences
- RE isolates the introns
- Sequence of repeated bases will differ
- Number of repetition determines DNA fragment length
How can adding DNA fragments size be used to show incomplete digestion by restriction enzymes
- Large pieces of DNA present;
- Fragments add up to more than total length of original DNA / plasmid plus inserted DNA;
- Because this would add undigested to total (original) length;
Methods to find the base sequence of a gene
- Restriction mapping
- Then Sanger sequencing
Why should we use the same RE
- Cut DNA at same base sequence (recognition sequence)
- So get fragments with required gene
When trying to locate which chromosome has a specific gene, why use probes on cells undergoing mitosis
- Cells in mitosis so chromosomes visible;
- So can see which chromosome DNA probe attached to;
Benefits of using a marker e.g glow over genes that confer antibiotic resistance
- Antibiotic resistance not transferred;
- Easier/quicker to identify modified bacteria
What is a marker gene
- Gene coding for easily identifiable product
- Allows scientists to see if (X) contain transferred gene
