BioA: Cells- Stability and Change

The sequence of events in the cell cycle

1. G1 phase: organelles are copied, and the cell grows. 2. S phase: DNA is replicated to make two copies. 3. G2 phase: additional growth occurs before the cell divides. 4. M phase: mitosis occurs, and one cell divides into two.

Give a specific situation in which an organism's cells would need to divide.

1. A tissue needs repairing 2. More cells are needed to defend the body

The steps of the changes that occur in the organization of the chromosome as the cell progresses into mitosis.

1. DNA is wrapped around histones at regular intervals, forming chromatin. 2. Interactions between parts of histones compact the DNA. 3. The chromosome coils more and more tightly, forming supercoiled DNA. 4. Condensed, replicated chromosomes attach at a pinched region called the centromere.

Which segment has more stem cells present in a planarian and why? The mid-section with eyespots 4 days after being cut? The tail end with eyespots 2 days after being cut?

?

Why do your skin cells divide more frequently than a liver cell?

A liver cell normally remains in G0, and it doesn't grow or regenerate.

How is a proto-oncogene different from an oncogene?

A proto-oncogene is a normal cell with regulated cell growth. An oncogene accelerates cell growth and division (cancer cells).

One half of a duplicated chromosome is called a

Chromatid

List the major characteristics of Telophase (how do you identify it?) Sketch the telophase cell

Chromatids are at opposite poles, there is a nuclear membrane, and the cell starts to separate

List the major characteristics of Anaphase (how do you identify it?) Sketch the anaphase cell...3 chromosomes still

Chromatids separate

Your body cells have 46 long threads of DNA that consists of many genes...these are

Chromosomes

List the major characteristic of Metaphase (how do you identify it?) Sketch the same 3 chromosome cell in metaphase

Chromosomes are in the middle

Cells that carry out everyday functions but do not undergo the processes to prepare for division are where in the cell cycle?

G0

Which is the correct order of the cell cycle?

G1, S, G2, Mitosis

How are genes in DNA involved in the differentiation and specialization of cells? What is the difference between an expressed gene and a gene that is not expressed?

Genes and DNA are involved by switching on or off to send instructions to make stem cells, or specific types of cells. An expressed gene is used to make proteins that carries out a specific function within the cell. Meanwhile, genes that aren't expressed are used to make other cell types and not proteins.

What is an example of external factors at work to regulate cell division?

Growth factors, such as receptors for cell to cell contact, or release of chemical signals to stimulate other cells.

The following occurs during a eukaryotic cell's life cycle. When exactly?

Growth: Gap1 and Gap2 (Interphase) Normal metabolism: Gap1 (Interphase) DNA replication: S (Interphase) Division: M (Mitosis and cytokinesis)

No matter how materials move across the membrane, they must be transported in adequate amounts and with adequate speed to

Maintain homeostasis

Which of these statements best explains how advancements in technology influenced the development of the cell theory?

Microscopes enabled scientists to see cells.

_ refers to a stem cell's ability to differentiate into other cell types

Potency

Which types of cells do not undergo mitosis?

Sex cells

Which type of reproduction produces genetically unique offspring?

Sexual reproduction

Telomeres are strings of repeating nucleotides that provide a "cap" on the ends of chromosomes. Though telomere sequences do not contain genes, why might they be important during an organism's life span?

Telomeres prevent loss of genes when chromosomes are replicated.

How are rates of cell division in normal cells different from rates of cell division in cancer cells?

The rates of division and normal cells are controlled and normal, while cancer cells have uncontrolled and abnormal growth rates.

What happens to the surface area to volume ratio as a cell gets larger?

The ratio (SA:V) decreases

What would happen if mitosis took place in a cell but cytokinesis did not?

The result would be a single large cell with two nuclei, each containing a full set of chromosomes.

Different factors regulate cell growth and division. Cells are limited in size because they need a large *surface area* as compared to their *volume.* This ensures that materials can move into and out of the cell at adequate rates. The cell cycle is also regulated by external factors such as *growth factors* and internal factors such as *cyclins.* These factors work together to make sure the cell enters the appropriate phase of the cell cycle at the correct time.

