Topic 6 Flashcards
what are the 5 ways used in determining the time of death of a body?
degree of muscle contraction body temperature extent of decomposition forensic entomology stages of succession
describe the stage of succession in the dead body?
decomposed by bacteria. make conditions favourable for flies and larvae.these feed on the dead body leaving dead tissue for Beatles. as body dries, conditions less favourable for flys, Beatles remain decomposing dead tissue leaving skeleton. used as a source of energy allowing bacteria and fungi to grow. bacteria and fungi secrete enzymes making breaking the dead body down to smaller organic molecules. affected if its above ground or in water.
what is forensic entomology?
helps to determine the time of death by looking at the insects in body
effects of temperature on TOD
the body cools at a rate of 1.5 degrees to 2 degrees per hour. the body is 37 degrees will cool because metabolic processes will stop. air temperature body weight and clothing will affect the temperature
muscle contraction
respiration stops so muscles are deprived of oxygen. muscles respire anaerobically so the build-up of lactic acid meaning ph lowers and so the bonds between the actin and myosin become fixed. smaller muscles stiffen first. if the temperature is hight then stiffness increases as chemical reactions happen faster.
rate of decomposition?
decompose dead material into smaller molecules respiring them and releasing co2 and ch4 back into the atmosphere.
how can one mRNA strand give rise to different proteins?
mRNA splicing in the post transcriptional phase where introns are removed but exons remain. arrangement of exons in the strand will give rise to different proteins.
describe stages of PCR
DNA into the thermal cycler with DNA primers DNA polymerase (usually tac polymerase as it can handle high temperatures), DNA primers with fluorescent markers( complementary to one end of DNA fragments), nucleotides.
95 degrees denaturation occurs
DNA strand separated
reduces down to 55 degrees and primers with florescent markers will start, annealing occurs
70 degrees DNA polymerase attaches and nucleotides are added extending the DNA from the primer. two new DNA strands are produced with 4 fragments
millions of this str are produced and can be separated by gel electrophoresis
why is the agarose gel smeared with alkali?
to separate DNA strands
why is endonuclease added to DNA?
it is a restriction enzyme which identifies restriction sites and cuts down DNA into fragments.
why is DNA negative charged?
the phosphate group is negatively charged so DNA will voe to positive end once electrode turned on and there is a power supply
why is nylon membrane used?
hard to observe DNA fragments so nylon membrane used for souther blotting. DNA fragments soak up the nylon membrane and so southern blotting allows soaked up. then hybridisation as the dye is added to the nylon membrane. then out under UV light to view the fragments properly
