Bio Lab PTC Proctored Exam Questions And Well Elaborated Answers.
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Module
PTC.
Institution
PTC.
objective - correct answer characterize each student's ability to detect bitterness using a PTC test strip; assess if response to unsweetened grapefruit juice correlates with PTC test strip results; determine the density of taste bud-containing fungifor...
objective - correct answer characterize each student's ability to detect
bitterness using a PTC test strip; assess if response to unsweetened grapefruit juice correlates with PTC
test strip results; determine the density of taste bud-containing fungiform papillae (visual assay of the
anterior aspect of student's tongue; correlate with PTC test strip and grapefruit juice responses); isolate
DNA (saline mouth wash extraction), PCR amplify and (HaeIII restriction enzyme) digest a short region of
the TAS2R38 gene from each student to determine student genotype; Assess if there is a relationship
between genotype (TAS2R38 alleles) and phenotype (taste bud density, response to PTC strip, grapefruit
juice); examine the relationship between bitterness tasting ability, avoidance of bitter tasting foods and
incidence of cancer
five basic tastes - correct answer sweet
sour
bitter
salty
umami (MSG L-form)
How does taste work? - correct answer 1. taste molecule binds to receptor on
taste cell
2. cell generates a nervous impulse which is interpreted by the brain
*taste sensation is determined by wiring, not by which type of molecule is bound
phenylthiocarbamide (PTC) dust - correct answer Arthur Fox tasted nothing, CR
Noller tasted bitterness
Albert Blakeslee - correct answer inability to taste PTC is a recessive trait in
human populations (tasters 75%, nontasters 25%)
How many genes for bitter taste receptors? - correct answer 30
, gene for PTC taste receptor - correct answer TAS2R38; three SNPs correlate
with bitter tasting ability (five different haplotypes)
haplotype - correct answer a specific combination of SNPs that correlates with
a trait
SNPs in serotonin transporter/receptor genes - correct answer predict adverse
responses to anti-depression drugs (PROZAC/Paxil)
ability to taste PTC - correct answer presence of at least one dominant allele;
Mendelian inheritance
medium tasters - correct answer heterozygous genotype Tt
Kim et all 2003 - correct answer located and sequenced TAS2R38 (PTC gene)
on chromosome 7; codes for one of the 25 bitter taste receptor proteins
PAV (proline-alanine-valine) - correct answer major taster haplotype (T allele)
AVI (alanine-valine-isoleucine) - correct answer major nontaster haplotype (t
allele)
Miller and Reedy - correct answer methylene blue solution to stain the
anterior tongue; variations in number of fungiform papillae and tastebuds in individuals (increase in PTC
tasting increased with density of fungiform papillae)
filiform papillae - correct answer do not contain taste buds; deep blue stain
fungiform papillae - correct answer contain tastebuds; light staining, can be
counted
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