Paper 1 Flashcards
Describe the structure of DNA and how to extract it from plant cells
Firstly crush the fruit in order to break down the cell wall. Then add washing up liquid to break down the cell membrane and causes the cell to release the DNA, also add salt to cause the DNA to group together. Next sieve the mixture to remove any debris. Finally add some ice cold ethanol, since DNA is insoluble in ice cold ethanol it’ll appear as a white precipitate , which you can then fish out with a glass rod. The DNA itself has a double helix structure held together by hydrogen bonds, it also has a sugar, phosphate and base in a nucleotide. The bases are complimentary and the pairs are Adenine with Thymine and Cytosine with Guanine (or Uracil in protein synthesis)
Explain how plants protect themselves from being eaten by pests and against diseases caused by pathogens.
Plants have 3 different types of defence mechanisms. The first being chemical, where the plant often produces insect repellent in the form of toxic chemicals to drive away pests from eating it, this then also stops pathogens from having an easy way into the plant. The second is physical where the plant has things like waxy cuticles so that pests and pathogens can’t get through, also plant cells have cell walls to act as a physical barrier to stop pathogens getting into the cell. The third is mechanical defences, which are actions like the plant closing up so pests can’t get in, and thorns which stop anything trying to get to the stem , which protects the plant from being eaten
Explain how bacteria can be genetically engineered to produce human insulin
1) The DNA for human insulin is cut out with a restriction enzyme. The bacteria’s DNA is then cut out with the same restriction enzyme
2) The sticky ends of both of the separate DNA’s are put together using ligase enzymes
3) the ligase joins together the pieces of DNA to make recombinant DNA
4) the recombinant DNA is then inserted back into the bacteria plasmid DNA
5) the bacteria containing the gene can now be grown in huge numbers as they reproduce, to help make human insulin for people with diabetes
