Biology, Chapter 6, Smartwork

Place the phases of mitosis in the correct order.

prophase, metaphase, anaphase, telophase (PMAT)

Dogs have 78 chromosomes in their somatic cells. How many chromosomes do their gametes have?

39 Gametes have half the number of chromosomes of somatic cells. Page 105

How many chromosomes will be in a body cell of an organism if there are 20 chromosomes in the organism's unfertilized egg?

40 Eggs are haploid, which means they have half the number of chromosomes in a diploid body cell. Page 104

What percentage of males survive prostate cancer?

81.1%

A human has 46 total chromosomes. How many total chromatids are present in a human cell at the start of mitosis?

92

A mutated cell does not respond properly to checkpoints in the cell cycle. What is the most likely outcome of this mutation?

A cell that divides when it should not One of the checkpoints in the cell cycle ensures that cells divide at the appropriate time. Page 104

What is a somatic cell?

A normal body cell A somatic cell is a normal diploid body cell. Page 105

Which is correct concerning types of cell division?

Binary fission and mitosis produce cells identical to the parent cell.

What is the most likely outcome of cell cycle checkpoints being ignored?

Cancer develops.

What is the most likely outcome for cells resulting from a parent cell with a G1 phase that is shorter than normal?

Cells will be smaller than normal.

________ are points in the cell cycle where cells stop to assess their progression.

Checkpoints Cells pause at critical points in the cell cycle to ensure that the events are occurring properly. These points, called checkpoints, are known to occur during G1 phase, S phase, G2 phase, and M phase (mitosis). Page 104

Which of the following processes divides the cytoplasm of cells following mitosis?

Cytokinesis Cell division occurs through two processes: nuclear division and cytoplasmic division. Nuclear division evenly partitions the chromosomes, whereas cytokinesis separates the contents of the cytoplasm, which includes organelles and other cellular structures. Page 102

Which of the following factors might cause a cell to pause in a phase of the cell cycle?

Damage to DNA Cells will not continue through mitosis if their genetic material has been damaged. Damaged DNA that is transmitted to daughter cells may lead to cancer. Page 104

Which of the following organisms is likely to have the least complicated form of cell division?

Disease-causing bacterium

Which of the following are observations from the two failed experiments mentioned in this chapter?

Forty percent of the eggs resulting from the control mouse oocytes were showing chromosomal defects. A component of the experimental system, besides the experimental treatment, affected human breast tumor cell growth and development. The hormone estrogen caused human breast tumor cell growth.

Sort the following statements as they apply to meiosis I only, meiosis II only, or both.

Meiosis I: - The cell begins this phase as a diploid cell. - Homologous pairs of chromosomes line up at the center of the cell before separating. - Independent assortment occurs here. - Two cells form as a result of cytokinesis. Meiosis II: - The cell begins this phase as a haploid cell. - Pairs of sister chromatids are pulled apart during anaphase. - Four cells form as a result of cytokinesis. Both: - Cytokinesis follows this step. - Haploid cells result.

In what phase of meiosis does the process of independent assortment of chromosomes begin—when maternal and paternal homologues line up randomly at the equator of the cell?

Metaphase I

You are looking through a microscope at cells undergoing meiosis. You see a cell that has homologous pairs of chromosomes lined up down the middle of the cell. What stage is this cell in?

Metaphase I Homologous pairs of chromosomes line up in metaphase I Page 105

Sort the following statements as they apply to prokaryotic cell division or eukaryotic cell division.

Prokaryotic: - Replicates circular chromosomes - Cells reproduce via binary fission. Eukaryotic: - Replicates linear chromosomes - Cells reproduce via mitosis or meiosis. - DNA is contained in a nucleus. Both: - Can generate clones - Can undergo asexual reproduction

The nuclear envelope breaks down during which phase of mitosis?

Prophase The nuclear envelope breaks down to allow the spindle microtubules to attach to and capture the replicated chromosomes. This process occurs during prophase. Page 102

You are looking through a microscope at cells undergoing meiosis. You see one cell where the chromosomes are condensing and the nuclear membrane is breaking down. What stage is this cell in?

Prophase I

Arrange the following steps of meiosis in the correct order.

Prophase I, Metaphase I, Anaphase I, Telophase I and Cytokinesis I, Prophase II, Metaphase II, Anaphase II, Telophase and Cytokinesis II

What happens at the first checkpoint of the cell cycle (after G1)?

The nutrient level in the cell is checked to see if there is an adequate nutrient supply. The size of the cell is checked to determine if the cell is large enough at that point. The genetic information of the cell is checked to see if the DNA is undamaged.

Which of the following statements are true about cancer in males?

The prostate is the site with the highest rate of incidence of cancer in males. The lung and bronchus is the most deadly site of cancer in males.

A human liver cell begins its cell cycle. Which statement is correct concerning the number of genes in this cell as it proceeds?

There are four copies of each gene during G2. G2 follows S phase in which chromosomes are replicated. Because the pairs of chromosomes are homologous, there are four copies of each gene.

A human cell begins meiosis. Which statement is correct concerning the number of genes in this cell's daughter cells as it proceeds through the cell cycle?

