“So what’s different about Mitosis versus Meiosis?”
Well looking at the picture we see Mitosis on the left… There is a single cell, which duplicates its chromosomes, divides, and the result are two cells identical to the parent cell.
Meiosis, on the right, all those same steps occur… BUT THEN! Another cell division occurs! We do PMAT a second Time (Thats Cray-Cray Mr. K)! The result then are 4 cells, with half the number of chromosomes, and each one has a unique set of chromosomes.
I know what you’re thinking… “But why would we only need half the number of chromosomes? Doesn’t each one of the cells of our body need all 46 chromosomes!?”
It is true that each one of our Somatic, or Body, cells needs a complete set of chromosomes. But our Gametes, or Sex Cells, only need half the number of chromosomes. This is known as being Haploid, or having one set of chromosomes. And I bet you already know why! That’s right, the other half comes from the 2nd parent during sexual reproduction (That’s off the chain Mr. K). When the male and female gametes meet (Fertilization), they combine to form one new cell called a Zygote that has two sets of chromosomes, one from Mom and one from Dad. This is known as being Diploid.
The Red X and the Blue X are duplicated chromosomes. During Prophase 1, they sometimes “Switch Legs”. This is known as Crossing Over.
The coolest part about the whole process is that it makes you Unique. And not in the Sesame Street, “You are special,” kind of way. More like, there are more than 8 million different genetic combinations that you can create in each of your gametes and they are assorted completely randomly (Independent Assortment), meaning that for each of your 23 pairs, you can give either one of the chromosomes, its not predetermined! And sometimes, Duplicated Chromosomes will even switch pieces (Crossing Over) making them even more unique!
All in all, Meiosis is a pretty unique process and I hope you enjoy learing about it as much as I enjoy teaching it! To learn more about Meiosis and how it causes genetic variation, check out my YouTube video below!