The Cell Cycle – Mitosis

What is happening inside the cell during asexual reproduction?

In order for a cell to divide, it must first grow and make a copy of every piece of DNA. It also must separate all

the chromosomes correctly so each new cell has a pair of each chromosome.

This entire process is called the CELL CYCLE.

There are 3 main parts: Interphase, Mitosis and Cytokinesis

1) Interphase

2) Mitosis

3) Cytokinesis

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The Cell Cycle – Step by Step

(A) INTERPHASE

The cell is growing and producing new materials in preparation

for cell division. Each strand of DNA is replicating during

interphase. The DNA cannot be seen at this time as it is uncoiled

in the form of chromatin (the threads are too small to see)

DID YOU KNOW?

You replace your stomach lining cells every days, your skin cells

every days, your red blood cells every days, and your liver

cells every days.

The cell cycle for your skin cells only takes hours!

Some terminology:

DNA duplicates

(B) MITOSIS & CYTOKINESIS

• the process involving the separation and division of chromosomes (DNA) and other cell contents.

• involves 4 stages: prophase, metaphase, anaphase, telophase (PMAT)

(1) PROPHASE

Chromatin (uncoiled, invisible DNA) coils up and forms

chromosomes (visible under the light microscope)

duplicated (identical) chromatids are joined together at the

centromere. Each is still called a chromosome

centrioles begin to move to opposite ends of the cell and spindle

fibers start to form between them.

nuclear membrane starts to disappear

(2) METAPHASE

Nuclear membrane completely disappears and the chromosomes

move out into the cytoplasm.

centromeres line up along the equator (centre) of the cell

centrioles send out spindle fibers which attach to the centromeres

(3) ANAPHASE

spindle fibers contract and pull the chromatids apart

chromatids separate and move toward opposite ends of the cell

cell now contains 2 identical sets of chromosomes moving to

opposite ends.

(4) TELOPHASE &CYTOKINESIS

chromosomes uncoil & disappear (can’t see with microscope)

new nuclear membranes form around the new sets of

chromosomes

cytokinesis is completed to produce 2 cells that are

identical to the original, parent cell

Cell Cycle Follow-up Questions

DID YOU KNOW?

☺ All steps of the cell cycle are monitored by proteins in the cell. These proteins communicate problems to the nucleus, such as:

(1) Not enough nutrients to support cell growth (2) DNA has not been replicated (3) DNA is damaged

☺ Despite the cell’s efforts to monitor the cell cycle, mistakes can happen. Sometimes, chromosomes do NOT separate equally.

This can result in daughter cells which contain MORE or LESS DNA than it should (Mutation!!)

1. List the 3 stages of the cell cycle and describe 2 events that happen during each stage.

# Stage Name Events That Occur During The Stage

1

2

3

2. Explain why the skin cells of a human must divide. 3. Why is it important for DNA replication to occur

before the cell divides?

4. During which stages in the cell cycle does each chromosome consist of two chromatids held together by a centromere?

5. What is the function of the spindle fibers?

6. List 5 terms associated with the Cell Cycle that start with the letter “C”. For each term, describe its role in the Cell Cycle.

Term With Name Starting With “C”

Role in the Cell Cycle

Chromatin

Chromosomes

Centriole

Centromere

Cytokinesis

7. A mnemonic is a sentence used to help you remember something. For example, the points on a compass can be

remembered by….”Never Eat Shredded Wheat” (North, East, South, West). Create a mnemonic for remembering the

stages of mitosis.