"Hello class I'm Mrs. Prase, and welcome to Spectrum Science! I know there are only a few of you, but that won't limit the field trips and fun we'll have this year. Let's all introduce ourselves, then get started learning!"

I'm Celline!

I'm Matt!

I'm Hannah!

Meet the Class!

I have a question, Mrs. Prase! I have always wondered this; I have an older sister, Gina, who looks nothing like me! Why are we not identical?

Great question, Hannah! You must have read ahead on the syllabus, as that topic will be our first lesson and field trip! Mitosis and meiosis!!!!!

Today class, we will take a field trip to Hannah's cells to determine why she is not identical to her sister, despite having the same parents!

Hannah, we will have to take a trip to your cells to get a closer look, and really understand this topic!

Alright guys our first field trip will be inside Hannah to answer her question!

HUH?!

Let's go guys! Into the Magic Train!

Now that we are inside Hannah's body, let's take a look at her cells, and how cell division occurs.

The first step of cell division is known as "mitosis". Mitosis is the division of the nucleus. The purpose of mitosis is so that the body can grow and repair itself, and allow cells to divide when they become too large.

Let's take a closer look into the steps of mitosis...

Mitosis occurs in four stages, known as PMAT. The phases are prohase, metaphase, anaphase, and telophase.

Prophase is when the nuclear membrane and nucleolus break down, and chromosomes and spindles form. Metaphase is when chromosomes line up in the middle of the cell. Anaphase is when the centromere splits and spindle fibers pull sister chromatids away from each other. Telophase is a reversed prophase, where the nuclear membrane and nucleolus form, chromosomes unwind, and the spindles break down.

Mitosis only has one round of division, and 46 chromosomes, and it produces two identical diploid cells.

What are diploid cells?

Diploid cells are two copies of each chromosome. The human diploid number is 46. Haploid cells are only one copy of each chromosome, with a number of 23.

Mitosis ends with a phase of cytokinesis. Cytokinesis is the division of the cytoplasm.

This is so fascinating, Mrs. Prase!

After mitosis, is when meiosis occurs ! Meiosis's purpose is to the divide and separate the homologous chromosomes and sister chromatids.

Unlike mitosis, meiosis occurs in two rounds of division. The first stage, meiosis I, serves to separate the homologous chromosomes.

Mrs. Prase, what's a homologous chromosome?

Well Celline, homologous chromosomes are non-identical chromosomes containing the same types of genes, one gene from mom, and one gene from dad. This is helping to answer Hannah's question!

Homologous chromosomes are held together by a centromere, a structure that holds the two sister chromatids together.