Biology Quiz Question Pool on PCR and Taste Receptors

Quiz Question Pool 8 2026 Notes

This document outlines a quiz question pool focusing on the concepts related to the Polymerase Chain Reaction (PCR) and sensory perception, particularly taste. The questions are designed to probe various aspects of genetics, biochemistry, and molecular biology.

What is a SNP?
- Definition:
- Acronym: SNP stands for Single Nucleotide Polymorphism.
- Explanation: A SNP is a variation in a single base pair in the DNA sequence among individuals. SNPs can occur in coding or non-coding regions of the genome and potentially affect how humans respond to diseases, environmental factors, and medications.

What 5 tastes can your taste buds perceive?
- Tastes:
1. Sweet
2. Sour
3. Salty
4. Bitter
5. Umami (savory)

How many different taste receptors does a taste receptor cell that tastes sweet substances have?
- Specifics:
- There are primarily two receptors associated with sweet taste perception: T1R2 and T1R3.
- A taste receptor cell that detects sweet substances can express one or both of these receptors.

How many different taste receptors could a taste receptor cell that tastes bitter substances have?
- Details:
- Bitter taste receptors belong to the T2R family. There are approximately 25 different T2R receptors in humans, allowing for the detection of a wide variety of bitter compounds.

a. Which gene encodes the receptor primarily responsible for tasting PTC?
- Gene:
- The TAS2R38 gene encodes the receptor responsible for tasting phenylthiocarbamide (PTC).
- b. How many common SNPs are in this gene?
- SNPs:
- There are three common SNPs in the TAS2R38 gene.
- c. What combination of amino acids encoded by this gene is generally found in tasters?
- Amino Acids (tasters):
- Tasters generally have the amino acid combination Proline-Alanine-Valine (PAV).
- d. What combination of amino acids encoded by this gene is generally found in non-tasters?
- Amino Acids (non-tasters):
- Non-tasters typically have the amino acid combination Alanine-Valine-Isoleucine (AVI).

a. What percentage of people are neither PAV nor AVI?
- Percentage:
- About 25% of individuals fall into the category of neither PAV nor AVI.
- b. Are these people liable to taste PTC?
- Tasting Ability:
- Individuals who do not have either the PAV or AVI combinations may be unable to taste PTC at all, indicating a non-taster phenotype.

What enzyme is used in PCR? What is its preferred operating temperature?
- Enzyme:
- Taq polymerase (derived from the bacterium Thermus aquaticus) is the enzyme used in PCR.
- Temperature:
- Its preferred operating temperature is approximately 75-80 °C for optimal activity during DNA synthesis.

What substitutes for RNA polymerase in PCR? Explain what function is carried out.
- Substitute:
- Taq polymerase acts as a substitute for RNA polymerase.
- Function:
- It synthesizes new strands of DNA complementary to the template strand during the extension phase of the PCR process.

What substitutes for DNA helicase in PCR? Explain what function is carried out.
- Substitute:
- The heating of the PCR reaction mixture substitutes for DNA helicase.
- Function:
- This heating denatures the DNA into two single strands by breaking the hydrogen bonds between the nucleotide base pairs.

What are the three steps of PCR? How many times are they carried out?
- Steps:
1. Denaturation: Heating the reaction to separate the DNA strands.
2. Annealing: Cooling the reaction to allow primers to attach to the single-stranded DNA.
3. Extension: Increasing the temperature for Taq polymerase to synthesize new DNA strands.
- Cycles:
- These steps are typically repeated 20-40 times, doubling the amount of DNA with each cycle.

What determines the length of a PCR product?
- Determinants:
- The PCR product length is determined by the distance between the two primers used in the reaction and the sequences between them.

a. Draw a diagram of what occurs in PCR during the annealing step of the FIRST cycle.
- Diagram Description:
- [Insert diagram showing primers binding to template DNA strands in the first cycle]
b. Draw a diagram of what occurs in the annealing step in the LAST cycle in the vast majority of cases.
- Diagram Description:
- [Insert diagram showing multiple copies of DNA strands with primers closely bound at complimentary sites in the last cycle]

a. If your PCR product contains a Hae III site, do you encode proline or alanine at position 49?
- Answer:
- You would encode proline at position 49.
- b. Are you liable to be a taster for PTC?
- Answer:
- Yes, if you encode proline at position 49, you are more likely to be a taster for PTC.
- c. Is this Hae III site actually contained in your DNA?
- Answer:
- Yes, the Hae III site would be present in your DNA if you carry the taster allele.

From what kind of tissue did you amplify your DNA? What was the alternative?
- Tissue Source:
- DNA was amplified from buccal (cheek) cells.
- Alternative:
- The alternative tissue source could be blood or saliva samples.

What purpose does Proteinase K serve in preparing your genomic DNA?
- Function:
- Proteinase K is a proteolytic enzyme used to digest proteins that could interfere with the extraction and analysis of genomic DNA. It helps in breaking down contaminants and improving DNA yield.