Download Asexual vs. Sexual Reproduction

Life Science A
Unit 2
Answer Key:
Asexual vs. Sexual
Reproduction
Name _________________________________________
Date____________________________
Objective
In this activity, you will observe and describe the variations in reproductive patterns of
organisms, including asexual and sexual reproduction.
Activity
There are two principal modes of reproduction, asexual and sexual. Asexual reproduction requires
one parent. Forms of asexual reproduction include binary fission, budding, and fragmentation. Sexual
reproduction requires two parents. There are advantages and disadvantages to each form of
reproduction.
Asexual means “without sex” in the Greek language. Asexual reproduction uses mitosis to create
a new individual in which all of its genes come from one parent without the fusion of sperm and egg.
Some organisms that use asexual reproduction include bacteria, hydra, and starfish.
A bacterium consists of circular DNA and proteins. In binary fission, a bacterium goes through
these steps:
1. Replication of its chromosomes (DNA).
2. A copy of chromosomes moves to one end of the cell; the original chromosomes move to the
other end.
3. The plasma membrane grows inward; the cell wall deposits itself.
4. Two daughter cells results.
A hydra is a multi-cellular organism that reproduces by budding. Budding is a mitotic process in which
the parent produces a mass or a bud of cells. This bud of cells is an exact copy or clone of the parent.
Eventually the bud separates from the parent and forms a new hydra.
A starfish reproduces by fragmentation. In the fragmentation process, the starfish body is broken into
several pieces. Some or all of these pieces will develop into a new organism. Fragmentation must be
accompanied by regeneration. Regeneration is not asexual reproduction. It is the regrowth of body
parts that have been lost.
Sexual reproduction is the creation of offspring(s) by the union of a female gamete (ovum) and a male
gamete (spermatozoon). These two haploid cells fuse together to form a zygote. Haploid means that
it has “half” of the normal amount of chromosomes for that species. Humans have 46 chromosomes.
A female gamete has 23 chromosomes, and a male gamete has 23 chromosomes. Most multi-cellular
organisms use sexual reproduction to create offspring.
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There are some potential advantages for each type of reproduction. These advantages may be
specific to organisms. They may ensure the longevity of a species. On the other hand, they could
mean the demise of a species.
Asexual reproduction has several advantages. It can produce numerous offspring in a short time.
If an organism lives in an isolated place, it can still reproduce without a mate. The offspring is an
identical copy of the parent, which could be beneficial.
Sexual reproduction has several advantages that we see every day. Sexual reproduction gives rise to
offspring that have a combination of both parents, thus more variety. By combining genetic material
from both parents, there is a chance to minimize or avoid the genes for deadly disorders from one
parent. This genetic variation occurs mainly during meiosis and fertilization.
1. Place a check under the correct form of reproduction.
Feature
One parent
Two parents
Bacteria
Humans
Starfish
Cats
Hydra
Dogs
Asexual
9
Sexual
9
9
9
9
9
9
9
2. What are the three forms of asexual reproduction mentioned? What form of reproduction
requires the assistance of regeneration?
Binary fission, budding, and fragmentation. Fragmentation requires the process of
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regeneration to create a new organism.
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3. List the advantages for each form of reproduction.
Asexual:
1.
no need for a mate
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2.____________________________________________________________________________
produce numerous offspring in a short time
3.____________________________________________________________________________
a clone of a parent
Sexual:
1.____________________________________________________________________________
provides a diverse offspring
2.____________________________________________________________________________
can mask or hide deadly genes
4. In this exercise, you will create an original organism by budding. In the first box, draw an
imaginary organism about the size of a quarter, this is the parent. Draw the exact same
organism but much smaller, and it must be attached to the parent organism. This smaller
version is the offspring that is budding. In the second box, draw the parent and the offspring
unattached. You have created an offspring by budding.
Parent with offspring attached
Parent and offspring unattached
Images will vary. The first image should be
a parent with the offspring attached.
The second image should be the parent
and the offspring unattached.
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Life Science A
Unit 2
Answer Key:
Sickle Cell Anemia
Name _________________________________________
Date____________________________
Objective
In this activity, you will learn the importance of iron in red blood cells and how free iron may
cause organ damage, especially for those who suffer from sickle cell anemia.
Activities
Oxygen is necessary for human life. With each breath, oxygen is exchanged for carbon dioxide in our
lungs. The oxygen attaches to our red blood cells and is carried throughout the body. Hemoglobin is
the component in red blood cells that carries oxygen. Oxygen attaches to iron found in hemoglobin.