The size of cells are limited by the ratio of surface area to volume. The cell cycle is regulated by external growth factors and internal cyclins.

In adults, the liver does not normally grow larger or regenerate cells. Based on this knowledge, most adult liver cells would be expected to:

be in the interphase, or resting, phase.

The difference in DNA between liver cells and heart cells is...

gene regulation

Where is DNA located in eukaryotic cells?

inside the nucleus

Human cells have 46 chromosomes. How many chromosomes should be present in each daughter cell after mitosis?

46

What types of cells are produced during cell differentiation?

A cell with a specific shape and function

What is a chromosome? How many chromosomes do you have in your body cells? What does diploid mean?

A chromosome is one long continuous thread that consists of many genes. Humans have 46 chromosomes in their body cells. Diploid means two sets of chromosomes (46).

What is prophase?

A stage in mitosis where DNA and histones condense, and nucleus begins to break down.

What is anaphase?

A stage in mitosis where chromatids separate and move to opposite sides of the cell.

What is metaphase?

A stage in mitosis where chromosomes line up along the cell equator; spindle fibers attach to each chromosome.

What is telophase?

A stage in mitosis where the nuclear membrane reforms and chromosomes uncoil.

totipotent stem cells

A stem cell can give rise to all cell types

In which of these scenarios would the rate of mitosis most likely increase?

A tissue is damaged and requires repair, a person has a "growth spurt" and grows taller, and a tissue loses a large number of cells due to wear and tear.

In which of these situations would cells most likely receive signals instructing them to enter the M phase of the cell cycle? Select all correct answers.

A tissue needs repairing, and more cells are needed to defend the body.

Which of these is not a principle of cell theory?

All organisms are made up of many cells.

Programmed cell death occurs when cells produce self-destructive enzymes, this is called

Apoptosis

Use the terms below to complete this statement explaining how mitosis produces two genetically identical cells. During interphase, DNA is in a loosely arranged form called *chromatin.* Before a cell divides, each chromosome is duplicated so that each daughter cell will have a complete set of DNA. As a cell progresses into prophase, the cell's DNA condenses to form tightly coiled chromosomes. In addition, the *nuclear membrane* breaks down, and centrioles begin to move to opposite poles of the cell. In metaphase, chromosomes align along the cell equator, and *spindle fibers* attach to each chromosome. The chromosomes are separated in anaphase. In telophase, chromosomes begin to uncoil, and nuclear membranes begin to form. Finally, *cytokinesis* divides the cytoplasm, producing two genetically identical daughter cells.

As the cell progresses from interphase into mitosis, chromosomes condense and attach to spindle fibers in preparation for cell division. Cytokinesis divides the cell's cytoplasm, resulting in two identical daughter cells.

Organisms that make genetically identical clones of themselves reproduce

Asexually

Describe how bacteria reproduce and how it's different from mitosis. -make sure you describe binary fission -Is this sexual or asexual reproduction of cells?

Bacteria reproduce through binary fission. Binary fission is simpler and faster than mitosis. It involves the duplication of one circular piece of DNA. This is asexual reproduction of cells.

Mitosis occurs in which types of cells?

Body cells

Unlike stem cells, most body cells cannot form different types of cells. For example, skin cells can make only skin cells, and nerve cells can make only nerve cells. Which statement best explains why skin cells could not become nerve cells?

Both types of cells have the same DNA, but each cell uses only part of the DNA message.

Explain the connection between the cell cycle and cancer development.

Cancers can form when cells divide out of control, bypassing checks in the cell cycle to continue growing inappropriately.

This includes a regular pattern of growth, DNA duplication and cell division

Cell cycle

List the major characteristics of Prophase (how do you identify it?) Sketch a cell in prophase with these characteristics (show 3 chromosomes)

Condensed chromosomes, no nuclear membrane (sometimes there can be), and spindle fibers

What is an example of internal factors at work to regulate cell division?

Cyclins (proteins that activate kinases which are enzymes that help control the cell cycle).

How are kinases dependent on cyclins to ensure a cell starts and stops dividing at an appropriate time?

Cyclins activate kinases, and the cyclins probably receive instructions on appropriate times for when to send signals.

What is another name for the division of the cytoplasm at the end of mitosis?

