w4 saliva Flashcards
describe the difference between amylose and amylopectin
amylose is a straight chain polymer of glucose
amylopectin is a branched chain polymer of glucose
what two types of amylase are there?
salivary amylase
pancreatic amylase
what body fluids can be found to be positive in the phadebas paper test
saliva
urine
blood
semen
summarise the validation of the phadebas press test by Wornes et al
- sensitive to alpha amylase activity
- less specific for saliva
- temp has no effect on sensitivity at 37 degrees
- increased incidence of cross reactivity with other body fluids at 37 degrees
- blood/urine/vaginal secretions can inhibit the detection of alpha-amylase
- weak predictor for time taken to observe positive result
summarise the effect of temperature on phadebas press test by woodford et al
optimal in vitro temp for alpha amylase is 37degrees
no statistical significance in intensity of phadebas reactions at room temp and 37degrees
max sensitivity and performance can be achieved at room temp
what is the phadebas tube test
utilises the same starch molecules but in tablet form
saliva stain extracted into a tube and tablet is added to solution
presence of alpha amylase will cause the blue dye molecules to be released into solution turning the solution blue for a +ve result
deeper the blue = estimate qualitative estimate of amylase activity
more sensitive than the press test
what instrument would you use to produce semi quantitative data for the phadebas tube test
spectrophotometer
–> light passes through samples and into photoelectric detector to measure amount of light absorbed by sample
deeper the blue = more light absorbed
high absorbance = high amylase activity
prevalence transfer and persistance in vehicles
presence may be due to direct or indirect transfer
salivary amylase was detected in 53% of all samples collected
positive samples yielded more dna than negative samples
steering wheel has greatest number of saliva positive samples
drivers dna profile was detected in72% of total samples taken
saliva can persist for at least ten days
persistence of saliva after showering Williams et al
saliva can persists on skin after showing for 8 mins
FMEs should sample from the skin even is victim has showered or was unconscious
enough saliva was present after shower to provide Y-STR profile
conventional STR analysis was unsuitable as female obscured trace of male dna
persistence and recovery of saliva Kenna et al
minitape method more effective than swabbing
salivary dna will persist on skin up to 96 hr
dried salivary dna will transfer from skin to material in contact with skin
transfer of saliva - oral intercourse
saliva can be transferred to external vaginal area of females
support for oral intercourse vs secondary transfer
oral intercourse vs secondary transfer
What is the probability of finding saliva and matching DNA of person A from the underwear of person B, if person A performed oral sex on person B?
What is the probability of finding saliva and matching DNA of person A from underwear of person B, if person A did not perform oral sex on person B?
finding from 69 pairs of male underwear
44% gave a positive result for amylase using press test
stains located on I/S front and around waistband
87% were false positives for salivary amylase.
–> most likely to be attributed to other body fluids contain pancreatic amylase
female alleges she was forced to perform oral sex
male suspect arrested 36 hours later and denied it happened. his underwear was recovered
Hp = complainant performed oral sex upon the defendant
Hd = the complainant did not perform oral sex upon the defendant