The prefix “heme” means iron, and the presence of oxygen and iron gives our blood cells their red
color. Without iron, oxygen could not be transported through the body. Individuals with low amounts
of iron attached to their red blood cells are referred to as anemic.
Anemia may be caused by many different factors. Sickle cell anemia is an inherited blood disease
that is characterized by defective hemoglobin. Red blood cells sickle because of a genetic defect that
occurs in individuals with this disease. It is caused by a genetic mutation in the coding of an amino
acid needed to form healthy blood cells.
There are several interesting facts about sickle cell anemia. First, sickle cell anemia only affects
individuals that live in or are descendants of equatorial countries; second, individuals with sickle cell
or who carry the trait cannot contract malaria. (The amino acid that is mutated is the site malaria
needs to infest human blood.) Finally, the mosquitoes that carry malaria (a disease caused by
parasites that affects red blood cells) are only found in equatorial regions. Individuals develop sickle
cell when the trait is passed to them by both parents. If only one parent passes the trait, the person is
considered a carrier. A carrier does not have sickle cell but could pass it to his or her children.
Normal red blood cells are round and smooth. They are designed to move easily through blood
vessels. When red blood cells become shaped like a sickle or scythe, they become stiff. These cells
cannot move as easily through the blood stream. Because of the odd shape of the cells, they tend to
clump and clog the blood vessels. When this occurs, the blood that is carrying oxygen cannot reach
its destination.
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Normal blood cells
Normal red blood cells and a sickled cell
When cells sickle, blocking blood vessels and causing anemia, the individual suffering with the
condition is said to be in crisis. After several crises, red blood cells decrease their ability to carry
oxygen. The spleen (an organ responsible for blood storage and the destruction of old blood cells)
may shut down in a severe crisis. A sickle crisis causes extreme pain, swelling of the toes and
fingers, and possible death of the tissue where oxygen could not reach. One extremely dangerous
effect of sickle cell anemia is pooling. Pooling is when the sickle cells pool, or collect, in the spleen.
This causes a sudden drop in the hemoglobin.
When a cell sickles, it also loses iron. Although iron is needed within hemoglobin to transport oxygen,
large amounts of free iron (not attached to the hemoglobin) is poisonous to the body and may
damage internal organs. The same iron needed to carry life-giving oxygen can cause organ damage
and lead to death if the amount is out of balance with what the body needs.
It is suggested that sickle cell patients take vitamins rich in folic acid to recover from a crisis quickly.
Folic acid helps the body produce red blood cells at a faster rate. Some researchers believe that
children with sickle cell need about 20% more calories than other children. This increase in calories is
needed to fuel the production of red blood cells and to replace the damaged, sickled cells.
1. What group of people tends to have the trait for or carry sickle cell anemia?
People
who live in or who are descendants of equatorial regions.
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2. What can a person with sickle cell do to recover from a crisis quickly?
Take vitamins that are rich in folic acid.
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3. Why do sickled red blood cells cause so many problems?
Sickled red blood cells get stuck and clump in the blood vessels. When this occurs, there is pain,
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swelling, anemia, and possible pooling. The red blood cells can not deliver oxygen to the body.
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The cells can also release iron, causing the organs to receive heavy metal poisoning.
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4. If a child receives the gene mutation that causes sickle cell from one parent, will the child have the
disease? What if the mutation is received from both parents?
No. If the child receives the trait from one parent, the child will be referred to as a carrier, or
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someone who can pass on the disease. If both parents pass the trait on to the child, the child will
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have sickle cell anemia.
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Life Science A
Unit 2
Answer Key:
Life Is in the Blood
Name _________________________________________
Date____________________________
Objective
In this activity, you will learn about the importance of blood donation.
Link
American Red Cross
http://www.pleasegiveblood.org/education/about_blood.php
Activities
Blood donations save millions of lives each year. Giving blood is a simple way to save the life of
someone in your community.
Access http://www.pleasegiveblood.org/education/about_blood.php and read the following
sections: All About Blood, Blood Types; How Blood is Tested, How Blood is Processed, and FAQs
to find out about the different products that are made from blood, how all human blood is alike and
different, how blood is processed, and much more.
1. What are the two most common blood types in the United States?
a. O-positive and B-positive
b. O-negative and A-positive
c. O-positive and A-positive
d. B-positive and A-negative
2. What are the four components that can be derived from a unit of blood?
a. AHF, white blood cells, red blood cells, and hemoglobin
b. AHF, platelets, red blood cells, and hemoglobin
c. platelets, white blood cells, albumin, and plasma
d. red blood cells, platelets, AHF, and plasma
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3. Where are red blood cells manufactured?
a. in the heart
b. in the spleen
c. in bone marrow
d. in joints
4. Is it possible to contract HIV by donating blood? Explain your answer.
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No. HIV and other transmissible viruses cannot be contracted through blood donation. The
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equipment used is sterile and used only once then immediately discarded, and a new needle is
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used for each donation.
