Unit 2 is about chromosomes and cell division. DNA winds around proteins in the cell called histones. When this happens, they take the shape of a chromosome. Humans have 46 chromosomes in their body cells and 23 in the reproductive cells (egg cells for females, sperm cells for males). Our genetic information comes from our parents, and when they combine they make up our traits. Remember though-it all goes back to the DNA!

There are two types of cell division that humans can undergo: mitosis and meiosis. Mitosis is the type of division that produces body cells. The cell grows, replicates its DNA, and then divides through a series of "steps" to make two identical cells-prophase, metaphase, anaphase, and telophase. Final cytoplasmic division occurs with cytokinesis. While this process doesn't truly happen in steps, we have given the division these names to help us identify the various things that are occurring in the cell during this division.

Meiosis is a division to produce gametes (sex cells). There are actually two divisions that occur because with this process the goal is to make 4 genetically different cells (as opposed to the two genetically identical cells produced by mitosis). The cell will undergo prophase, metaphase, anaphase, telophase, and cytokinesis a first time, which we will signify with a "I", and then undergo the process again with prophase II, metaphase II, anaphase II, telophase II, and cytokinesis.

Summary of each mitotic phase:
-Prophase: Nucleus dissolves, chromosomes tighten from chromatin, centrioles begin to move apart, spindle fibers appear
-Metaphase: Chromosomes align in the middle of the cell
-Anaphase: Chromosomes divide, one copy of each going toward opposite sides of the cell
-Telophase: Nucleus reforms, chromosomes unravel, spindle fibers dissolve
*Interphase and Cytokinesis are NOT a part of mitosis. They are simply stages that occur before and after.

By the end you have created four genetically different cells. See below for results of males vs. females

Oogenesis and Spermatogenesis:
Spermatogensis & Oogenesis.GIF

Worksheets for Chromosomes and Cell Division:

Video Summaries:
Chromosome Summary

What is a Chromosome-Bozeman

Cell Cycle and Mitosis Summary

Meiosis Summary