Mitosis. Asexual Reproduction

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Asexual Reproduction


Photosynthesis and Cellular Respiration and Plants Quiz

• Clear your desk except for a writing utensil

• Stay quiet through the quiz

• When finished, hold onto your quiz

• I will collect when everyone is done


Cell Cycle

• KlM



Work with your neighbor to think about why is it that

elephants aren’t furry, but other animals that live in the same environment, like lions and zebras, are furry?








Ideal “Elephant”

Surface Area (= a2 x 6)

= 3 x 3 x 6

= 54m2


= 3 x 3 x 3

= 27m3

Ideal “Lion”

Surface Area (= a2 x 6)

= 1 x 1 x 6

= 6m2


= 1 x 1 x 1

= 1m3 SA: Volume Ratio

Elephant 2:1

Lion 6:1

The elephant has less surface area per unit of volume to dissipate heat than a lion. Thus the elephant only has sparse

hairs to avoid overheating.

Think: Where is this analogy going regarding cells?





What must get in?

What must get out?


If a cell is too large, the SA:Volume ratio is too

small for diffusion to accommodate the requirements of the



So what does a cell do?

• When the cell reaches it’s maximum size, the cell will divide into two cells that are identical to each other and to the

original cell


What is mitosis?

Mitosis- is the division of a parent cell to form two identical daughter cells.

Cell Division = the process by which a cell divides into two daughter cells. Before division

occurs, a cell copies all of its DNA.


Before the details of mitosis…

• Do cells divide all the time?

• What factors cause cells to divide?

• Do different cells divide differently?

• What happens when cells keep dividing

when they aren’t suppose to?


What is the cells life cycle?

• G1 (Gap 1) Cell Growth

• S (Synthesis) - DNA copies

• G2 (Gap 2) - cell prepares for division and continues to grow

• M (Mitosis)- Cell condenses and separates DNA and

begins to pull apart.

• Cytokinesis- Cell splits.


Cells spend 90% of their time in Interphase. So what causes cells to


Single Cell Organisms

• Reproduction

Multi-cellular Organisms

• Growth

• Repair

• Note: multi-cellular organisms reproduce

through a separate cellular division process called

meiosis (we will cover that next unit!)


For single celled organisms…

• Reproduction


• Mitosis is a type of asexual reproduction.

• Asexual reproduction is a mode of reproduction by which offspring arise from a single parent

• Offspring have 100% of the DNA of the parent, in other words, they are exact “clones” of the

parent cell

• Unicellular (one celled) organisms use mitosis to reproduce.

– Example: Hydra budding.

What is Asexual



• Two major types, Mitosis and Binary Fission

• Mitosis occurs in eukaryotes, binary fission occurs in prokaryotes

– Binary fission is the same process as mitosis except because there are no organelles in prokaryotes, it occurs faster

– Examples of binary fission: bacteria and protists


Asexual Reproduction


• Examples of organisms that reproduce asexually

– Hydra – Sea Star – Strawberry

– Archaebacteria – Eubacteria

– Euglena

– Paramecium – Yeast


Asexual Reproduction


For multi-cellular organisms….

• Growth

• Repair


Where does mitosis occur?

Mitosis occurs in somatic cells

- Somatic cells are body cells or any cell besides sex cells (gametic cells or gametes:

sperm and eggs) Hint: “MY-TOE-SIS”


Do different cells divide differently?

• Different kinds of cells divide at different rates and different amounts

– Skin cells divide about every 24 hours

– Nerve cells never divide after reaching maturity (think about someone who is paralyzed)

• Every cell only has a certain number of

divisions it can go through before it dies in programmed cell death called apoptosis


What controls if cells divide?

• Mitosis is regulated by hormones in the body and in

individual cells

• There are several

“checkpoints” in the cell cycle to make

sure the cell is doing what it is suppose to be doing


What if it all goes wrong?

