forensics

Question 1

DNA profiling to distinguish species

Answer 1

DNA obtained from two known species
PCR to produce fragments of DNA
gel electrophoresis to analyse DNA samples
GE separates fragments of DNA
more differences in bands= different species

Question 2

role of DNA primers

Answer 2

primers have specific base sequence
bind to complimentary bases either end of the DNA to be amplified
provide site for the DNA polymerase to bind

Question 3

changes in a body the first week after death

Answer 3

body temp falls
rigor mortis
autolysis/ break down of cells by enzymes in the body
putrefaction/ discolouration/ bloating

Question 4

gel electrophoresis procedure

Answer 4

restriction enzymes cut DNA into fragments
DNA samples loaded on to agarose gel
electric current passed through gel
DNA goes to anode
distance moved based on size/ mass of fragment
gene probe/markers/ fluorescent dyes added to visualise bands
compare position of bands produced

Question 5

effect of temp on rate of decompostion

Answer 5

increase temp= faster rate of decomp/ decay
increase temp= increased enzyme activity
= increased growth rate of bacteria/ decomposers

Question 6

southern blotting

Answer 6

fragments transferred to nylon/ nitrocellulose membrane
fragment and buffer absorbed and transferred to adjacent membrane
buffer denatures fragments in process
membrane incubated with excess labelled dna probe- complementary to target DNA sequence
hybridisation occurs and excess unbound probe is washed away

Question 7

DNA probe

Answer 7

may be radioactively labelled / fluorescent marker (visualised under UV) -32P
x ray film exposed to dried membrane- film blackening where probe has hybridized to produce double stranded DNA with required fragment