Chapter 7: Cell Division

Nuclear division divides the nucleus from the cytoplasm.

Both daughter cells are identical because the nucleus is divided.
Meiosis produces genetically variable daughter cells that contain half the genetic information of the parent cell.

The genetic material of the cell is contained in a single tightly coiled molecule of DNA.

There are two copies of the same chromosomes in diploid cells.
In a pair of chromosomes, one came from the maternal parent and the other from the paternal parent.
Humans have a total of 92 chromatids.

These features change when cell division begins.

During the telophase,kinesis begins.

The phases of the cellcycle are not required to be used in your responses to the AP exam.

If you omitted these words and only described the events in the correct sequence of occurrence, you would receive an equal amount of credit for your response.
The terminology that you will find in your textbook is based on the names of the phases, which are universally found in biology textbooks.

The nucleoli disappear and the chromosomes are formed.

As the MTOCs move apart from the nucleus, the development of the mitotic spindle begins.
When they move apart, the microtubule develops from each MTOC, increasing in length by the addition of tubulin units to the microtubule ends away from the MTOC.
Microtubules tug on the kinetochore, moving the chromosomes back and forth between one pole and the other.
There are other microtubules from each MTOC that do not attach to the chromosomes that are included in the completed spindle.

When the kinetochores pull the chromosomes apart, metaphase ends.

Each chromatid has a centromere and kinetochore.
Each chromatid is called a chromosome once separated from its sister.

The chromosomes are pulled to opposite poles by the shortening of the microtubules.

As tubulin units are uncoupled, the microtubules shorten.
The poles are pushed farther apart by overlapping microtubules from opposite MTOCs.
Each pole has the same number of chromosomes as the original cell, at the end of anaphase.

A nuclear envelope is restored around each pole.

The nucleus is divided into two daughter nuclei and the cytoplasm is divided into two cells.

Plants have Golgi bodies that migrate to the plane between the two new nuclei.

In animals, actin filaments form a ring between the two new nuclei.

As the actin filaments shorten, they act like purse strings to pull the cell into the center, dividing it into two daughter cells.

The cell begins a period of growth when the two processes are complete.

You can associate the labels G1 and G2 with growth and S with synthesis, but it's important to remember that growth takes place during all three phases.

The S phase is when the second DNA molecule is made.
Each of the chromosomes that appear at the beginning of the next division will be a pair of sister chromatids.
Materials for the next division are prepared during the G2 period.

Each daughter cell in the diploid state has two identical copies of the same chromosomes.

Each of the chromosomes will have one DNA molecule.
During the S phase of interphase, the second DNA molecule is duplicated from the first so that when the next division begins, each chromosomes will consist of two chromatids.

The two processes are very similar.

The two groups of divisions are meiosis I and II.
In meiosis I, the chromosomes pair at the metaphase plate and then they migrate to opposite poles.
In meiosis II, the chromosomes spread across the metaphase plate and sister chromatids separate and migrate to opposite poles.
Meiosis II is similar to meosis.
Each meiotic stage has a summary.

The phases of the cellcycle are not required to be used in your responses to the AP exam.

If you omitted these words and only described the events of meiosis in the correct sequence of occurrence, you would receive an equal amount of credit for your response.
The terminology that you will find in your textbook is based on the names of the phases, which are universally found in biology textbooks.

The nuclear envelope is broken down, the nucleus disappears, and the chromosomes are formed.

The kinetochore is attached to one of the members of the homologous pair.

The second member of each pair is connected to the Microtubule from the other pole.

Each pole will have half the number of chromosomes, but the other half will contain two chromatids.

In telophase I, the cells of many species begin cytokinesis and form cell plates.

After meiosis II, cytokinesis is delayed in other species.
A short interphase II may begin.
During this time, there is no replication of chromosomes.

There is no crossing over of genetic material in prophase I.

The chromatids migrate to their respective poles.

This is what happens when there is only half the number of chromosomes, except that now there is only half the number of chromosomes.