• Cancer is uncontrolled cell



Cell Division Control

• DNA controls all cell activities including cell division

• Some cells lose their ability to control their rate of cell

division – the DNA of these cells has become damaged or changed (mutated)

• These super-dividing cells form masses called tumors


• Benign tumors are not cancerous – these cells do not spread to other parts of the body

• Malignant tumors are cancerous – these cells break

loose and can invade and destroy healthy tissue in other parts of the body (called metastasis)


•Cancer is not just one disease, but many

diseases – over 100 different types of cancers


Practice Time…

• Work on the Cell Cycle packet, whatever you don’t finish is homework

• Complete exit ticket silently and independently

• Home learning: data and results and

conclusion sections for science fair due next class


Day 2


Bell Ringer

Which of the following phrases best describes cancer?

A. absence of cyclins in the DNA

B. multiple gene mutations on a chromosome of DNA

C. uncontrolled cell growth caused by mutations in genes that control the cell cycle

D. presence of genetic defects caused by hereditary disorders


Questions to think about…

• What must be carefully divided in Mitosis?

• What type of cells under go Mitosis?

• What moves the chromosomes in the cell?


Key Points

1. Mitosis is a part of asexual reproduction.

2. Mitosis produces 2 identical daughter cells.

3. During Mitosis, DNA is replicated and divided so each cell has an exact copy.


How is the DNA bundled for Mitosis?

Did you know! Humans have 23 pairs of chromosomes!

• Chromatid- a strand of DNA

• Chromosome: DNA condensed and “knit” together.

• Centromere: Area where chromosomes are attached

• Diploid- Having a copy of each chromosome.

How many total chromosomes do we have???


Stage 1



1. Spindle fibers form 2. Centrioles move to

opposite poles 3. Chromosomes

condense and become visible

Centrioles Spindle



Stage 2 PMAT


• Chromosomes line up along the


**** Hint: think M=Middle




What are the stages of mitosis?

Stage 3



1. Sister Chromatids

separate and move to opposite poles

**** Hint: think A= Apart For Anaphase




Stage 4 PMAT


1. Nuclear membrane reforms

2. Chromosomes unwind 3. Two daughter cells

*** Hint: think Telo= means end.


Brain Hint: TELOPHASE = TWO (touchdown!


• Cytokinesis - The cytoplasm divides and one cell

becomes two individual cells.

The process is

different in plants and animals



What are the stages of mitosis?

Stage 5

Which one is the plant cell? Which one is the animal cell?


1. What is a spindle fiber?

2. A scientist treats a cell with a toxin that destroys the spindle fibers of a mouse cell. What would happen to each phase of mitosis within the cell?







3. The phases below describe several events that occur during the process of


• (1) Attachment of double-stranded chromosomes to the spindle apparatus

• (2) Formation of single-stranded chromosomes, which are moved to opposite ends of the cell

• (3) Disintegration of the nuclear membrane

• (4) Nuclear membrane formation around each set of chromosomes, forming two nuclei

• (5) Synthesis of a spindle apparatus

What is the correct sequence of these events?


4. If a turtle’s heart cell has 20 chromosomes and the heart cell undergoes mitosis how many chromosmes would each of the

daughter cells have?

5. If cell in an oak tree’s meristem has 14 chromosomes normally. How many

chromosomes would it have during prophase?


6. Cloning in biology is the process of producing similar populations of genetically identical

individuals that occurs in nature when organisms such as bacteria, insects or plants reproduce

asexually. The term clone is derived from the

Ancient Greek word klōn, “twig”, referring to the process whereby a new plant can be created from a twig. A cloned plant has a diploid chromosome number of 12. What is the diploid chromosome number of the plant cell that was used to

produce the cloned plant?


Cancer Review

Video- ure=related&safety_mode=true&persist_safety_mode


7. What causes cancer?

8. Where in the DNA does the mutation have to occur to cause cancer?

9. What are some causes of cancer?

10. What is a cancer cell called if it is spreading throughout the body?

11. What type of cell must contain the mutation in order for it to be passed to the offspring?


Independent Practice

• Finish the Cell spinner

• Bead Lab!!!!! Follow all instructions carefully, when done, work on the lab questions

• Exit ticket to be completed silently and independently


Home Learning

• Science fair- put your board together



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