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March 16, 2017 Aims:
SWBAT explain the importance of checkpoints throughout the
Cell Cycle.
Agenda
1. Do Now
2. Class Notes
3. Guided Practice
4. Independent Practice
5. Practicing our AIMS:
C.6 – Mitotic Mistakes
How will you help our class earn all of our S.T.R.I.V.E. Points?
This is a QUICK unit!
Unit Test is in 5 days!
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MALALA YOUSAFZAI: Children’s Activist, Women’s Rights Activist (1997– )
Malala Yousafzai was born on July 12, 1997, in Mingora, Pakistan.
As a child, she became an advocate for girls' education, which resulted in the Taliban
issuing a death threat against her.
On October 9, 2012, a gunman shot Malala in the head when she was traveling home from
school.
She survived, and has continued to speak out on the importance of education.
She was nominated for a Nobel Peace Prize in 2013. In 2014, she was nominated again and
won, becoming the youngest person to receive the Nobel Peace Prize.
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OBJECTIVES: By the end of class, students will be able to…
SWBAT explain the importance of checkpoints throughout the Cell Cycle.
DO NOW
The S phase, short for synthesis phase, is a period in the cell cycle during interphase, between G1 phase
and the G2 phase. Following G1, the cell enters the S stage, when DNA synthesis or replication occurs.
At the beginning of the S stage, each chromosome is composed of one coiled DNA double helix
molecule, which is called a chromatid. At the end of this stage, each chromosome has two identical
DNA double helix molecules, and therefore is composed of two sister chromatids. During S phase, the
centrosome is also duplicated.
1. What does the S phase stand for?
2. What happens during the S phase?
3. Each chromosome originally is made of how many DNA molecules and how does this molecule
appear in the chromosome?
4. At the end of S phase each chromosome has how many coiled DNA molecules?
5. What structure holds the duplicated chromosomes together and is also copied during the S phase?
CONCEPT REVIEW
6. Forces act on the objects, initially at rest, as shown below. The magnitude and direction of the
forces are also shown. What happens to the motion of each of the objects as a result of the
forces?
SCIENCE 8 Mitosis Mistakes
C.6
Name: _____________________________
Date: ________________________________
Homeroom: _________________________
Cellular Mitosis
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CLASS NOTES
DIVIDING TO MULTIPLY All organisms are made up of cells which constantly divide and multiply.
Cells divide when:
o
o cells are replaced in our bodies every minute
Different cells divide differently:
For example
o Skin cells divide very often
o Liver cells divide rarely
o Cells in the bone marrow and lining the stomach continuously grow and divide.
When a cell dies, it breaks up and leaves an within the tissue.
This is a signal to nearby cells to start dividing in order
to fill the space.
A receptor in a nearby cell’s membrane:
o
o
o
PSST CELL!...CHECK YO’SELF! Errors during the cell cycle may lead to changes in the chromosomes
For example:
o DNA may be
o DNA may be
o DNA may be between the two daughter cells.
There are special ‘supervisors’ which make sure that everything proceeds in the
correct order during the Cell Cycle.
If something is wrong with a cell:
o
o
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☑ The 3 checkpoints ☑
Gap 1 phase – growth
Gap 2 phase – continued cell growth
Metaphase – Chromosomes line up at middle of cell
AWWW CELL!...you wrecked yo’self!
CANCER
If the ‘supervisors’ are not working properly, the cells may become
which often have altered chromosomes.
They may .
These mutated cells finally form a clump –
Errors in normally occur during , when the
chromosomes align at the middle of the cell.
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ANEUPLOIDY
If the duplicate chromosomes during
metaphase, the pair will not move properly to each pole during anaphase.
This results in one cell having two copies of the chromosome, while the other cell has
none.
This type of error is normally to the daughter cell lacking a copy
of a chromosome.
Cells receiving two copies of a chromosome will have an increase in expression of the
genes contained on the extra chromosome.
If the gene’s function is to slow growth, the extra copy may be fatal to the cell.
If the gene promotes growth, the cell may grow uncontrollably, leading to
cancer
Meet HeLa: The ongoing mitosis
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GUIDED PRACTICE
What happens when a cell dies inside our body?
How does the body know when to make new cells?
In what order does cell division occur and what ensures that nothing wrong happens?
How can a cancer tumor be formed?
Label the picture below and provide descriptions for each part of the cycle with each
label.
D: ________________
C: ________________ A: ________________
B: ________________
D
C A
B
B
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INDEPENDENT PRACTICE
1. What conditions trigger our cells to divide?
2. How many cells are replaced in our bodies every minute?
3. What signals a cell to start dividing?
4. Identify where the three checkpoints occur (during what phase) and what the cell
looks for during each checkpoint.
Checkpoint 1:
Checkpoint 2:
Checkpoint 3:
5. Why is it important for the cell cycle to be strictly controlled?
6. If cells are too damaged to be repaired, what happens to them?
7. What problem can develop if the cell cycle is not controlled?
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8. How do HeLa cells keep dividing while other cells die off?
A. HeLa ignore signals to stop dividing
B. HeLa ignore mutations that accumulate over generations
C. HeLa avoids apoptosis
D. All of the above
9. What are some of the characteristics of cancer cells like HeLa that help them evade
death?
10. Why is it so important for scientists to have a tool like HeLa cells in order to study
human disease?
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BEAST MODE: TRIMESTER THROWBACK!
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Science 8
C.6:
Mitotic Mistakes
Name: _____________________________
Date: _______________________________
Homeroom: _________________________
Quick Notes:
SKILL SNAPSHOT
Like A Scholar?
Yes No
Redo?
Yes No
Directions: Support your selection by jotting down your reasoning.
Question Reasoning
1. Sometimes, a person is born with one or more
extra chromosomes in each cell. This usually
results in abnormalities because the affected
person has
A. a reduced amount of DNA in cell nuclei
B. fewer cell mutations than a person with a
normal chromosome number
C. more DNA in each cell than a person with a
normal chromosome number
D. less DNA in cell nuclei, but more proteins in
cell mitochondria
2. During which checkpoint does the cell check
the chromosomes’ alignment?
A. G1
B. S
C. G2
D. Metaphase
3. What occurs if a cell experiences aneuploidy?
A. The cell’s damaged DNA is repaired.
B. The cell is destroyed.
C. The chromosomes do not separate equally
D. The cell will always begin growing
uncontrollably.
4. Cells divide in an organism in order to
A. grow, repair, or reproduce.
B. mutate, reproduce, or grow.
C. copy DNA, repair, or mutate
D. reproduce, copy DNA, or repair.
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5. Dr. Gey took a sample of the tumor cells from Henrietta Lacks without her or her family’s permission.
He then gave away sample of HeLa cells to labs all over the world. While Dr. Gey did not profit from
HeLa and those cells have led to countless advances in medicine, the Lacks family was completely
unaware of Henrietta’s contributions to science for decades.
Do you think what Dr. Gey did was ethical? Support your reasoning.
CONCEPT REVIEW
6. Forces act on the objects, initially at rest, as shown below. The magnitude and direction of the
forces are also shown. What happens to the motion of each of the objects as a result of the
forces?