There is one copy of each gene in each daughter cell at the end of telophase II. At the end of meiosis, each haploid daughter cell has one copy of each gene because each haploid daughter cell has only one of the two homologous chromosomes. Page 105

What is the outcome of mitosis?

Two cells that are identical to each other and identical to the parent cell

You are looking through a microscope at cells undergoing mitosis. You see a cell that has chromosomes being pulled apart to opposite sides of the cell. What stage is this cell in?

anaphase

Chromosomes are lined up in the middle of the cell during

metaphase

You are looking through a microscope at cells undergoing mitosis. You see a cell that has chromosomes lined up down the middle of the cell. What stage is this cell in?

metaphase

The second division of meiosis is essentially

mitosis that begins with two haploid cells and ends with four haploid cells. The purpose of meiosis II is to separate the attached duplicated sister chromatids present in the haploid cells following meiosis I. This is essentially what mitosis does, only with diploid cells instead of haploid. Page 105

The form of eukaryotic cell division that produces two genetically identical cells is

mitotic division Eukaryotic cells divide asexually via mitotic division. Because genetic material is symmetrically partitioned into two nuclei, this process produces genetically identical offspring called daughter cells. Page 102

When does replication of DNA occur in preparation for meiosis?

only once before meiosis starts Replication occurs once before meiosis begins. Page 105

A newly discovered organism has 18 total chromosomes. How many chromatids are present at the beginning of mitosis in this organism's cells?

36

How long is a cell cycle?

It depends on the cell type.

Which of the following are reasons the cell cycle will pause at a checkpoint?

-Cell size is too small. -Nutrient supply in the cell is too low. -DNA is damaged. -Chromosome replication is incomplete. A cell should pause for any of these reasons. Page 104

Meiosis and fertilization introduce genetic diversity in multiple ways. Place the following processes that introduce genetic diversity in the offspring in order by when they occur, from the beginning of meiosis I until after its completion.

1. Crossing-over 2. Independent assortment 3. Fertilization

During meiosis I, which process would generate gametes that are identical to your mother's or father's gametes? Assume that crossing-over does not occur and that the cell divides along its vertical axis (to the left and to the right).

All of the chromosomes you inherited from your mother align on the right side of the cell center. All the chromosomes you inherited from your father align on the left side of the cell center. This is the only situation that would cause your gametes to be identical to your parents' gametes. Page 108

A new chemical has been discovered. This chemical blocks replication. What organisms will this chemical damage?

All organisms will be damaged.

In which of the following stages of mitosis would you expect to see sister chromatids be separated?

Anaphase Sister chromatids separate and become individual chromosomes during anaphase of mitosis. During telophase they will be packaged into daughter nuclei, and ultimately, during cytokinesis, they will wind up in separate cells. Page 102

Why did it make sense that the BPA leaching from the corroded plastic in Hunt's experiment could have affected the chromosomes of the mouse egg cells?

BPA had been utilized as a hormone replacement therapy in the 1930s for women who needed estrogen.

What is the likely outcome if the cells do not pause at the checkpoint?

Cancer Proceeding forward in the cell cycle despite incomplete DNA replication can result in cancer. Page 105

Some fungi produce cells that are multinucleate, which means that they have more than one nucleus. What is most likely unusual about the cell cycle in the parent cells of these multinucleate cells?

Cytokinesis does not occur.

In 1989, biologists Ana Soto and Carlos Sonnenschein at Tufts University in Massachusetts were studying how the hormone estrogen regulates the growth of cells in the female reproductive system, specifically in human breast tumor cells. Suddenly, the cells in plastic containers were growing without the presence of estrogen. Which of the following statements are true about this experiment?

Estrogen activates mitotic division in these cells. Nonylphenol mimics the action of estrogen. Nonylphenol in the plastic tubes of the cell culture activated mitotic division.

A cell can pull out of which phase in the cell cycle to enter the G0 resting phase?

G1 Phase

You are testing a new drug that blocks cell division by preventing replication. After treating cells with the drug, you wait several hours. What stage do you expect to find most cells in?

G1 Phase

Put the phases of the cell cycle in a newborn cell in the correct order from first to last.

G1 Phase, S Phase, G2 Phase, Mitosis, Cytokinesis

You are testing a newly discovered chemical called Chemical X. Chemical X interferes with DNA replication, resulting in only some chromosomes being replicated. Which checkpoint should cells stop at?

G2 checkpoint A checkpoint right after the S phase in G2 should detect the problem. Page 105

The total weight of DNA in a human cell before replication is 6 picograms. Which choice lists the correct weight for the stage?

G2 phase = 12 picograms

In each of your homologous chromosome pairs, you inherited one chromosome from your mother and one from your father. Non-sister chromatids will exchange pieces of DNA during meiosis. What is the effect of this exchange?

Increased genetic diversity Crossing-over is one mechanism to increase genetic diversity in gametes. Page 108

During which of the following phases of mitosis do replicated chromosomes line up at an invisible plane along the center of the cell?

