PTC lab

By: Hope Manion

What is the PTC gene?

The PTC gene is an old gene that isn't really needed anymore my modern day humans. But the reason that some people may have it is because it was used by ancestors millions of years ago. Scientists say that the gene was used to help decipher poisonous plants. If the plant was toxic, it would have extremely bitter taste, and therefore not appealing to eat. Those who had the gene would know to avoid those bitter plants and survive to reproduce, while those who didn't would die.

Genotype and Phenotype

The genotype of an organism is their genetic makeup while the phenotype of an organism is their physical characteristics.

PTC gene

TT- Taster. Those with the homozygous dominant trait usually taste extreme bitterness

Tt- Taster, those with the heterozygous trait can still taste bitterness, but it isn't as strong

tt- Non-taster. Those with the homozygous recessive trait can't taste anything.

How Do You Get The Trait?

PTC is a Mendelian allele. This means that if a child receives the dominant allele from either of his/her parents will have the dominant phonetic form of the trait. In PTC, it means that the child will be a taster. Only it receives both recessive allele will the child show the recessive phonetic form.

The control group

To see if you have the PTC gene, you have to run a lab.

During the experiment we first tested to see our phenotype. You must used a control in the experiment so that you can have a comparison to what would normally happen to what happens when you change something in the experiment. For this specifically, the control would be a piece of regular paper and the alternate would be the PTC paper.


PCR is an essential part of the experiment. PCR stands for polymerase Chain Reaction. It's job is to to amplify the DNA sample. It makes thousands, even up to millions of copies of the DNA sequence.

Next step

After the DNA is amplified, primer, master and restriction enzymes are added to the DNA sample. The primer is used to start DNA synthesis. The master is responsible for adding new nucleotides onto the parent DNA strand. Finally by adding the restriction enzymes, the DNA is cut into different sized pieces that can be used when performing the gel electrophoresis.

Structure of dna

DNA has a negative charge, so when it is put into the slots of gel electrophoresis, it moves slowly down the gradient towards the bottom where the charge is positive. Because it is cut into different sized pieces by the restriction enzymes, some are longer than other. Longer pieces stay closer to the top and they moves more slowly through the gel. While shorter pieces move farther and more quickly. You can figure out the genotype of an individual by looking at the placement of the DNA pieces in the gel.

flaws in the experiment

There are multiple things that you could have done wrong to mess of the experiment. One one the biggest flaws that could have been made is adding too much of any of the enzymes or mixing up DNA samples with another persons sample. That could be because you didn't label your tube, or because you didn't know how to correctly use the instruments given. It would completely mess up the results. One, you could get results that could be someone else. Or two, your results could be invalid because you added the wrong amount of a specific enzyme.