Cell Division Day 1

The Cell Cycle:
How/Why Cells Divide

Hotspot

Select the organelle that contains all genetic information in the cell

Hotspot

Select the organelle that directs/controls all cell functions

Hotspot

Select the organelle that assists with cell division in animal cells

Labelling

Label the following terms: Cell, DNA, Chromosome, Nucleus, Gene

Drag labels to their correct position on the image

cell

nucleus

gene

DNA

chromosome

The Cell Cycle

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The Cell Cycle

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​Interphase	​Cell does normal cell things, lives its life
​G1	​This is part of interphase. Organelles double
​S	​This is part of interphase. DNA Replicates
​G2	​This is part of interphase. Proteins are made
M	​Mitosis
​C	​Cytokinesis

Why do Cells Divide?

For a few reasons.

1. They need to stay small

   Remember: Surface Area/Volume Ratio. The greater the surface area, the faster and more efficiently materials can be transported in and out of the cell.

2. Increasing the number of cells allows for multicellular organisms to grow

3. Replacing/Repairing Damaged Tissues

4. Reproduction

How does Cell Division Start?

In order to understand this, we should take a closer look inside a cell’s nucleus.

The nucleus of a cell controls its activities, and the genetic traits of an organism. Each nucleus contains structures called Chromosomes, which are composed mainly of DNA.
DNA consists of long chains of Nucleotides that are organized into a twisted ladder shape known as a double helix.

Organization of Genetic Information

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How is DNA Packaged?

DNA is packed into chromosomes; more or less it's to take up less space, think of it like curl shrinkage. The twisted/curly version takes up less space than the straightened version

After replication, a chromosome is double stranded. Each strand is a long, twisting, curly molecule of DNA. The two identical strands are called chromatids They are joined by a centromere

How is DNA Packaged?

Chromosomes are only present during cell division. During interphase, the DNA is in a relaxed state called Chromatin. This is the "brushed out" version of the "curly hair".

Chromatin

Chromosomes

Multiple Choice

When do chromosomes become visible under a microscope?

• During DNA replication
• When cells are dividing
• During transcription
• In the resting phase of the cell cycle

Labelling

Label the following image. Place the labels to the right of each number.

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centromere

chromosomes

chromatids

Match

Match the following

• Chromatid

• Chromatin

• chromosome

• homologous chromosomes

• Sister chromatids

half of a chromosome

loose strands of DNA

tightly coiled duplicated DNA

2 chromosomes that have similar genes

2 identical halves of a chromosome

• half of a chromosome

• loose strands of DNA

• tightly coiled duplicated DNA

• 2 chromosomes that have similar genes

• 2 identical halves of a chromosome

Multiple Choice

Structure A refers to the _____.

• chromatid
• chromosome
• centromere

Multiple Choice

Structure (b) is a ____.

• chromosome
• chromatid
• centromere

Multiple Choice

Structure (c) is a ____. Hint: It is one half of the X shape.

• chromosome

• sister chromatid

• centromere

Multiple Choice

What is structure D?

• homologous chromosomes

• sister chromatids

• genes

• DNA

Multiple Choice

What is structure C?

• sister chromatids

• centromeres

• homologous chromosomes

• DNA

How many Chromosomes?

Each organism on Earth has their own special chromosome number. Since we're talking in such broad terms, let's call the magic number of chromosomes n.

So, you know how you need 2 biological parents to make an offspring? This is because each offspring gets 1 n from each parent.

Mom gives offspring 1n

Dad gives offspring 1n

Offspring will have how many n?

Categorize

Options (4)

"half" cell

"full" cell

1 set of DNA

2 sets of DNA

Organize these options into the right categories

Haploid

Diploid

How many Chromosomes?

The ONLY Haploid (1n) Cells are Eggs and Sperm

AKA Gametes or Sex Cells

This is because Haploid (1n) + Haploid (1n) = Diploid (2n)

Egg (1n) + Sperm (1n) = Zygote (2n)




EVERY OTHER CELL
(Somatic Cell/Body Cell) is Diploid

Multiple Choice

Human Diploid # is

• 2n, 46 chromosomes

• 1n, 23 chromosomes

What happens in the Cell Cycle?

G1 Checkpoint: -Cell size is adequate -Growth factors are present

G2 Checkpoint: -Cell size is adequate -DNA replication is successfully completed

M Checkpoint: -All chromosomes are attached to spindle fibers

Labelling

Label each stage with its description.

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the cell is growing

the cell divides

DNA is copied

The cell prepares to divide

Multiple Choice

During which parts of the cell cycle does the cell grow?

• G1 and G2
• G1 and S
• M phase and cytokinesis

Enough about Chromosomes, let's split!

Enough about Chromosomes, let's split!

So, Cytokinesis?

Cyto=Cytoplasm
Kinesis=Split

The cytoplasm literally separates/splits to form two new cells called daughter cells.
In animal cells, cytokinesis occurs by constriction (pinching) of the cell membrane in the middle of the cell called Cleavage.

In plant cells, a dividing wall called the Cell Plate begins to grow from the center outward at the middle (equator) of the cell. It becomes a new cell wall that separates the two new cells.

What if something goes wrong?

The cell cycle determines the rate of cell division. As a result, it is closely monitored and regulated by the body. Each cell contains specific genes (DNA sequences) which control the length of each stage of the cell cycle.

However, mistakes happen. Sometimes the body loses control of the cell cycle, which may result in the development of cancer.
Cancer is caused by abnormal, rapid, and uncontrolled cell division. As a result, a tumor, or clump of cells develops.
There are two kinds of tumors:
Benign Tumors- Do not invade surrounding tissues. They just sit there...
Malignant Tumors- Spread into other tissues and can interfere with organ function.
Cyclins are a group of proteins that regulate the timing of the cell cycle in eukaryotic cells.

What if something goes wrong?

Types of Cell Division

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Copy this table. Show me your completed table before you pack up