The Beauty of Genetics
Have you ever wondered how you got your looks? Why you have blue eyes when your brother has brown eyes, or why your sister is a red-head when no one else in the family is. Why you may be left-handed, but both your parents are right-handed. All of your basic characteristics- hair color, eye color, hand dominance, etc.- come from your genes. These genes are found in every cell, and help tell the cell what it should be doing. So where do these genes come from? How did you get this unique set of instructions that make you who you are? It’s simple- they came from your parents!
When you were just a tiny baby being formed, your own set of chromosomes- structures that have genes within them- were being created by combining your mom and your dad’s. Half of your mom’s chromosomes and half of your dad’s were put together and that’s where you got your set from. The photo below shows our basic chromosomal make-up. Half of the chromosomes are dark green- showing they came from one parent. The other half are lighter green- showing they all came from the other parent. As you developed, your unique set of genes within the chromosomes helped form your basic characteristics. This may explain why you have your mom’s eyes or your dad’s nose.
Every person has a total of 46 chromosomes; they are set in pairs numbered 1-23. With the exception of chromosome 23, each pair looks identical to each other. Chromosome 23 is special in that this chromosome determines a person’s gender. If the person is female, they have two X chromosomes, and they’ll be identical. If the person is male, however, they’ll have an X and a Y chromosome, and look completely different! Within chromosomes, we find our genes- the special set of instructions that tell cells what to do and how to look. The information within these genes helps determine what traits we show from our mom and dad.
When we look at the basic characteristics that genes code for, we can see that some are a lot more common than others. For example, brown eyes are a lot more commonly seen than blue or green eyes. Brown hair is a lot more common than blonde, or red. Being right-handed is a lot more common than being left-handed. These all can be explained by what genes you inherited (received) from your parents, and whether it is a dominant copy or a recessive copy.
Dominant genes are the showboat. When a dominant gene is found, you know it. Regardless of if there are two copies of the dominant gene, or just one, if it’s there its being expressed. They overpower the other gene and make sure they’re shown. Some examples of dominant genes are those for brown hair, brown eyes, or right-handedness. When you see these kinds of characteristics, though, you don’t automatically know if they have two dominant genes, or one dominant and one recessive. Since it only takes one to shine, it’s harder to figure out what it has by its side.
Recessive genes are a little more shy, but easier to figure out. Recessive genes need two copies in order to show their stuff; if a dominant gene is there, they don’t get their moment. When there are no dominant genes, however, the recessive genes get their time to shine. Some examples of recessive genes include those for blue eyes, red hair, or left-handedness. If you see someone with these kinds of characteristics, you know they’ve got two recessive copies.
When someone has two of the same copies of a gene, it's called being homozygous. This happens when they have two dominant or recessive copies of a gene. When they have one dominant copy and one recessive copy, it's called being heterozygous.
In the photo above, you can see examples of what homozygous and heterozygous chromosome pairs look like. You can also see which gene is the dominant one, and which is the recessive one. In many cases, including the one above, a capital letter is used to show the dominant gene, and a lowercase letter is used to show a recessive gene. So here, B is the dominant gene, and b is the recessive gene. The pair on the left is homozygous for the dominant BB gene, and the pair on the right is homozygous for the recessive bb gene. The two pairs in the middle are both heterozygous; even though one is written Bb and the other is bB, they have the same overall outcome of being heterozygous.
Whether you have all dominant genes, all recessive genes, or a mix of both- these genes all make you the unique person you are. They are there to help you shine and be the best person you can be!
As a fun activity one day, try to figure out what dominant and recessive characteristics you have, and if your parents or siblings have the same ones as you! You can find more examples of dominant and recessive traits by going to the website below:
References
Biology for Kids. (n.d.). Retrieved September 19, 2020, from https://www.ducksters.com/science/biology/chromosomes.php