How and why do some people like certain foods and not others?
Taste receptor 2 member 38 (TAS3R38) is a protein that in humans is encoded by the TAS2R38 gene. TAS2R38 is a bitter taste receptor, with different genotypes associated with that ability to taste 6-n-propylthiouracil (PROP) and phenylthiocarbamide (PTC). While scientists have long hypothesized that different taste receptor genotypes could influence tasting ability, TAS2R38 is one of the only taste receptors shown to have this function.
In humans, the dominant form of the TAS3R38 gene, “T,” codes for the ability to taste bitter substances like PTC. The human taster “T” phenotype is associated with the sequence “PAV” – or more specifically P49, A262 and V296. In other words, human tasters have a P (Proline) at position 49, an A (Alanine) at position 262, and a V (Valine) at position 296. Non-tasters (with the genotype “tt” )are associated with “AVI” at these same positions.
The Basic Local Alignment Search Tool (BLAST) is a bioinformatics tool that scientists use to study and compare DNA and protein sequences. In this activity, students use BLAST to compare the TAS3R38 protein sequences from humans and non-human primates to answer the following research question:
Are primate species other than humans “tasters” or “non-tasters”?
Download Predicting PTC Tasting Ability among Primates Instructions (pdf, Class Set)
Download Predicting PTC Tasting Ability among Primates Worksheet (pdf, Print a Copy for Each Student)
Download All TARSR38 Protein Sequences (docx)
Download Codons and Amino Acid Chemistries (pdf)
Download Primate Cards (pdf)
Making a multiple alignment and phylogenetic tree **NEW** |
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1. Click primates_bear.txt The file will open in a new window. If you scan the sequences, you can find the amino acids that indicate taster or non-taster by comparing the first two rows (human taster vs. human non-taster). Tasters have a Proline at position 49, an Alanine at 262, and a Valine at 296. 7. To make a phylogenetic tree, click Phylogenetic Tree. 8. Find the polar bear sequence near the top of the tree. Hold the cursor over the dot near the sequence. You should see a menu appear. Select Reroot Tree to set the polar bear sequence as the outgroup. Outgroups are sequences that are more distantly related. Scientists use outgroups as a reference point when they make phylogenetic trees. 9. Evaluate the tree. |
Note to Teachers: There are currently 20 Primate Cards available for download [associated with Non-Human Primate sequences 1-20 below].
Image Credits for Primate Cards
- "Agilegibbon" by Julielangford - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Agilegibbon.jpg
- "Agile Gibbon area" by IUCN Red List of Threatened Species, species assessors and the authors of the spatial data.. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Agile_Gibbon_area.png
- "Allens swamp monkey" by Grendelkhan - Own work. Also available from my Flickr.. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Allens_swamp_monkey.jpg
- "Allen's Swamp Monkey area" by IUCN Red List of Threatened Species, species assessors and the authors of the spatial data.. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Allen%27s_Swamp_Monkey_area.png
- "Angola Colobus area" by IUCN Red List of Threatened Species, species assessors and the authors of the spatial data https://commons.wikimedia.org/wiki/File:Angola_Colobus_area.png
- "Colobus angolensis" by Ryan E. Poplin - Angola Colobus Monkey #6. https://commons.wikimedia.org/wiki/File:Colobus_angolensis.jpg
- "Aotus azarae infulatus" by Rich Hoyer - Flickr. Licensed under CC BY 2.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Aotus_azarae_infulatus.jpg
- "Azara's Night Monkey area" by IUCN Red List of Threatened Species, species assessors and the authors of the spatial data.. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Azara%27s_Night_Monkey_area.png
- "2011 Colobus guereza cropped2" by 2011_Colobus_polykomos.JPG: J. Patrick Fischerderivative work: Hic et nunc (talk) - This file was derived from: 2011 Colobus polykomos.JPG:. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:2011_Colobus_guereza_cropped2.jpg
- "Mantled Guereza area" by IUCN Red List of Threatened Species, species assessors and the authors of the spatial data.. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Mantled_Guereza_area.png
- "Black-capped Squirrel Monkeys in tree". Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Black-capped_Squirrel_Monkeys_in_tree.JPG
- "Saimiri boliviensis distribution" by IUCN Red List of Threatened Species, species assessors and the authors of the spatial data.. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Saimiri_boliviensis_distribution.svg
- "Pan paniscus (female)" by © Hans Hillewaert /. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Pan_paniscus_(female).jpg
- "Bonobo distribution" by Africa_map_blank.svg: Eric Gaba (Sting - fr:Sting)derivative work: Alphathon /'æl.f'æ.ðɒn/ (talk) - Africa_map_blank.svg. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Bonobo_distribution.svg
- "Orang Utan, Semenggok Forest Reserve, Sarawak, Borneo, Malaysia" by Eleifert - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Orang_Utan,_Semenggok_Forest_Reserve,_Sarawak,_Borneo,_Malaysia.JPG
- "Mapa distribuicao pongo pygmaeus" by Udo Schröter - Own work. Licensed under Public Domain via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Mapa_distribuicao_pongo_pygmaeus.png
- "Brown-mantled Tamarin" by D. Gordon E. Robertson - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Brown-mantled_Tamarin.jpg
- "Saguinus fuscicollis distribution" by IUCN Red List of Threatened Species, species assessors and the authors of the spatial data.. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Saguinus_fuscicollis_distribution.svg
- Self-portrait of a female Celebes crested macaque (Macaca nigra) in North Sulawesi, Indonesia, who had picked up photographer David Slater's camera and photographed herself with it.