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5.
What is a Universal Donor? Explain why.
A person who has type O blood is a universal donor because his or her red blood cells may be
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transfused to patients of any other blood type in an emergency situation or if the needed blood
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type is unavailable.
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Life Science A
Unit 2
Answer Key:
Feedback Mechanisms
Name _________________________________________
Date____________________________
Objective
In this activity, you will learn about feedback mechanisms with a system that serves to keep
changes within a specified limit.
Activities
Human beings are complex organisms. There are millions of functions that are occurring
simultaneously inside the human body. Many of these functions are self-regulating. In a selfregulating process, the product of the process regulates the process. One of the most important
processes is to maintain stability, homeostasis, in an ever-changing external environment. The
human body carries out this regulatory process through feedback mechanisms. Some of the functions
of feedback include regulating cellular respiration, body temperature, chemical reactions, and blood
clotting. Feedback mechanisms are considered positive or negative.
Positive feedback speeds up or amplifies a change in the human body. One example of positive
feedback is human blood clotting. The blood vessels become injured, and the platelets release
chemicals. These chemicals attract more platelets, and they begin to clump together. Eventually, the
platelets stick together to seal the wound. Positive feedback is less common than negative feedback
in the human body.
Negative feedback slows down or stops a process. This mechanism prevents small changes from
becoming too large. One negative feedback mechanism is cellular respiration. It is the most common
way for a cell to make energy or ATP. Cellular respiration consists of an anabolic pathway (electron
transport chain) and a catabolic pathway (glycolysis and Kreb cycle). During the anabolic pathway,
complex molecules are synthesized, or made from, simpler molecules. During the catabolic pathway,
complex molecules are broken down, and energy is released.
Cellular respiration involves glycolysis, the Kreb cycle, and the electron transport chain. Glycolysis
takes place in the cytosol of the cell and begins the breakdown of glucose (sugar). The Kreb cycle,
which takes place in the mitochondrial matrix, finishes the job by breaking down pyruvate into carbon
dioxide. The carbon dioxide represents remnants of organic molecules. The third step, the electron
transport chain, uses electrons from the Kreb cycle and combines them with hydrogen and oxygen to
make water.
Certain enzymes set the pace for cellular respiration. They contain receptor sites that are specific for
inhibitors or activators. For example, if there is an abundance of ATP, the cell slows down making a
certain enzyme used in glycolysis. Once ATP is low, the cell will activate the enzyme and speed up
glycolysis.
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If you are exercising, there is a need for more energy in the muscle cells. The cells that do not need
energy immediately will slow down or stop making ATP. The enzymes will start, stop, or slow down
cellular respiration at different steps in the process.
To sum it up, glycolysis changes glucose to pyruvate and produces a little energy, ATP. The Kreb
cycle takes the pyruvate and combines it with another compound to form electrons the electron
transport chain can use. The Kreb cycle produces a little energy and some electrons. The electron
transport chain makes the bulk of the energy for cells.
1. What are the two types of feedback mechanisms, and how do they differ?
Positive feedback speeds up or amplifies a change in the human body. Negative feedback
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slows down or stops a process.
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2. Thermoregulation is the body’s ability to regulate its internal temperature. As a human, your
optimal internal temperature is 98.6° F. Imagine going outside, and it is 105° F. You are
dressed in a heavy coat, boots, snow pants, gloves, and a hat. This clothing is going to
increase your internal body temperature. What are some of the symptoms that your body is
trying to regulate itself when it is extremely hot outside? How can you help your body cool
down even faster?
Your body wants and needs to cool down internally. It will sweat and breathe harder to cool
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down. You can remove the excess clothing to quickly lower the stress on the body.
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3. Positive feedback is not as common as negative feedback in humans. What is the example of
positive feedback from the passage above? Why is this example so important to humans?
One example of positive feedback is the human blood clotting. The blood vessels become
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injured, and the platelets release chemicals. These chemicals attract more platelets, and they
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begin to clump together. Eventually, the platelets stick together to seal the wound. It is
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important that this function happens fast. If not, a person could go into shock or bleed to death.
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4. What are the three parts of cellular respiration? How much energy does each component
make?
The three parts of cellular respiration are glycolysis, Kreb cycle, and electron transport chain.
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Glycolysis makes a little energy. The Kreb cycle makes a little energy for cells. The electron
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transport chain makes the bulk of the energy for the cells, thus for the entire body.
