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Copy of Testing Your Taste: PTC (Taster) Gene Phenotype & Genotype Analysis

For Smith College Interterm Science Teaching Internship at the Northampton High School.

Arcadia Kratkiewicz

on 4 February 2013

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Transcript of Copy of Testing Your Taste: PTC (Taster) Gene Phenotype & Genotype Analysis

PTC (Taster) Gene Phenotype & Genotype Analysis Testing Your Taste -Nontasters: no target region, one long uncut DNA fragment (303 base pairs)

-Homozygous tasters: only cut DNA, two different length fragments (238 and 65 bp)

-Heterozygous tasters: some cut DNA & some uncut DNA, all three lengths (303, 238, and 65 bp) Results of Electrophoresis 1, 4, 6, 9- heterozygous tasters Results of Electrophoresis A restriction enzyme recognizes and cuts
a unique sequence of nucleotides in DNA Restriction enzymes were originally found in bacteria as a part of their immune system. They are used to cut up phage DNA so it cannot be incorporated into the bacterial genome. We are using the restrition enzyme:
Fnu4HI Fnu4HI recognizes the sequence: 5' - GC NGC - 3' 3' - CGN CG - 5' Tasters will contain an Fnu4HI site Non-tasters will not contain the Fnu4HI site Tasters will have
their DNA cut by the restriction enzyme Non-tasters DNA will remain the same length Non-taster DNA = 303 base pairs

Homozygous Taster = 238 + 65 base pairs

Heterozygous Taster = 303 + 238 + 65 base pairs 2, 3, 8- nontasters 5- homozygous taster 7- blank 10- ladder PCR Overview = Nucleotide
Difference = Fnu4HI Site 1. Determine PTC Taster Phenotype
2. DNA Extraction
3. PCR
4. Restriction Enzyme Digest
5. Gel Electrophoresis
6. Determine Your Genotype 1 2 3 4 5 6 7 8 9 10 Non-taster gene Taster Allele -dominant
-codes for taste receptors that can bind to PTC
-binding sends "bitter" signal to brain Non-Taster Allele -recessive
-codes for taste receptors that cannot bind to PTC -PTC discovered in 1931 by Arthur Fox
-Ability to taste PTC determined by a single gene that codes for a taste receptor on the tongue
-2003: TAS2R38 discovered
-2 common forms: tasting and non-tasting allele
-Codes for bitter taste receptor protein with slightly different shape
-Receptor shape determines how strongly it can bind to PTC
-75% can taste PTC -“Strong tasters” are less likely to be smokers

-May be more sensitive to certain foods like coffee, cilantro, or other strong flavors PTC and Evolution -The bitterness tasted by tasters kept early humans from eating poisonous plants, but they were pickier eaters and may not have thrived during famine
-Non-tasters may taste a different bitter compound
-Heterozygotes have the best of both worlds: one tasting allele and one non-tasting allele. PTC and Animals -Chimpanzees are tasters or non-tasters just like humans
-But, Chimps can taste based on a different genetic mutation than humans
-This shows that we may have had similar selection factors in our evolution. Supertaster http://genetics.thetech.org/online-exhibits/are-you-super-taster http://genetics.thetech.org/online-exhibits/ptc-tasting Kary Mullis won the Nobel Prize for Chemistry in 1993 for his invention of, and work on PCR. PCR Fun Facts!
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