- "Celebes Crested Macaque area" by IUCN Red List of Threatened Species, species assessors and the authors of the spatial data. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Celebes_Crested_Macaque_area.png
- "Schimpanse Zoo Leipzig" by Thomas Lersch - Own work. Licensed under CC BY 2.5 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Schimpanse_Zoo_Leipzig.jpg
- "Pan troglodytes area" by User:Luis Fernández García - Information from Keele & al. (2006). Chimpanzee Reservoirs of Pandemic and Nonpandemic HIV-1. Scienceexpress. 25 May 2006. Map base from Image:World_map_blank_black_lines_4500px.gif.. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Pan_troglodytes_area.png
- "Weißbüschelaffe (Callithrix jacchus)" by © Raimond Spekking / CC BY-SA 4.0 (via Wikimedia Commons). Licensed under CC BY-SA 4.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Wei%C3%9Fb%C3%BCschelaffe_(Callithrix_jacchus).jpg
- "Callithrix jacchus distribution" by IUCN Red List of Threatened Species, species assessors and the authors of the spatial data.. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Callithrix_jacchus_distribution.svg
- "Mono ardilla - Saimiri sciureus" by ggallice (Geoff Gallice) - http://www.flickr.com/photos/dejeuxx/5402796579/. Licensed under CC BY 2.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Mono_ardilla_-_Saimiri_sciureus.jpg
- "Saimiri sciureus distribution" by IUCN Red List of Threatened Species, species assessors and the authors of the spatial data.. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Saimiri_sciureus_distribution.svg
- "Drill Lincolnparkzoo" by Grendelkhan - Own work. Also available from my Flickr.. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Drill_Lincolnparkzoo.jpg
- "Drill range map" by Bamse - self-made based on CITES data and using a blank map of Africa from commons. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Drill_range_map.svg
- "Trachypithecus francoisi los angeles zoo" by Junkyardsparkle - Own work. Licensed under CC0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Trachypithecus_francoisi_los_angeles_zoo.jpg
- "Trachypithecus francoisi distribution" by IUCN Red List of Threatened Species, species assessors and the authors of the spatial data.. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Trachypithecus_francoisi_distribution.svg
- "Golden Snub-nosed Monkeys, Qinling Mountains - China" by Giovanni Mari - Flickr. Licensed under CC BY-SA 2.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Golden_Snub-nosed_Monkeys,_Qinling_Mountains_-_China.jpg
- "Golden Snub-nosed Monkey area" by IUCN Red List of Threatened Species, species assessors and the authors of the spatial data.. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Golden_Snub-nosed_Monkey_area.png
- "Gorilla gorilla at the Bronx Zoo 007" by Postdlf from w. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Gorilla_gorilla_at_the_Bronx_Zoo_007.jpg
- "Western Gorilla area" by IUCN Red List of Threatened Species, species assessors and the authors of the spatial data.. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Western_Gorilla_area.png
- "Bijilo-Portrait-of-a-Callithrix-Monkey" by Bjørn Christian Tørrissen - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Bijilo-Portrait-of-a-Callithrix-Monkey.jpg
- "Chlorocebus sabaeus distribution" by IUCN Red List of Threatened Species, species assessors and the authors of the spatial data.. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Chlorocebus_sabaeus_distribution.svg
- "AwasaVervet" by Joe Castleman (Gyrofrog) - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:AwasaVervet.jpg
- "Grivet area" by IUCN Red List of Threatened Species, species assessors and the authors of the spatial data.. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Grivet_area.png
- "Hamadryas baboon" by المُصوّر: مُعتز توفيق إغباريّة - Own work. Licensed under CC BY-SA 4.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Hamadryas_baboon.jpg
- "Hamadryas Baboon area" by IUCN Red List of Threatened Species, species assessors and the authors of the spatial data. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Hamadryas_Baboon_area.png
- "Snow Monkeys, Nagano, Japan" by Yblieb - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Snow_Monkeys,_Nagano,_Japan.JPG
- "Japanese Macaque area" by Termininja - Japanese macaques (Macaca fuscata). Licensed under GFDL via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Japanese_Macaque_area.svg
- "Colobus polykomos" by frank wouters - Flickr. Licensed under CC BY 2.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Colobus_polykomos.jpg
- "King Colobus area" by IUCN Red List of Threatened Species, species assessors and the authors of the spatial data.. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:King_Colobus_area.png