1. What characteristic of the genetic code means that scientists are able to use recombinant DNA technology to transfer genes from one organism to another ?
Answer
The genetic code is universal.
2. Describe three ways in which genes are obtained for recombinant DNA technology.
Answer
Using mRNA and reverse transcriptase to make cDNA. Using restriction enzymes to cut fragments containing a gene. Using the "gene machine" to create the desired gene.
3. Describe the difference between in vitro and in vivo gene cloning.
Answer
In vitro is where the Polymerase Chain Reaction is carried out, where DNA fragments are amplified in a thermocycler, where temperature changes enable DNA to be copied exponentially. In vivo is where a cell or organism is transformed by inserting a gene to amplify the DNA fragments.
4. Describe the role of DNA ligase in in vivo gene cloning.
Answer
DNA ligase is used to anneal the DNA fragment to the host cell's DNA by allowing phosphodiester bonds to form on the sugar phosphate backbone.
5. Explain why marker genes are used in in vivo gene cloning.
Answer
Marker genes are used to identify which cells have been transformed as the process is not very successful.
6. What is a DNA probe ?
Answer
A single stranded fragment of DNA which is radioactively or fluorescently labelled.
7. What property of DNA allows it to be separated using gel electrophoresis ?
Answer
It is negatively charged, so will migrate towards the positive electrode at the other end of the gel.
8. What are VNTRs and why are they useful in genetic fingerprinting ?
Answer
There are variable number tandem repeats. The lengths of these repeats are unique to a person. So they can be used to identify genetic relationships as well as in forensic science.
9. How can DNA probes be used in genetic screening ?
Answer
DNA probes can be used in genetic screening to identify whether a person carries a particular allele, which helps detect heritable conditions. Genetic counsellors can then use this information to advise patients. Probes can also be used in embryo testing: DNA is extracted, amplified using PCR, separated by gel electrophoresis, and then analyzed with a probe to identify embryos that do not carry the defective allele.
10. Why would the use of genetic fingerprinting be useful in animal breeding programmes ?
Answer
Able to see how closely related animals of the same species are and then decide which animals to breed based on them being as genetically different as possible. This can prevent inbreeding.
11. Scientists are using genetic fingerprinting to identify which shark fins have been obtained from endangered species. Scientists developed genetic markers that enabled them to identify 26 distinct shark species, based on DNA fingerprinting. Each individual shark has a unique DNA fingerprint. Suggest how scientists are able to use this technique to identify what species a shark fin is from.
Answer
Each species has VNTRs that are unique to that species. These unique VNTRs can be sequenced, and probes are designed for these specific markers. The probes attach to VNTRs with complementary sequences, thereby indicating which species is present.