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Life Science A
Unit 2
Answer Key:
Growing Hair
Name _________________________________________
Date____________________________
Objective
In this activity, you will illustrate how hair grows too slowly to be observed with the naked eye.
Activity
Read the passage below. Then, answer the questions that follow.
Some processes happen too slowly on too small of a scale to be observed by the naked eye. We
know that they are occurring, but how can it be proven? Let’s discuss human hair. We know that it
grows naturally. This growth can be measured by the length and diameter of the hair. We know that
we shed hair. We have hair on our heads, and we have hair on our bodies, which is called body hair.
Although body hair and hair on your head grow to different lengths, they go through the same growth
process. Hair has a life cycle. This life cycle has three phases—active, transitional, and resting.
During the active, or anagen, phase, there is protein synthesis and hair growth. During the transitional
phase, the hair growth slows down until it stops. This takes about two weeks. The last phase is the
resting, or telogen, phase. The old hair comes out of the hair follicle, and the new hair replaces it.
Body hair and hair on the head grow at different rates. Body hair grows less than 1/3 of a millimeter
per day. Hair on your head grows approximately 1/2 of a millimeter per day. Here is what we know:
•
•
•
•
•
Hair grows fastest in the summer.
Hair grows slowest in the winter.
Hair growth is the best between the ages of 15 and 30.
Hair growth slows down between the ages of 40 and 50.
Adults begin to lose hair around the age of 50.
If scientists know that hair grows although we can not see it, how is it measured? Scientists use
optical microscopy and image analysis to measure hair growth. Optical microscopy is the use of a
specialized microscope attached to computers. The hair is removed from the scalp and placed on a
glass slide to be viewed on the microscope. Digital image analysis is the use of computer software to
view the image of the hair follicle from the microscope. The digital imaging software can also measure
the hair. By combining these two things, scientists are able to accurately measure hair growth and, in
particular, hair length. The hair diameter, or thickness, is negligible, making it nearly impossible to
measure.
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Based on this information, answer the following questions.
1. You have been asked to volunteer in a clinical trial for a hair growth product. It is hypothesized
that your hair will grow two centimeters per day. First you must shave your head, and then
apply the hair product to your scalp. You set the timer and wait 24 hours. After 24 hours, you
shave your head again and place a strand of hair on a glass slide. What should you do next?
Put the glass slide under a microscope and look at it. Save the image on the computer.
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Measure its length to see if it is two centimeters.
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2. On average, how fast does hair grow?
Hair
on one’s head grows about 1/2 mm per day. Body hair grows approximately a 1/3 of a
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millimeter
a day.
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3. What are the three phases of hair growth?
The three phases are active (anagen), transitional, and resting (telogen).
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4. When does hair grow the fastest and the slowest?
Hair grows the fastest in the summer and the slowest in the winter.
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5. The longest hair known to be grown by a human is 5.6 meters. Knowing this, how many days
do you think it took for the hair to grow that long? Here is a hint: Hair grows 1/2 millimeter per
day, which equals 0.0005 m.
5.6 meters ÷ 0.0005 meters per day = 11,200 days
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Life Science A
Unit 2
Answer Key:
Effects of Drugs
on Enzymes
Name _________________________________________
Date____________________________
Objective
In this activity, you will describe how factors such as radiation, ultraviolet light, and drugs can
alter cellular structure or function.
Activity
Most chemical reactions in the body can be described using the lock and key theory. This theory
states that a substrate, or substance that needs to be changed, has the same shape of the
enzyme (lock) and fits within the active site of the enzyme like a key. Functions, including those
that occur on the cellular level, are regulated by the body using this type of mechanism.
Although cellular functions are regulated by the body, in most cases they can be changed by external
factors. These factors include radiation, ultraviolet light, and the use of drugs. The focus of this
activity is the effect of drugs on the active sites of enzymes.
Enzymes are proteins that catalyze, or speed up, chemical reactions. Reactions are increased by
lowering the activation energy. In some cases, reactions need to be hindered, especially those that
are caused by cells that reproduce uncontrollably. When cells reproduce at an uncontrollable rate, the
term used to describe those cells is cancer. In other cases, the use of drugs can block or inhibit the
active site of a reaction.
Enzymes are not altered in a chemical reaction, so they can be reused repeatedly.
An example of the lock and key theory is shown below. The enzyme has an active site where the
substrate (reactants) bonds. The enzyme may adapt to improve the fit with the substrate. The
enzyme forms a bond with the product. Eventually, the products are formed, and the enzyme returns
to its original form.