Each cell has half the number of chromosomes and only one chromatid.

The second chromatid is regenerated during the S phase of interphase, which is true.

The two daughter cells are clones of the original cell.
During the growth and development of multicellular organisms and for repair of existing cells, there is the occurrence of mitosis.
Asexual reproduction is common among plants and single-celled eukaryotes.

One of the haploid cells must combine with a second haploid cell to create a diploid cell in order to make a "normal" cell with the full set of chromosomes.

One copy of each chromosomes comes from one parent and the other from another.
Maternal and paternal heritage are represented by a pair of chromosomes in the diploid zygote.

There are 23 pairs of chromosomes in human cells.

Gametes are produced in the reproductive organs in humans.

Every daughter cell is the same as the parent cell.

Each homologue no longer represents a single parent.

Each pair of chromosomes go to opposite poles during metaphase I.

The orientation of a pair of chromosomes at the metaphase plate determines which pole they go to.
Each pair's orientation and separation is random.
For some pairs, the maternal chromosome may go to one pole, while the other may go to the other pole.

The gametes were joined.

New and variable combinations are created because of sexual reproduction.
The sperm thatfertilizes the egg is to a large degree a random event.
This event may be affected by the genetic composition of a gamete.
Some sperm may be faster swimmers and have a better chance of fertilization.

There are various factors that determine when a cell divides.

The volume of a cell increases more quickly than the surface area of the cell.

The surface area is larger when S/V is large.

The cell can respond efficiently to the outside environment.

Oxygen can diffuse into the cell and waste products can be quickly eliminated.

The volume is larger than the surface area when S/V is small.
The surface area might not be able to exchange enough substances with the outside environment to service the large volume of the cell.
At this point, cell division begins or cell growth stops.

These substances regulate cellular activities.

The amount of genetic material in the genome is limited.
The cell's genome size is constant as it grows.
As the G/V decreases, the cell's size exceeds the ability of its genome to produce enough materials for regulating cellular activities.

The cell cycle is controlled by various signals within the cell.

During the cell cycle, the cell evaluates internal and external conditions to determine whether or not to continue.

If damage to the DNA is detected, a repair is attempted.

If growth factors are not present, the cell proceeds no further through the cycle, remaining in an extended G1 phase.
The cells can leave the G0 phase and return to dividing if they need to replace injured tissue.

DNA repair is attempted if there is damage.

Apoptosis ensues if repair is unsuccessful.

CDKs are involved in moving the cell past the checkpoint.

Kinases phosphorylate other proteins.

TheProtein is ready to act once phosphorylated.

CDKs can be activated by cyclins.

Cyclins attach to CDKs and prepare them for activation.

phosphorylation is required for complete activation.

Without a cyclin attached, a CDK is inactive.

Each checkpoint has its own combination of CDK and cyclin that advances the cell cycle through the checkpoint.

The concentration of different cyclins varies during the cell cycle.

A specific cyclin and a specific CDK are combined as the cell cycle approaches each checkpoint.
An active site on the CDK is ready to be activated after the conformation change.
The activated cyclin-CDK complex activity that advances the cell cycle through the checkpoint is activated if the checkpoint conditions are met.
After the cycle phase, the cyclins are destroyed and new ones start to accumulate.

The cells have growth factors that cause them to divide.

Cell fragments called platelets circulate in the blood and contribute to the clotting mechanism.
The fibroblasts help heal damaged tissue.
There are more than 50 growth factors.

The surrounding cell density reaches a certain maximum when many cells stop dividing.

The majority of cells only divide when they are attached to an external surface, such as the side of a culture dish.

Cancer is a disease of the cell cycle.

A review of the material presented in this chapter is provided by the questions that follow.

They can be used to evaluate how well you understand the concepts.
AP multiple-choice questions are often more general, covering a broad range of concepts.
The two practice exams in this book are for these types of questions.

Four possible answers or sentence completions are followed by each of the following questions or statements.

