Manipulating genomes Flashcards
what are the techniques used to study genes
- polymerase chain reaction
- gel electrophoresis
- cutting out DNA fragments using restriction enzymes
how can copies of DNA fragments be made using the polymerase chain reaction
- reaction mixture contains DNA sample, free nucleotides, primers and DNA polymerase
- mixture heated to 95 degrees to break hydrogen bonds between DNA strands
- DNA polymerase doesn’t denature
- mixture cooled primers can bind
- mixture heated again for DNA polymerase to work
- DNA polymerase lines up free DNA nucleotides along template strand
- 2 new copies of DNA are formed and 1 cycle of PCR is complete
- cycle starts again, all 4 strands are used
- each PCR cycle doubles the amount of DNA
how can gel electrophoresis separate DNA fragments by size
-gel tray placed into a gel box
- gel tray with wells is closest to negative electrode on the gel box
- add buffer solution and surface of the gel is covered
- add same volume of loading dye to each set volume of fragmented DNA - samples sink
- record which DNA sample you have added to each well
- put lid on the gel box and connect leads from gel box to power supply
- turn on power supply and set to voltage
- DNA fragments are negatively charged and moved to positive electrode
- DNA fragments separate according to size
how are restriction enzymes used to cut out DNA fragments
- sections of DNA have palindromic sequences of nucleotides - antiparallel base pairs
- restriction enzymes recognise these
- cut DNA at these places
- different restriction enzymes cut at different specific recognition sequences as the shape of the recognition sequence is complementary to an enzymes active site
how can electrophoresis produce DNA profiles
- organisms genome consists of repetitive non-coding base sequences - don’t code for proteins
- number of time the non-repetitive sequence is repeated differs from each person
- analysed using electrophoresis - creates DNA profile
how can DNA profiling be used in forensic science
- DNA isolated from all collected sample from crime scene and suspects
- PCR amplifies multiple areas containing different sequences
- primers bind to either side of repeats - whole repeat is amplified
- PCR products run on electrophoresis gel and DNA profiles compared to see if there is a match
- if the sample matches it links a person to a crime scene
how can DNA profiling be used in medical diagnosis
- identify unique pattern of alleles
- analyse risk of genetic disorders
what is genetic engineering
- altering of DNA - transformed organisms
- organisms have recombinant DNA
- extracting a gene from one organism and inserting into another
what is the process of genetic engineering
- DNA fragment containing the gene is isolated using restriction enzymes
- DNA fragment inserted into vector DNA
- vector DNA cut open using restriction enzyme
- sticky ends of the vector are complementary to sticky ends on DNA
- vector DNA and DNA fragment mixed with DNA ligase - joins up sugar-phosphate backbone
- recombinant DNA formed
- vector with Recombinant DNA transfers gene into bacteria cells
what is gene therapy
- altering alleles inside cells to cure genetic disorders
- caused by 2 recessive = add dominant
- allele inserted into the cell using vectors
what is somatic therapy
- altering alleles in body cells
- for cystic fibrosis targets epithelial cells lining the lungs
- doesn’t affect sex cells - offspring could have disease
what is germ line therapy
- altering alleles in sex cells
- offspring won’t inherit the diseases
- illegal in humans
what are the positive ethical issues surrounding gene therapy
- prolong the lives of people with genetic disorders = better quality of life
- decrease the number of people who inherit a genetic disorder
what are the negative ethical issues/ disadvantages surrounding gene therapy
- expensive
- potential to do more harm than good
- effects may be short lived
- undergo multiple treatments
- allele inserted into the wrong place or overexpressed
how can DNA be sequences by the Chain-Termination method
- DNA primer, DNA polymerase, single stranded DNA, free nucleotides and fluorescently labelled modified nucleotide in 4 tubes
- tubes undergo PCR - produces many DNA strands - strands different lengths
- DNA fragments in each tube are separated by electrophoresis
- complementary base sequence can be read
- smallest nucleotide at the bottom of the gel - read from bottom to top
