Reflecting on Genetics

After filling out the genetic trait chart in the Human Heredity lab for myself and my classmates, I used the data to predict whether each trait was dominant or recessive. I found that not all of my predictions were correct, in fact only two of my five predictions held true. This surprised me at first, but can be explained by the fact that our class of 14 kids is a very small sample pool compared to the census of millions of people that scientists must have taken to determine genes dominant or recessive. 6 out of 14 kids in our class could taste the PIC strips, so I predicted that it was a recessive trait. However it turns out that PIC tasting is a dominant trait, which didn't surprise me that much because 6 out of 14 is nearly half the class. 11 out of 14 kids in our class could roll their tongues, so it was easy to predict correctly that tongue-rolling is a dominant trait. Only 4 out of 14 kids in our class had attached ear lobes, so it was also easy to guess correctly that an attached ear lobe is a recessive trait. 7 out of 14 kids in our class had hitch hiker's thumbs, exactly half, so I just took a wild guess that it was a dominant trait, when in fact it turned out to be a recessive gene. Lastly and most surprisingly 6 out of 14 kids in our class had a widow's peak, so I predicted that it was a recessive trait, only to learn that it is a dominant trait. This surprised me because I would expect at least half of our class to have a widow's peak if it is a dominant trait, but as Mrs. McCurdy explained, a widow's peak isn't exactly an admirable trait to have, and humans may have evolved through genetic variation so that fewer and fewer people have widow's peaks, even if it is indeed a dominant trait.

I am a tongue roller, have an attached ear lobe, have a hitch hiker's thumb, and have a widow's peak, and unfortunately for the sake of a more interesting pool of data, both of my parents share all of the same traits as me. I was able to deduct a few genotypes of the recessive traits I have from this lab though. Having attached ear lobes is a recessive trait that both my parents and I posses, therefore I know that we all must have an homozygous recessive aa genotype. Having hitch hiker's thumbs is also a recessive trait that both my parents and I posses, so I can conclude that we all must have a homozygous recessive hh genotype. As far as the tongue rolling and widow's peaks go, both my parents and I all have the dominant trait, so we all could be either homozygous dominant TT or heterozygous Tt, but there is no way of telling which without collecting data from previous generations.


Lastly, there were four Mendelian traits I found that surprised me while I was researching whether the traits in this lab were dominant or recessive. The first of the traits which surprised me was dimples. Dimples is a dominate trait, while I only know two people who have dimples, which is why the fact that it is a dominate trait surprised me so much. The second trait which surprised me was tall and short stature. I found that short stature was actually a dominate trait, which surprised me because most of the people I know desire to be tall, but we are naturally supposed to be short. I would have thought that humans would have evolved genetically overtime so that it would be a dominate trait to be tall, but tall stature is listed as a recessive trait. The third trait which shocked me was dwarfism. Dwarfism is a dominate trait, when in fact I am not aware of anyone in my life that has dwarfism. I assume that dwarfism is one of the traits that humans have evolved over time to avoid, because I know so few people who have dwarfism, or who desire to have dwarfism. The last and most shocking Mendelian trait that I found in my research was six fingers as opposed to the normal five fingers. Having six fingers per hand is the dominant trait, when in fact I don't know a single person who has six fingers, which is why it surprised me so much. I would assume that this is a trait that humans have evolved to avoid as well, which is a pattern that I'm starting to see with undesirable traits, and one that I'm sure i'll see more of as we continue with our genetics unit.  

Source for the Mendelian Traits:
http://education.sdsc.edu/download/enrich/mendelian_traits.pdf