The one best answer or sentence is what you choose.

Most of the fibers are composed of microtubules.

There are nine triplets of microtubules in a circle.

centrioles are found in all eukaryotic cells.

The cells have an apparatus.

Each answer can be used more than once or not at all.

Thekinesis begins.

The chymosomes migrate to opposite poles.

The cells replicate.

There is a normaldiploid cell in Figure A.

There are four symbols inside the cell.

Four chromosomes is the normal diploidnumber for the cells.

Each answer can be used more than once or not at all.

The questions that follow are typical of an entire AP exam question or just that part of a question that is related to this chapter.

There are two types of questions on the AP exam.

It takes about 20 minutes to answer a long free-response question.
Sometimes they offer you a choice of questions to answer.
6 minutes is the time it takes to answer a short free-response question.
diagrams can be used to supplement your answers, but a diagram alone is not adequate.

There are many of the same activities that occur during meiosis.

One stage of meiosis is distinct from the other.

Meiosis is a cause of genetic variation.

Explain how genetic variation is created.

Various processes regulate the cell cycle.

What goes wrong when a cell is taken by cancer is described in two or three sentences.

There are 92 chromatids with a total of 46 chromosomes at metaphase.

When the 2 chromatids of each chromosomes separate, metaphase ends and anaphase begins.
The 92 chromatids become 92 chromosomes when they are separated because each one has a complete DNA molecule.
There are 92 chromosomes destined for 2 daughter cells.

Each daughter cell has 46 chromosomes, each consisting of 1 chromatid.

The metaphase plate has a pair of homologous chromosomes.

During anaphase I, one member of each pair migrates to opposite poles.
If the cell started with 46 chromosomes, 23 of them move to each pole during anaphase I, so the total is still 46 chromosomes.

Most plants don't have centrioles.

During telophase, the chromosomes are uncoiled and the nucleus reappears.

The metaphase plate has the chromosomes arranged on it.

The beginning of anaphase is defined by the separation of the chromosomes into chromatids.

The chromosomes move from one pole to the other during anaphase.

During prophase, the two MTOCs migrate to opposite poles as the spindle apparatus develops between them.

During prophase, the nuclear and nucleolus are no longer present.

There is a phase of interphase called the S phase.

Since the union of two haploid gametes, the zygote has the same number of chromosomes as the parent.

The eight chromosomes are the same as in the parent cell.

A gamete has half the number of chromosomes as the parent cell.

Each pair of chromosomes would have one member.

Figure B has four chromosomes, but it does not have a single homologue of each pair.

chiasmata is a pair of Homologous chromosomes.

There are no events that can cause genetic differences between the daughter cells.

The daughter cells are clones.
During anaphase I, the random union of egg and sperm during fertilization, and crossing over during prophase I all contribute to genetic variation.

Each daughter cell had two chromosomes, each comprised of two chromatids, at the end of meiosis I.

Each of the chromosomes would be divided into two chromatids when anaphase II began.
One of the chromatids would migrate to one of the poles.

Each daughter cell would have two complete chromosomes if the cell began with four chromosomes.

The two chromosomes were notpaired on the metaphase plate.

The metaphase plate has four chromosomes spread out, unpaired.

The chromosomes would appear in pairs if this were metaphase I and only two if this were metaphase II.

In meiosis and metaphase I, the pairs of chromosomes occur.

During the condensation phase of meiosis, crossing over produces chromosomes with genetic material from both parents.

During sexual reproduction, the joining of gametes creates unique offspring.

When a cell's genes are damaged by radiation or chemicals, they may have changed.

If the gene product is damaged and not used to repair the DNA, it will be passed on to daughter cells.
Damage to the cell line may lead to a breakdown of cell cycle regulation and the cell line may become cancer.

The phases are prophase, metaphase, anaphase, and telophase.

