Lab Course on Bitter Taste Perception

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Questions and Answers

What is the role of the Fnu4H1 restriction enzyme in the analysis of the TAS2R38 gene?

It digests the TAS2R38 gene at a specific recognition site. (correct)

It synthesizes primers used in PCR.

It amplifies the TAS2R38 gene by adding nucleotides.

It modifies the pH of the digestion buffer.

Which nucleotide sequence variation is assessed at position 785 of the TAS2R38 gene?

DNA methylation changes.

Single nucleotide polymorphisms (SNPs). (correct)

A single nucleotide insertion.

A single nucleotide deletion.

What is the primary function of PCR in the amplification of the TAS2R38 gene?

To separate alleles of the TAS2R38 gene.

To increase the number of copies of DNA fragments. (correct)

To cut DNA fragments into smaller pieces.

To sequence the entire TAS2R38 gene.

What is the expected length of the PCR product for the TAS2R38 gene?

312 bp. Signup and view all the answers

What type of genetic variation does the TAS2R38 gene primarily influence?

Bitter taste perception. Signup and view all the answers

What type of receptor does TAS2R38 encode to mediate the perception of bitterness?

G protein-coupled receptor Signup and view all the answers

Which of the following genotype combinations represents a weak taster phenotype?

Tt - weak taster Signup and view all the answers

During the Polymerase Chain Reaction (PCR), which component is primarily amplified?

Gene of interest Signup and view all the answers

Which of the following processes is NOT part of the bitterness detection pathway mediated by TAS2R38?

Direct ion channel opening Signup and view all the answers

How many times is the Polymerase Chain Reaction (PCR) typically repeated to achieve ample amplification?

What is the significance of the 312 bp fragment in the context of genetic variation in taste perception?

It signifies the presence of homozygous taster alleles. Signup and view all the answers

Which method is primarily used to analyze the gene for its SNPs in the laboratory setting?

Polymerase Chain Reaction (PCR) Signup and view all the answers

In the context of restriction enzyme digestion, what does the presence of 206 bp and 106 bp fragments suggest?

The DNA sample contains heterozygous alleles. Signup and view all the answers

Which statement best describes the function of the bitter taste receptor in relation to genetic variation?

It plays a crucial role in detecting harmful substances. Signup and view all the answers

What is a critical step in preparing a lab report when analyzing the genotype associated with PTC tasting?

Summarizing data with appropriate figures and tables. Signup and view all the answers

Study Notes

Lecture Aims

The lecture aims to explain how labs will be run in FTIB
It aims to explain how bitter chemicals in food are tasted.
It aims to explain the SNPs involved in the bitter taste perception gene (TAS2R38).
It aims to explain the methods used to determine the genotype of bitter taste perception.

Lab Help and Support

Peers in the labs are available for help.
The Moodle forum is a resource for questions.
R help sessions are offered.
Jenny August (SLD Maths Adviser) provides support.
Face-to-face labs are essential.

Health and Safety in the Lab

Lab coats, no shorts or sandals, and tied-back hair are required.
Safety glasses are mandatory.
Wash hands before and after lab work.
No eating or drinking in the lab.
Coats/bags must be placed under benches.
Maintain a clean bench area.

Overall Aim of the Lab Course

Characterize phenotypic and genotypic variations in taste perception in a student population.
Prepare buffer solutions.
Understand restriction enzymes and their use in molecular biology labs.
Understand PCR and its application in molecular biology.
Understand SNPs (single nucleotide polymorphisms) and their role.
Explain DNA analysis by gel electrophoresis.
Understand data analysis techniques.
Explain experimental results.
Use R for statistical analysis.

Lab Schedule (Weeks 1-6)

Weeks 2, 3, 5: Laboratory skills focused on Pipetting, TE Buffer preparation, Numeracy, PTC taste tests, food preferences, and gel loading for the PTC1 and PTC3, involving agarose gel electrophoresis, and understanding bioinformatics.
Week 4: PTC 2, focusing on agarose gel electrophoresis and PCR product clean-up.
Week 6: Data Analysis & Computer Lab, focusing on reflecting on skills and articulating skills.
Week 7: Reflect on previously learned skills and articulating skills learned.
Week 8: Networking online to stand out for potential employers.

