Unit 7 Lesson 4: Mitosis in Complex Organisms

Question 1

eukaryotes vs prokaryotes

Answer 1

Organisms that contain chromosomes within the nuclei of their cells are called eukaryotes. Organisms that lack nuclei, such as bacteria, are called prokaryotes. From bacteria to algae to zebras, cellular division happens in all living organisms.

Question 2

Can mitosis occur in prokaryotes

Answer 2

mitosis only occurs in eukaryotes, as it requires nuclei.

Question 3

Mitosis is a process in which

Answer 3

a eukaryotic cell is ‘cloned’, making genetically identical copies of it. In some single-celled eukaryotic organisms (such as certain yeasts), this is used for reproduction.

Question 4

In multicellular organisms, mitosis produces cells needed for

Answer 4

growth, development, replacement, and repair.

Question 5

1 What happens during interphase

Answer 5

During interphase, a parent cell copies itself, and during mitosis the copies are separated into two identical daughter cells.

Question 6

2 What happens during prophase

Answer 6

In prophase, the cell begins to prepare for replication by condensing its chromosomes. The nuclear membrane dissolves and the mitotic spindle, which will help organize the chromosomes, is formed. Microtubules from the spindle capture and organize each chromosome.

Question 7

3 What happens during metaphase

Answer 7

During metaphase, the spindle lines up the captured chromosomes. It checks that the microtubules are correctly attached so the chromosomes will divide correctly.

Question 8

4 What happens during anaphase

Answer 8

In anaphase, microtubules pull the replicating chromosomes apart, separating them into sister chromatids. The pairs of new chromosomes then begin to move away from one another to opposite sides of the cell.

Question 9

5 What happens during telophase

Answer 9

During telophase, each pair of sister chromatids finishes moving to opposite sides of the cell. Two new nuclei (one for each set of chromosomes) are formed.

Question 10

6 What happens during cytokensis

Answer 10

Cytokinesis can begin during anaphase or telophase. It is the physical process of cell division. During cytokinesis, the cytoplasm of the cell divides and separates, forming two new cells.

Question 11

Complex organisms grow through the process of cellular division. Elaborate

Answer 11

One cell divides to become two, and then the process repeats itself creating more and more cells as the organism’s tissues and organs increase in size.

Question 12

When cells reproduce by mitotic division, they are

Answer 12

proliferating

Question 13

Proliferation in the cell cycle simply means

Answer 13

growth, but growing organisms do not only add identical cells to become larger. Their cells must also undergo differentiation. Differentiation is the process by which cells become more specialized to fulfill different functions.

Question 14

Differentiation is the process by which cells become

Answer 14

more specialized to fulfill different functions.

Question 15

In eukaryotes (such as the zebra), development is a process that happens alongside

Answer 15

growth, transforming the organism as it grows larger.

Question 16

For complex animals like zebra were does development start

Answer 16

Development starts in the womb.

Question 17

A baby zebra, like all baby mammals, begins life as a single cell called a

Answer 17

zygote

Question 18

What happens to a zygote

Answer 18

That single cell undergoes mitosis to become more cells.

Question 19

How does a zygote become a blastocyst

Answer 19

Those cells rapidly proliferate until the zygote has grown into a blob of cells called a blastocyst.

Question 20

blastocost vs zygote

Answer 20

The blastocyst is much larger than the zygote from which it came, but it is still just a blob.

Question 21

How does this blastocyst become a zebra?

Answer 21

The zebra zygote is a stem cell. Stem cells are unspecialized cells that may differentiate into more specialized cell types. A stem cell’s ability to differentiate depends on its cell type.

Question 22

What are Totipotent cells

Answer 22

Totipotent cells are the first stem cells to arise in a developing embryo. These cells are able to differentiate into any cell type the growing embryo needs and may also become extraembryonic cells. These are located outside the embryo. They can also be called extraembryonic placental cells.

Question 23

What are pluripotent cells

Answer 23

Pluripotent cells are the second type of stem cell to develop in an embryo. A pluripotent cell can differentiate into any cell type within the body but cannot become extraembryonic.

Question 24

What are Multipotent stem cells

Answer 24

Multipotent stem cells make up most adult stem cells (also called somatic cells). A multipotent stem cell can become many different types of specialized cells within a tissue or organ but is more limited than a pluripotent cell. In some parts of the body, such as the intestinal tract, multipotent stem cells divide regularly to repair aged or damaged tissues.

Question 25

What kind of cell is a zyogote

Answer 25

The zebra zygote is a totipotent stem cell

Question 26

The zebra zygote is a totipotent stem cell. What tranformaitons does the stem cell go through

Answer 26

During its first divisions, the cells it creates become pluripotent stem cells. Those cells then differentiate into the different types of cells that will make up the tissues and organs of a baby zebra.

Question 27

The chromosomes of every cell contain deoxyribonucleic acid, or DNA. DNA strands are like a cellular recipe book.

Answer 27

They contain instructions for everything the organism needs to grow and develop. Each job a cell might do is coded onto part of its DNA strand.

Question 28

The process in which a cell differentiates by reading a specific section of DNA code is called

Answer 28

gene expression.

Question 29

gene expression

Answer 29

the process in which instructions in DNA are used to produce a protein or other functional product

Question 30

Not every cell does the same job, of course. How

Answer 30

In gene expression, the cell creates a copy of a particular piece of its own DNA, like making a copy of a recipe from a recipe book. This copy will be read by the cell’s ribosomes which will then form the proteins it needs to carry out the specific function called for by that DNA segment, like making the recipe.