The nuclear envelope and nucleolus disappear in prophase.
As centrioles migrate to opposite poles, microtubules form between them to form the spindle apparatus.
The kinetochores are attached to the centromeres of the chromosomes.
The chromosomes are lined up on the metaphase plate because the microtubules pulled them.
In anaphase, the sister chromatids of each chromosomes are separated and pulled to opposite poles.
The chromatids are divided into opposite poles in telophase.
There are nuclear membranes around each pole.
During telophase, the dividing of the cytoplasm begins.
Animals and plants have a cell plate that divides the cell.
If the mother cell began with a diploid number of chromosomes, the two nuclei that form at each pole will both be diploid.

The entire cell cycle includes both phases.

Interphase is a period of growth and is divided into three stages.
The first period of growth is called the G1 phase.

During the S phase, a second DNA molecule is replicated.

The cell prepares for a disease.
The M phase describes diseases.

There are many factors that can cause a cell to divide.

Cell size is limited by surface-to-volume and genome-to-volume ratios.

The ability to provide a surface large enough to meet import and export requirements of the cell decreases as the surface-to-volume ratio becomes smaller.

The amount of genetic material remains the same when the cell increases in size.
The ability of the nucleus to control the cell decreases as a result.

Cell activities in preparation for cell division are evaluated by various checkpoints during the cell cycle.

If the cell should enter the G0 state with no subsequent cell division, the G1 checkpoint will determine whether preparations should continue or not.
The chromosomes are attached to the microtubules by the M checkpoint.

Cell division is dependent on the presence of cyclin-dependent kinases, which regulate the cell cycle.

Growth factors that are produced by other cells influence cell division.

When neighboring cells are available for attachment or prevented by too many neighboring cells, cell division is promoted.

Like other metabolism activities, if and when a cell divides is determined by the activity of the enzymes.

Specific activities that prepare the cell for division are the result of specific points in the cell cycle.

Environmental factors, internal conditions, and genetic factors affect the production of these enzymes.

The normal cell-cycle checkpoint and other regulatory mechanisms fail in a transformed cell.

Most cancer cells don't need to attach to nearby cells to grow and divide.

The phases of the cellcycle are not required to be used in your responses to the AP exam.

If you omitted the words and only described the events in the correct sequence of occurrence, you would receive an equal amount of credit for your response.

You should write your answer in sections, responding to each part of the question separately and labeling each response with the appropriate letter.

Since you don't have a lot of time, you shouldn't spend a lot of it defining words.
The questions in the free-response section of the exam are designed to evaluate your understanding ofbiological processes.
You should use as much of the appropriate vocabulary as you can, but not define the process.
You can demonstrate an understanding of terminology and thebiological process by doing this.

Meiosis is divided into two groups, meiosis I and II.

Microtubules and the spindle apparatus are developed between the two MTOCs.

Synapsis occurs when there is a pair of chromosomes.

An exchange of genetic material occurs during synapsis.
The kinetochores in the centromeres of the chromosomes are connected to the microtubules.
The chromosomes are aligned on the metaphase plate.

Each member of a pair of chromosomes is pulled by the microtubules to different poles.

Sexual reproduction involves a reduction division called meiosis.

The number of chromosomes is halved so that daughter cells are haploid.
The gametes, sperm and eggs are formed in the testes and ovaries in humans.
Gametes form a diploid zygote, which grows into a multicellular organisms.
Multicellular haploid organisms may be produced by meiosis in other organisms.

During meiosis and sexual reproduction there are three points where genetic material is rearranged.

During metaphase I, there is an exchange of genetic material between non sister chromatids.

Genetic material from both parents can now be found in chromosomes.

In metaphase I, there are randomly aligned homologous chromosomes.
There is a random mixture of paternal and maternal chromosomes.
The zygote is a combination of a randomly selected egg and a sperm.
The daughter cells are genetically variable because of the random arrangements of chromosomes.

The phases of the cellcycle are not required to be used in your responses to the AP exam.

If you omitted the words and only described the events in the correct sequence of occurrence, you would receive an equal amount of credit for your response.