What are we learning? Why are we learning this?
content, procedures, skills
Tier II: High frequency words used across content areas. Key to understanding directions, understanding relationships, and for making inferences.
Tier III: Low frequency, domain specific terms
Building on what we already know
What vocabulary & concepts were learned in earlier grades?
Make connections to prior lessons from this year.
This is where we start building from.
The cell cycle is a series of events involving cell growth and cell division. It produces two new daughter cells.
The cell cycle has two major phases: interphase and the mitotic phase.
During interphase, the cell grows and DNA is replicated.
During the mitotic phase, the replicated DNA and other cell contents are separated, and the cell divides.
Let’s start with a simple overview of the process from the Amoeba Sisters, Sarina Peterson (“Petunia”) and Brianna Rapini (“Pinky”.)
Now let’s look at each phase in more detail.
Here the cell takes in nutrients, grows, and preps for cell division.
G1 (Growth phase, or Gap phase)
Cell takes in nutrients.
Builds proteins, organelles, and grows in size.
S (synthesis phase)
DNA synthesis – The cell synthesizes a complete copy of the DNA. This is also called DNA replication.
In this phase the cell duplicates the centriole (centrosome,) so now we will have 2 of them.
These centrioles will separate the chromosomes (pull them apart) during M phase.
Here we see them duplicated (there are 2 of them!) but they aren’t yet doing anything.
Just minding their own business, floating in the cytoplasm. They’re in the cell, but outside the nucleus.
G2 (Growth phase 2, or gap phase 2)
Cell grows more. More protein synthesis, builds enzymes.
Makes more duplicates of some organelles.
The parent cell divides into 2 daughter cells. To see the entire process check out this video, NDSU VCell Production’s animation “Mitosis”.
Text in this lesson has been freely adapted by RDK from “The cell cycle, OpenStax College, Biology
Let’s rest: the G0 phase
Some cells stop this cycle of growth and mitosis. Instead, they enter a mature, adult state and stay that way. The cell is no longer preparing to divide.
This is the G0 phase.
Some people call this a post-mitotic state.
We see this in nerve and heart muscle cells. Many stem cells stay in this state until their are needed.
They are fully developed, and then do their job for the rest of their life.
Comparing mitosis with meiosis
When learning about reproduction, you may already have learned about meiosis. This is the process by which one gamete cell (a proto-sperm or proto-egg) becomes 4 daughter cells.
Here is a comparison of mitosis and meiosis from the Amoeba Sisters, Sarina Peterson (“Petunia”) and Brianna Rapini (“Pinky”.)