AP Biology : Understanding Mitosis

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #11 : Understanding Mitosis

During which of the following mitotic phases will a cell be haploid?

Possible Answers:

Anaphase

None of these

Prophase

Metaphase

Correct answer:

None of these

Explanation:

Remember that a cell is defined as diploid if it possesses pairs of homologous chromosomes. During mitosis the cell always possesses homologous chromosomes. The segregation of chromosomes only involves the separation of sister chromatids to opposite sides of the cell, not the homologous chromosomes. The two daughter cells produced contain the same homologous pairs of chromosomes as the parent cell. A cell is therefore always diploid during mitosis and cytokinesis.

A cell will only become haploid during meiosis, when homologous chromosomes are separated during meiosis I and sister chromatids are separated during meiosis II.

Example Question #12 : Understanding Mitosis

Human somatic cells have 46 chromosomes. How many chromosomes are present in a human cell during metaphase of mitosis? 

Possible Answers:

Correct answer:

Explanation:

A chromosome carries the genetic material for a certain segment of the genome. A chromosome can consist of either one or two chromatids.

During metaphase, there are 46 chromosomes composed of two sister chromatids each that align at the metaphase plate. Then, during anaphase, these chromatids are separated and pulled to opposite poles of the cell. This separation results in 92 separate chromatids in the cell, which are considered 92 chromosomes.

Only germ cells will have 23 chromosomes. These haploid cells result from meiosis, rather than mitosis.

Example Question #13 : Understanding Mitosis

In which stage of mitosis does the nuclear envelope form?

Possible Answers:

Anaphase

Telophase

Prophase

Metaphase

Correct answer:

Telophase

Explanation:

During telophase the chromosomes have been sufficiently separated, and new nuclei can be formed. Telophase functions to prepare the cell for cytokinesis be sealing the chromosomes off from the cytoplasm in a new nuclear envelope.

The nuclear envelope first dissolves during prophase, allowing the chromosomes to migrate into the cytoplasm. They align at the center of the cell during metaphase. Sister chromatids are separated during anaphase, and the cell prepares for the final stages of division during telophase.

Example Question #14 : Understanding Mitosis

Which of the following processes occurs during anaphase of mitosis?

Possible Answers:

Chromosomes condense

Chromosomes decondense

Centrioles separate

The cell briefly contains 92 chromosomes

DNA is synthesized

Correct answer:

The cell briefly contains 92 chromosomes

Explanation:

During metaphase, chromosomes line up along the center of the cell. At this point, each chromosome contains two sister chromatids.

During anaphase, sister chromatids are separated but remain within the same cell cytoplasm.

A chromosome can consist of either one or two chromatid. A single chromatid is considered a chromosome once it has been separated from its pair. During anaphase, each of the cell's 46 chromosomes is split into singular chromatids, and each chromatid is considered a separate chromosome structure for a total of 92 chromosomes. Once the cell completes division, these chromatids are sequestered into separate nuclei and the cell returns to its normal diploid state.

Example Question #15 : Understanding Mitosis

Which of the following occurs during meiosis, but does not occur during mitosis?

Possible Answers:

Cytokinesis

Segregation of homologous chromosomes

Separation of sister chromatids

Chromosome condensation

Correct answer:

Segregation of homologous chromosomes

Explanation:

During mitosis we do not see separation of the homologous chromosomes. This is the reason that meiosis results in a reduction of ploidy and that mitosis does not. Separation of homologous chromosomes occurs after the formation of tetrads, during anaphase I of meiosis.

All of the other answers are processes that occur during both meiosis and mitosis. Both divisions require the condensation of chromosomes and eventual cytokinesis to produce daughter cells. Sister chromatids are separated during anaphase of mitosis, and during anaphase II of meiosis.

Example Question #16 : Understanding Mitosis

Which of the following does not happen during anaphase of mitosis?

Possible Answers:

Chromosome condensation

Sister chromatid separation

Migration of chromosomes towards opposite ends of the spindle

Degradation of securin

Correct answer:

Chromosome condensation

Explanation:

Anaphase is primarily characterized by the separation of the sister chromatids. This process occurs by degrading the protein securin, which binds the chromatids together. By degrading this protein, anaphase physically allows the sister chromatids to separate. Immediately after separation, the sister chromatids begin to migrate towards opposite ends of the spindle. Chromosome condensation occurs during prophase, not anaphase. 

Example Question #17 : Understanding Mitosis

In which stage of mitosis do the chromosomes line up along the equatorial plate?

Possible Answers:

Metaphase

Prophase

Telophase

Anaphase

Correct answer:

Metaphase

Explanation:

Metaphase is the stage of mitosis when chromosomes line up along the equatorial plate, so that they may be accurately segregated into two unique cells. Metaphase is the second phase of mitosis, following prophase.

During prophase, chromosomes condense and exit the nuclear envelope to align during metaphase. Anaphase follows metaphase, and is characterized by the separation of sister chromatids. Telophase is the final mitotic stage, during which the cell prepares for cytokinesis.

Example Question #18 : Understanding Mitosis

In animal cells, the process of cytokinesis occurs due to which of the following factors?

Possible Answers:

The fusion of vesicles near the center of the cell

The sliding of microtubules near the center of the cell

Actin filaments contracting around the circumference of the cell

The sliding of microtubules around the circumference of the cell

The movement of spindle fibers

Correct answer:

Actin filaments contracting around the circumference of the cell

Explanation:

Cytokinesis begins shortly after anaphase, when a contractile ring assembles near the equator of the cell. A cleavage furrow is formed and eventually, cytokinesis is completed. Actin filaments are capable of contraction, while tubulin polymers (microtubules) are generally used for cell structure. Microtubules form the spindle fibers used to separate sister chromatids during anaphase, but do not play a significant role in cytokinesis.

Example Question #19 : Understanding Mitosis

In chemotherapy, it is common to use drugs that can stabilize or depolymerize microtubules. Of the following statements, which is correct about these drugs?

Possible Answers:

The drugs disrupt endocytotic processes

The drugs disrupt the condensation of chromosomes

The drugs disrupt tumor movement

The drugs stimulate an immune response

The drugs disrupt mitosis

Correct answer:

The drugs disrupt mitosis

Explanation:

Microtubules are polymers of tubulin, and are components of the cytoskeleton. They are involved in mitosis, during which they are involved in the formation of the mitotic spindles. The drugs in chemotherapy are used in the disruption of mitotic processes. By disrupting microtubules, spindle fibers will be unable to form and the cell will be unable to complete anaphase.

Microtubules are not significantly involved in endocytosis, chromosome condensation, or the immune response. Microtubules are involved in cell motility, but movement of tumors is not a typical symptom of cancer. When tumors spread, it is generally due to cancerous cells being carried by the blood to other regions of the body, and is not directly linked to cell motility or microtubules.

Example Question #18 : Understanding Mitosis

Which of the following is not involved in mitosis?

Possible Answers:

Nuclear membrane disintegrates

Sister chromatids separate

Nucleolus disappears

Crossing over

Chromosome condensation

Correct answer:

Crossing over

Explanation:

Crossing over is the only answer choice that does not occur during mitosis. Crossing over occurs during prophase I of meiosis and involves swapping of genetic information between homologous chromosomes. This require the formation of tetrads, which does not occur during mitosis.

During prophase of mitosis chromatin condenses to form chromosomes and the nucleolus disappears. During prometaphase the nuclear membrane disintegrates. During anaphase of mitosis the sister chromatids separate. 

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