Metaphase During mitosis, replicated chromosomes are pushed back and forth until they wind up in the center of the cell. The mitotic spindle is the structure that relocates chromosomes in this fashion. At metaphase the replicated chromosomes line up at the metaphase plate, an invisible plane along the center of the cell. Page 102

Does mitosis or meiosis occur more often during a human lifetime?

Mitosis occurs more often. It creates and replaces every cell in the body except for the gametes. Mitosis occurs much more often as it is responsible for the replication and replacement of somatic cells while meiosis only produces gametes. Page 105

Based on the figure shown, a complete cell cycle consists of which of the following phases?

Mitosis, cytokinesis, G1 phase, S phase, and G2 phase The cell cycle includes the following phases: G1, S, G2, and mitosis followed by cytokinesis. These phases span the "birth" of a cell to the time when this same cell divides and creates daughter cells.

Which of the following apply to the action of nonylphenol?

Nonylphenol gives permission to the cell to divide when it should not divide. Nonylphenol interferes with the G0 checkpoint. Nonylphenol interferes with the G1 checkpoint.

Which is true of homologous chromosomes?

One comes from your father, the other from your mother. In a homologous chromosome pair, one chromosome is from the mother, and one chromosome is from the father. Page 105

Replication of a cell's genetic material occurs during

S phase

When are sister chromatids made?

S phase

You are investigating a new chemical labeled as an inhibitor of DNA synthesis. At what phase would the addition of this chemical cause the most damage to the cell cycle?

S phase

Where are checkpoints found in the cell cycle?

Several places in both interphase and mitosis

Which statement is correct about where sister chromatids end up after cell division is complete?

Sister chromatids end up in different cells. Sister chromatids are separated into different cells. Page 105

How is the second cell cycle checkpoint (after G2) different than the first?

The DNA is checked to make sure it is fully replicated.

Which of the following statements apply to cancer in females?

The breast is the most common site of incidence of cancer in females. Cancer of the lung and bronchus is the most deadly type of cancer in females.

Which of the following steps occur during prophase of mitosis?

The chromosomes condense. The nuclear envelope breaks down. The chromosomes attach to the mitotic spindle.

Which statement identifies a difference between eukaryotic and prokaryotic cell division?

The nuclear membrane must be disassembled and reassembled during mitosis and meiosis in eukaryotes, but not during binary fission in prokaryotes.

Humans have a total of 46 chromosomes. Which is true of sister chromatids in humans?

They are exactly identical to each other.

What purpose does crossing over and independent assortment play in cell division?

To help add genetic diversity to daughter cells Along with random fertilization, these processes help to promote genetic diversity among daughter cells. Diversity is important since it is the raw material that drives the process of evolution. Page 108

Which of the following is a reason why a cell might undergo mitosis?

To repair damaged tissues Mitosis is used for asexual reproduction, organism growth, and repair of tissues. Production of egg and sperm cells and increased genetic diversity are accomplished through meiosis. Page 102

What is the purpose of checkpoints in the cell cycle?

To stop the cell from going on in the cell cycle if there are problems A checkpoint makes sure the cell is functioning properly before the next step in the cell cycle. Page 104

Which is the best definition for the term "chromatid"?

an individual molecule of a replicated chromosome

Select all the types of cell division that are considered asexual.

binary fission mitosis

Sister chromatids are held together at a region called the

centromere. Chromosomes duplicated during S phase form two sister chromatids that are held together at the centromere. During the process of mitosis, the sister chromatids are pulled apart at the centromere. Eventually these two chromatids wind up in separate cells. Page 102

If you observed one skin cell becoming two identical skin cells, what would you never observe?

crossing-over

Versions of genes, or alleles, that are found on the same chromosome will be inherited together. What process can occur that results in new combinations of alleles on a chromosome?

crossing-over During crossing-over, homologous chromosomes exchange pieces, resulting in different combinations of alleles on a chromosome. Page 108

In both mitosis and meiosis II, sister chromatids separate during anaphase, but there are _____ haploid daughter nuclei produced by meiosis II compared to ______ diploid nuclei produced by mitosis.

four; two Meiosis produces four haploid daughter nuclei while mitosis produces two diploid daughter nuclei. Page 105

Cells that enter into G0 phase

have entered into a nondividing state.

During crossing over,

homologous chromosomes exchange genetic information. During crossing over, maternal and paternal homologues pair up and exchange segments of DNA during prophase I of meiosis. The result is that daughter cells are not identical to the parent cell that produced them. Page 108

What is the longest part of the cell cycle?

interphase

When do sister chromatids separate in meiosis?

meiosis II Sister chromatids separate in meiosis II during Anaphase II. Page 105

Mitosis is most similar to ______ because in both stages, _____.

meiosis II, sister chromatids separate. In both mitosis and meiosis II, sister chromatids separate. Page 105

A characteristic that distinguishes meiosis from mitosis is

the total number of chromosomes present in daughter cells. Page 105

A replicated chromosome consists of

two sister chromatids. A replicated chromosome consists of two sister chromatids that are held together at the centromere. During S phase, the replicated chromosomes are produced in preparation for mitosis. It is during mitosis that the replicated chromosome is split in two. Page 102