Practical Skills Monitoring in 2X

GTA observes skills in the lab.
Lab skills are practiced and developed.
Relevant skills development is tracked.
Practical skill development is recorded on a checklist on Moodle.
Skills achievements are on HEAR transcripts.
Six skills are assessed across the labs.
Pipetting
DNA gel loading
Changing pH of a solution
Using a centrifuge
Data analysis using R
Creating a professional LinkedIn profile

What is PTC?

PTC is phenylthiocarbamide.
It shares a similar chemical group with vegetables from the Brassica family.
Approximately 70% of the population can taste it as bitter.

Why Can Some People Taste PTC?

TAS2R38 gene on chromosome 7 determines PTC taste ability.
Variations in the gene sequence can lead to different phenotypes (taster vs non-taster).

Bitter Taste Discovery

Inability to taste PTC is a genetic trait that varies between individuals.

Bitter Taste Process

Taste buds are found on the tongue, in papillae.
Specific taste receptor cells respond to taste stimuli, such as bitter compounds.
These cells are linked to gustatory nerves.

Bitter Taste Process (TAS2R38)

TAS2R38 encodes a protein receptor.
Bitterness is perceived through a G protein-coupled second messenger pathway.
Variations in the TAS2R38 gene sequence lead to 'taster' or 'non-taster' phenotypes.
Three nucleotide positions were identified that make differences in the gene sequences.

Position SNPs in TAS2R38 Gene (taster vs non-taster)

145 position: C (proline) vs G (alanine)
785 position: C (alanine) vs T (valine)
886 position: G (valine) vs A (isoleucine)
Genotypes: TT (strong taster), tt (non-taster), Tt (weak taster).

Overview of Experimental Plan

Extract DNA.
Design PCR with primers to amplify TAS2R38 gene region (including SNP).
Perform PCR.
Digest PCR products with Fnu4H1 restriction enzyme to identify SNPs.
Analyze DNA fragments using gel electrophoresis.

Polymerase Chain Reaction (PCR)

Amplify DNA using PCR
This includes a template DNA sample (buccal swab), primers (forward & reverse), Taq polymerase enzyme, and dNTPs
The process is repeated.

Materials in PCR

Template to be amplified (genomic DNA from a mouth swab).
Forward and reverse primers.
Taq DNA polymerase.
Deoxynucleotide triphosphates (dNTPs).
Buffer to maintain pH and provide Mg2+.

Amplifying TAS2R38 Using PCR

PCR primers amplify 312 base pairs of the TAS2R38 gene, which have a SNP position of 785.
The amplified region is 312 base pairs in length.

Restriction Endonucleases

Restriction enzymes cut DNA at specific nucleotide sequences (restriction sites).
Fnu4H1 enzyme used is at a recognition site GCNGC.
TAS2R38 gene is cut at this site only.
Single nucleotide polymorphisms can affect the restriction enzymes.

Restriction Digest of SNP 785 with Fnu4H1

PCR product is 312 base pairs long.
The Fnu4H1 restriction enzyme digests specific sequences of DNA.
This results in different fragment sizes for taster and non-taster alleles.

Genotype Analysis

Determining the TAS2R38 genotype using gel electrophoresis.
The analysis involves digesting PCR fragments to reveal specific fragment lengths.

Lab Report

The lab report should determine whether there is a link between PTC taster genotype and other chosen variables.
Report components include an abstract, introduction, methods, results, discussion, and references.

Science News Essay

500 word essay +/- 10%.
Deadline 14th Oct.
Use reliable 2023/2024 sources and link them to your chosen molecular biology field.

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Description

This quiz covers the aims and operations of labs in the FTIB course, focusing on the perception of bitter taste and the genetic factors involved, specifically the SNPs in the TAS2R38 gene. It also emphasizes health and safety protocols necessary for laboratory work. Prepare to explore both phenotypic and genotypic variations among students.