When I was young, I often wished that I had a twin. Books, movies, and twins in real life always fascinated me. Similar looks, fun pranks, and having a built-in best friend were things that I often associated with twins. However, when it really comes down to it, twins aren’t completely identical; differences in personality are clear, but no two twins have ever looked exactly the same. 

Why though?

Well, this question can be answered through meiosis, which I learned about in my AP Biology class this past month. Meiosis is the process by which cells divide to create “gametes (egg and sperm cells) for…reproduction”  (Fiveable). Gametes eventually form a zygote that develops into a living, breathing baby.

Meiosis is important because it is how humans have been produced for generations upon generations. In this process, genetic information is passed down from parents to offspring. But how come we aren’t identical copies of our parents? During meiosis, new gene combinations are formed in multiple phases.

First, in Prophase I, the first stage of meiosis, homologous chromosomes (pairs of chromosomes where one chromosome is from the mom, the other is from the dad) cross over and exchange segments to create  new versions of the chromosome. The chromosome that has a new mixture of the homologous chromosomes is passed down throughout meiosis. 

Later, in Metaphase I, genetic diversity is maintained through independent assortment. This means that when lined up in the middle of the cell, each homologous pair lines up with other pairs randomly.

Both of these processes are what make us different from each other, from our parents, and from our siblings. This is also why fraternal twins aren’t completely identical: they come from two different zygotes. Additionally, identical twins also aren’t completely identical. These types of twins come from the same egg that splits up, which is why they appear identical. However, the womb environment in which identical twins develop isn’t the same; one twin might have slightly better conditions than the other, which can lead to differences in height and weight, thus making identical twins not fully identical.

Overall, meiosis can often be another topic that is easily overlooked. However, the truth is, meiosis is the basis of humanity, and how reproduction continues. The next time you learn another science topic, don’t overlook it; instead, let it spark an interest and appreciation for life in you. 

That’s all, stay tuned for the next article!! 🙂

Sources: https://fiveable.me/ap-bio/unit-5/meiosis/study-guide/FC0aTuODYikjJuhlBO1Z