Cytokinesis

Mitosis is a nuclear division. What occurs at the very end of mitosis?

Cytokinesis (the division of the cytoplasm into two new daughter cells).

Apoptosis, or programmed cell death, is triggered during what biological processes?

DNA damage suffered by a cell; removal of certain tissues during embryonic development

As an embryo begins to organize, it first develops into a hollow ball with a flattened cluster of cells at one end. The outer layer is called the *ectoderm* and will become an organism's skin and nervous system. The cluster of cells forms a tube through the center of the ball that will become the inner lining of the digestive tract and other organs. This layer is known as the *endoderm.* As the tube forms, some cells from the cluster migrate into the cavity of the embryo to become the *mesoderm.* This layer will become muscle and bone and organs such as the kidneys.

Each layer in the blastocyst forms different structures in the developed organism. The outer layer forms the skin and nerves, the inner layer forms the lining of internal organs, and the middle layer forms muscle, bone, and some internal organs.

Describe how cell differentiation led to the development of a multicellular organism like yourself.

Embryonic development begins with producing a zygote. The zygote then undergoes a series of divisions to produce a mass of cells that become specialized through cell differentiation, which then forms a hollow ball. Then, the ball forms the endoderm, and then the ectoderm. Afterwords, the mesoderm is formed.

The rate of cell division is faster in

Embryos

When cells are signaled to stop dividing because they make contact with neighboring cells this is an example of an

External factor regulating cell division

Which term describes the resting phase of the cell cycle?

Interphase

What is mitosis' effect on the embryo?

It increases the number of cells in an embryo.

What is cell differentiation's effect on the embryo?

It increases the number of tissues in an embryo.

What is cytokinesis and why is it important? What would a cell look like if cytokinesis didn't happen?

It is important because it is the final step of the cell cycle. If cytokinesis didn't occur, there would be one large cell with two nuclei each containing a full set of chromosomes.

What happens if a mutation occurs in a segment of DNA that codes for normal internal or external factors? -what causes these mutations?

One example is that a person could get cancer (cell division is abnormal). Heredity mutations are inherited from a parent, and acquired mutations can occur from environmental factors or errors in DNA replication. Mutations are anything that can affect DNA replication.

Cell differentiation occurs in which type of cells?

Stem cells

Which types of cells can develop into a variety of specialized cells through differentiation?

Stem cells

Why are stem cells of great interest to researchers studying therapies for human diseases.

Stem cells can develop into any type of cell. So researchers want to place stem cells in tissues that need repairing because these cells can divide to make new, functional cells.

multipotent stem cells

Stem cells can develop into more than one cell type, but is much more limited.

Stem cells are a unique type of body cell that can *differentiate* to form a variety of specialized cell types. A stem cell can either divide into two new stem cells or it can divide to produce one stem cell and one specialized cell, such as a *neuron.* New advancements in science have allowed researchers to convert human skin cells to embryonic stem cells. This requires altering segments of DNA called *genes.* When these segments of DNA are expressed, the cell produces *proteins,* which carry out specific functions within the cell.

Stem cells can differentiate to form any type of specialized cell. Scientists are now able to convert differentiated cells back into stem cells by manipulating their genetic code.

pluripotent stem cells

Stem cells can give rise to several cell types.

The SA:V ratio of cell A is 6:1 and the SA:V ratio of cell B is 3:1. Describe these cells... -What is surface area and what is volume for a cell? -Which is bigger/smaller? -Which is most efficient in transport of materials with its environment?

Surface area is the area of the outside of the cell. Volume is the space inside the cell. Cell B larger than Cell A. Cell A is more efficient because it is smaller and it has more surface area to transport and absorb materials.

What are the principles of the cell theory?

The cell is the basic unit of life, all living things are made of cells, and all cells come from other cells.

Which events take place during mitosis but not during binary fission?

The duplication of organelles and the formation of a mitotic spindle. In binary fission, the duplicated chromosomes attach to opposite sides of the bacterial cell. As the cell grows, it pulls the chromosomes apart. When it is doubled in size, it undergoes cytokinesis, forming two new bacterial cells.

Describe what each layer of this gastrula stage of the embryo eventually differentiates into...

