The Story Behind Your Features

You might’ve noticed that you have your mom’s eyes. Or your dad’s. The shape of your ear might be similar to only a few other relatives. Your hair is curly and so is your grandmother’s! This is not just random, and there is a reason why your traits are similar to your family!

In 1856, a man named Gregor Mendel noticed that some peas were round, while others were wrinkled. He wondered if there was some reason as to why this was happening. He then started an experiment soon after to see if he could find a pattern. His first set of experiments included the flowers of the plants, and he compared their colors. He started out with purple and white pea flowers, and cross pollinated them. Their offspring, to his surprise were all purple! He then let the second generation of flowers pollinate within themselves, and even more to his surprise, for every 3 purple flowers, there was 1 white flower. Even though all the parent flowers were purple, some flowers ended up white. This showed that the purple flowers somehow carried a gene for the white color. This confirmed his hypothesis that the white gene was carried on through the generation of all purple flowers, even though those flowers did not show the white gene. He concluded that certain traits were dominant over others, and those traits show up more frequently than the recessive trait. In this case, the purple color was dominant over the white color. Usually, the dominant trait is denoted by a pair of capital letters, and the recessive trait is denoted by a pair of the same lower case letter. For example, in Gregor Mendel’s experiment, in his first batch of flowers, the purple ones were (PP) and the white ones were (pp). Additionally, when there is a case where there is one capital letter and one lower case letter (Pp), the dominant trait will always show. 

How does this relate to you? Let’s cover some basic genetic words before we get into the interesting stuff. 

Trait - The characteristic that you show. Eg. blue eyes, brown hair, attached earlobes, etc.

Genotype - The specific genetic coding of an individual’s traits. These are usually denoted with upper and lower case letters. Eg. Bb, MM, gg, Tt, etc.

Phenotype - A single trait or a group of traits, used to show which trait appears on an organism. Eg. Bb will have the same phenotype as BB, because they are both the dominant trait, and will show the same features. 

Punnett Square - A diagram used to predict the outcome of a certain trait using the genotypes of the parents’.

Looking at the punnett square above, we can see that in all 4 outcomes, the offspring will have brown eyes. However, on 2 of the 4 outcomes, the offspring will contain the gene for the blue eyes to be passed on in future generations. 

You can use this diagram to predict more traits such as hair color, blood type, ear shape, and so on. Try to figure out the genotypes of you and your parents’ by working backward!

Human Genome

Picture Source: Genesandhealth.org