Question 31

During differentiation the stem cells process different sections of DNA into products, like using different recipes in the book. What does this allow them to do

Answer 31

This allows them to become specialized in order to carry out specific functions. By turning on or off the parts of the DNA script that are read, stem cells produce different proteins which allow the cells to specialize.

Question 32

What determines the type of differentiation of a stem cell?

Answer 32

In a complex organism such as the zebra, gene expression is determined by outside environmental factors, by the types of nearby cells, by chemical signals within the organism, or by a combination of all three.

Question 33

. A cell’s particular developmental program for specialization is called its

Answer 33

cell fate.

Question 34

Depending on its cell fate, each stem cell differentiates into different cell types;

Answer 34

such as a bone cell, a blood cell, an epithelial cell, a fat cell, a muscle cell, a nerve cell, an immune cell, or a sex cell. Each of these cell types has a specific function

Question 35

Once cells are differentiated, they can continue to

Answer 35

proliferate and grow

Question 36

Once an organism reaches adulthood, is mitois needed

Answer 36

it no longer needs mitosis to grow and develop.

Question 37

In complex organisms such as the zebra, cells are constantly growing senescent and dying. What does that mean

Answer 37

A senescent cell is one that can no longer reproduce itself and, of course, a dead cell cannot fulfill its function.

Question 38

Life span of red blood cells vs human bone cells

Answer 38

Red blood cells, for instance, live about four months, while some human bone cells can live up to 25 years. However long they live, worn out and dying cells are replaced by mitosis.

Question 39

In addition, cells in a complex organism can often become damaged.

Answer 39

If the adult zebra strains a muscle while splashing up a riverbank, the torn tissues must be repaired. When an organism is wounded or injured, cells respond by rushing to the damaged area and proliferating to replace injured tissue or lost blood. Some organisms, such as starfish and flatworms, use mitosis in this way to replace entire missing body parts.

Question 40

How is the function of mitosis different in an adult animal than in a baby?

Answer 40

Adult animals need mitosis only for repair and replacement, while babies also use it for growth and development.

Question 41

Why does differentiation take place?

Answer 41

Differentiation allows an organism to develop, replace, or repair cells.

Question 42

What can determine a stem cell’s differentiation?

Answer 42

the environment, nearby cells, chemical in the body, or a combination of all three

Question 43

What is the process by which identical daughter cells become more specialized?

Answer 43

The process of specialization is called differentiation.

Question 43

Explain the life cycle of a skin cell that starts at the site of a skinned knee. Start with the parent cell and end with the skin cell healing the scrape.

Answer 43

The first thing that happens is mitosis, where one parent cell produces two daughter cells that are stem cells. The environmental factor is a skinned knee, and the nearby cells are skin cells, so through differentiation the cell will change from a stem cell to a skin cell. The cell will move to the site of the skinned knee and start the healing process.

Question 44

When burn victims need a skin graft, what do doctors do

Answer 44

doctors will take healthy skin from an undamaged part of the victim’s body and transplanted to the burn site. The process is painful, uncertain, and can take weeks to complete.

Question 44

what do burns do to the skin

Answer 44

Burn injuries can be very risky and difficult to treat. It is important that severe burns be treated as quickly and efficiently as possible in order to reduce the risk of life-threatening complications. Since burns destroy the skin, leaving the body open to bacterial invasion, burn victims run a high risk of infection. To reduce the risk of infection, bandages need to be removed and wounds cleaned regularly.

Question 45

Because new skin cannot form quickly over severe burns, a common treatment called a

Answer 45

skin graft is used.

Question 46

what happen during skin graft surgery

Answer 46

In a skin graft surgery, a healthy piece of skin is transplanted over the damaged area of the patient’s body. In

Question 47

What happens in n a successful skin graft

Answer 47

In a successful skin graft, the patient’s body treats the graft as though it belongs at the site and heals the injury. New blood vessels are generated by the patient’s body, giving the graft a blood supply and ultimately incorporating the new skin into the patient’s body.

Question 48

Recently doctors have developed two different techniques that use stem cell technology to produce the skin needed for grafts. Whats the first technique

Answer 48

In the first technique, stem cells are harvested from the patient’s bone marrow, encouraged to differentiate as skin cells, and grown in a laboratory. When enough cells have proliferated, the new skin is transplanted back to the patient. Growing enough new skin cells to treat a burn takes about three weeks.

Question 49

Recently doctors have developed two different techniques that use stem cell technology to produce the skin needed for grafts. What is the second technique

Answer 49

In the second technique, embryonic stem cells are taken from umbilical cord blood which is donated by hospitals after a baby is born. The embryonic cells are also encouraged to differentiate as skin cells and then grown in a lab. The growth process for embryonic cells takes about the same amount of time as the process for cells harvested from adult bone marrow.

Question 50

Because transplanted skin is foreign to the burn victim’s body, it can be difficult for the patient’s body to incorporate and typically leaves the patient with a lot of scarring. However, grafts performed using cultured cells typically leave less scar tissue than skin grafts performed by traditional methods. What could cause this difference?

Answer 50

In addition to the lowered risks of infection and rejection, skin cells that finish differentiating after transplant can answer environmental signals more effectively. This allows them to incorporate more completely into the healing wound, resulting in less scarring.