The ectoderm is the outer layer (skin cells and nervous system), the mesoderm is the middle layer (muscle, bone, and organs), and the endoderm is the inner layer (inner lining of the digestive tract/other organs).

What was the purpose of the identification of Whitefish and Onion root mitosis?

The purpose was to learn how to identify cells in different stages of mitosis.

What was the purpose of the identification of Whitefish and Onion root interphase?

The purpose was to learn how to tell if cells were in interphase or not.

What was the purpose of the cell size/agar lab?

The purpose was to learn that smaller cells with a greater SA:V ratio are more efficient at doing functions such as absorbing materials.

Is the rate of cell division greater in a child or an adult? Why do you think this is?

The rate of cell division is greater in a child because they have growth spurts, which requires more cells.

What was the purpose of the planarian regeneration lab?

To show how prokaryotic cells can regenerate and reproduce.

As cells grow larger, what happens to the surface area-to-volume ratio? How does this affect the cells' ability to grow further?

The surface area-to-volume ratio decreases as cells grow larger. The increase in cell volume, relative to surface area, makes it slower and more difficult to transport oxygen, nutrients, and waste across the cell membrane, thus limiting the growth of the cell.

If the DNA in all of your cells is exactly the same because of mitosis, how are there so many different types of cells?

There are so many different types of cells because of your genes and because of cell differentiation.

How can you tell the DNA has been duplicated before mitosis?

There will be double the amount of DNA in the nucleus.

What would happen if a cell lost the ability to divide and continued to grow to 10X it's normal size?

There would be more volume compared to the cell's surface area. As a result, there is less cell membrane for materials to pass through.

Which is true about Embryonic Stem Cells?

They can become any cell type in the body

Describe what a non or rarely dividing cell does in the cell cycle.

They carry out every day functions and sustain life.

How do tumor suppressor genes prevent cancer?

They inhibit proliferation, induce apoptosis, or guard the stability of the genome.

Why are cells small?

They need a large surface area compared to their volume, which ensures that materials can move into and out of the cell at adequate rates (to remain homeostasis).

Why is it important that all of your 46 chromosomes are replicated before cell division?

To carry information for making all of the cell's proteins which implement all the functions of a living organism and determine its characteristics.

How can you determine the surface area to volume ratio for a cell?

To find the SA: length•width•the number of sides To find the V: length•width•height SA:V

When a gene is expressed or "switched on" the instructions within that DNA are used

To make a protein

What is the role of mitosis and cytokinesis in eukaryotes?

To produce two daughter cells with identical genetic information, and to allow for growth and repair of an organism.

What was the purpose of the chicks incubating in the back for 21 days?

To see the certain conditions that some embryos need to develop.

What types of cells are produced during mitosis?

Two identical daughter cells

Describe what you learned from the cell size lab and why you were asked to learn it...

We learned that the smaller the cell is the more effective it is that moving materials into and out of the cell. We learned this because the size of a cell matters to function properly.

Why/when would internal or external signals activate genes to support apoptosis of cells?

When damaged cells, or cells, aren't needed in the body. Two examples are: the removal of the cells between an embryo's fingers or toes, or the removal of limbs and tail of an embryo.

How to calculate the volume of a cell

length × width × height

How to calculate the surface area of a cell

length × width × number of sides

Adult stem cells are?

multipotent

Which cell type would divide the least rapidly?

nerve cells

Where is DNA located in prokaryotic cells?

nucleoid of a cytoplasm

Embryonic stem cells are?

pluripotent

_ can become any of the three cell layers in a developing embryo (endoderm, mesoderm, ectoderm), but not the placenta surrounding the embryo.

pluripotent

Phases of mitosis in order

prophase, metaphase, anaphase, telophase

Which type of gene stimulates the cell cycle in a normal fashion?

proto-oncogene

Which cell type would divide the most rapidly?

skin cells

As cells become more specialized

some genes are turned off

Which of the following cells has the ability to form any tissue in the body? A cell that has the most potential, able to become any type of cell.

totipotent

Which type of gene inhibits the cell cycle in a normal fashion?

tumor suppressor gene

What is the end result of mitosis and cytokinesis?

two genetically identical cells