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When an active site is blocked directly by another substance and the reaction does not occur, it is
called competitive inhibition. When a site other than the active site is filled with an inhibitor and the
reaction can not take place, it is called noncompetitive inhibition. Many drugs block the natural
reactions that occur in the body either by causing another reaction to occur (competitive inhibition)
or just by blocking the active site (inhibition) and not allowing any reaction to occur.
Many drugs target enzymes at signaling points. From the table below, you can see the purpose
and possible side effects of several classes of drugs.
Drug type
Example
Purpose/ Function
Side Effect(s)
Psycho
stimulants
Amphetamine
Increase awareness and
arouse pleasure centers
Dizziness, blurred
vision, addiction
Opiates
Morphine
Suppress response to
pain
Can become
addictive as well as
suppress vital body
functions (ex. heart)
Nicotine
Tobacco
Mild stimulant
Addictive and may
cause cancer
All of these drugs affect the targeted enzyme at the active site or the inhibitor site, depending on
whether it is competitive or noncompetitive. The drugs block the site, and other reactions that
need to occur within the body are blocked. This interference can cause permanent damage within
the cells and the entire body.
Use this information to answer the following questions.
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1. Name three things that can alter cellular function.
radiation,
ultraviolet light, and drugs
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2. How does an enzyme affect a chemical reaction?
An
enzyme speeds up a chemical reaction by lowering its activation energy.
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3. What are some of the side effects from using drugs that interfere with cellular function? Use
the table provided.
drug addiction, blurred vision, cancer, heart failure, etc.
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4. Match the following terms.
d
______
enzyme
a. an inhibitor attaches to the active site
e
______
active site
b. a reactant
b
______
substrate
c. an inhibitor attaches to a site other than
the active site
d. a protein that speeds up a reaction
f
______
opiate
a
______
competitive
e. location where the substrate attaches to
the enzyme
c
______
noncompetitive
f. a drug that suppresses response to pain
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Life Science A
Unit 2
Answer Key:
Cell Division
Name _________________________________________
Date____________________________
Objective
In this activity, you will learn about prokaryotic and eukaryotic cell division.
Link
Cell Division: Binary Fission and Mitosis
http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookmito.html
Mitosis
http://www.contexo.info/DNA_Basics/Mitosis.htm
Activity
The cell is the basic unit of life. All living cells can be divided into two groups: prokaryotic and
eukaryotic. Animals, plants, fungi, protozoans, and algae all possess eukaryotic cell types. Only
bacteria have prokaryotic cell types.
Access http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookmito.html to learn about how
prokaryotic and eukaryotic divide and then answer the questions that follow.
1. What features do prokaryotic and eukaryotic cells have in common in their cell division process?
Replication of the DNA in both prokaryotic and eukaryotic cells must occur. The cell is first
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segregated and then replicated. Cytokinesis, the process where one cell splits off from its sister
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cell, ends this cell division process.
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2. How are prokaryotic and eukaryotic cells different?
Prokaryotic
cells are much simpler in their organization than eukaryotic cells. They also have
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many
more organelles and chromosomes.
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Copyright © 2006 PLATO Learning, Inc. All rights reserved. PLATO® is a registered trademark of PLATO Learning, Inc. Straight Curve, Academic Systems, and PLATO Learning are
trademarks of PLATO Learning, Inc. PLATO, Inc. is a PLATO Learning, Inc. company.
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3. What is the usual method of prokaryotic cell division called?
binary
fission
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4. Define binary fission.
Binary fission is the method by which a cell reproduces. It is a form of asexual reproduction in
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which a cell divides into two “sister” cells after DNA replication.
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5. Briefly describe how prokaryotic cells divide.
The prokaryotic cell first replicates, and then it attaches the new copy to a different part of the cell
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membrane. When the cell begins to pull apart, the replicated cell and original cell are separated.
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After this process, there are two cells of identical genetic composition.
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6. During mitosis, if the parent cell has 46 chromosomes, then the daughter cell should end up with
46 chromosomes.
_____
Access http://www.contexo.info/DNA_Basics/Mitosis.htm to learn about the different phases of cell
division during mitosis and then answer the questions that follow.
7. In which stage of mitosis do all of the chromosomes line up across the center of the cell?
metaphase
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8. In which phase do the chromosomes coil and become short and thick?
prophase
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9. In which phase do the chromosomes separate?
anaphase
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10. In which phase does a new nuclear membrane form in each daughter cell?
telophase
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Copyright © 2006 PLATO Learning, Inc. All rights reserved. PLATO® is a registered trademark of PLATO Learning, Inc. Straight Curve, Academic Systems, and PLATO Learning are
trademarks of PLATO Learning, Inc. PLATO, Inc. is a PLATO Learning, Inc. company.
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