AP Biology : Understanding Mitosis

Study concepts, example questions & explanations for AP Biology

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Example Question #1 : Understanding Mitosis

How is metaphase of mitosis defined? 

Possible Answers:

Centrioles begin to move towards opposite poles of the cell.

Two distinct cells begin to form and separate from one another.

Sister chromatids begin to separate and form independent chromosomes.

DNA begins to replicate.

Chromosomes move towards the center or equator of the cell. Chromatids have not separated.

Correct answer:

Chromosomes move towards the center or equator of the cell. Chromatids have not separated.

Explanation:

Metaphase is defined when chromosomes move towards the equator of the cell.

Other answers refer to other stages of mitosis. Sister chormatids separate during anaphase, two distinct cells form during telophase, centrioles move towards opposite poles of the cell during prophase, and DNA replication happens during interphase.

Example Question #2 : Understanding Mitosis

During which phase of mitosis do sister chromatids separate?

Possible Answers:

Prophase

Telophase

Anaphase

Metaphase

Correct answer:

Anaphase

Explanation:

During anaphase, the third stage of mitosis, the spindle fibers cause sister chromatids to break apart, and they are subsequently moved to opposite sides of the cell.

Chromosomes condense during prophase, align during metaphase, separate during anaphase, and are relocated during telophase.

Example Question #2 : Understanding Mitosis

During which phase of mitosis do chromatids condense?

Possible Answers:

Anaphase

Telophase

Prophase

Metaphase

Correct answer:

Prophase

Explanation:

Chromatids condense during prophase, the first stage of mitosis. This allows the abundant amount of DNA to be organized into relatively small and tightly packed structures that can be aligned and separated later in mitosis. This also signifies the conversion of the DNA from loosely packed euchromatin to tightly packed heterochromatin.

Chromosomes condense during prophase, align during metaphase, separate during anaphase, and are relocated during telophase.

Example Question #4 : Understanding Mitosis

Which of the following actions occurs during telophase of mitosis?

Possible Answers:

Nuclear membranes dissolve

The nucleolus dissolves

Chromosomes line up at the center of the cell

Cytokinesis

Correct answer:

Cytokinesis

Explanation:

Cytokinesis, the process of the cytosol splitting into two daughter cells, occurs during telophase, the last phase of mitosis. Chromosomes line up at the metaphase plate during metaphase, while the nuclear membranes disappear and the nucleolus dissolve during prophase.

Example Question #3 : Understanding Mitosis

During which phase of the cell cycle is the nuclear envelope not intact?

Possible Answers:

G1 phase

Telophase

S phase

Anaphase

Early prophase

Correct answer:

Anaphase

Explanation:

During anaphase the sister chromatids are pulled apart by the mitotic spindle and move to opposite ends of the cell. The nuclear membrane begins to break down at the very end prophase and is completely deteriorated during metaphase, when the chromosomes align. It is still fully formed during early prophase. The membrane begins to reconstruct during telophase, but is not fully intact again until cytokinesis.

The S phase, which is when the cell duplicates its DNA, and the G1 phase, during which the cell grows, are phases of the cell cycle that are not involved in mitosis, known as interphase. The nuclear membrane is only disrupted during mitosis, and is thus intact during all stages of interphase.

Example Question #3 : Understanding Mitosis

Chromatid separation is associated with what phase of mitosis?

Possible Answers:

Prophase

Telophase

Anaphase

Metaphase

Correct answer:

Anaphase

Explanation:

During anaphase, the chromatids aligned on the equator of the cell are separated and pulled to opposite ends of the cell.

Prophase involves the condensation of chromatin into chromosomes and the removal of the nuclear envelope. The chromosomes align at the equatorial plate during metaphase and are pulled apart by the mitotic spindle fibers during anaphase. The chromatids begin to decondense during telophase, and the nuclear envelopes begin to form again.

Example Question #522 : Ap Biology

Which choice below properly matches the stage of mitosis with its description?

Possible Answers:

Telophase: two new nuclei form, each containing a group of migrated chromosomes

Anaphase: chromosomes replicate and the cell proceeds through multiple pre-mitotic checkpoints

Prophase: pairs of chromosomes line up along the center of the cell

Metaphase: chromosome pairs separate and migrate to opposite ends of the cell, propelled by the shortening mitotic spindle

Anaphase: chromatin condenses and a structure made up of microtubules forms

Correct answer:

Telophase: two new nuclei form, each containing a group of migrated chromosomes

Explanation:

The four mitotic stages included among these choices are prophase, metaphase, anaphase, and telophase, which occur in that order. The initial stage, prophase, involves chromosome condensation from chromatin and the formation of the spindle apparatus from microtubules. In metaphase, chromosome pairs line up in the center of the cell at a location called the metaphase plate. Anaphase involves the shortening of the microtubular spindle fibers, which forces chromosome pairs to migrate to opposite ends of the cell. Finally, telophase involves the formation of two new nuclei. Following telophase is cytokinesis, the final separation of the cytoplasm and other organelles of the two cells, and the sealing of the plasma membrane. Some references will include interphase, a period of rest, chromosome replication, and cellular checkpoints. Though not a part of mitosis itself, interphase separates successive mitotic divisions and acts as a time of cellular rest. In any case, the only properly matched definition above was that of telophase, the final stage of mitosis.

Example Question #4 : Understanding Mitosis

What is a centromere?

Possible Answers:

An organelle that organizes microtubules

A protein made mostly of tubulin

A protein that holds sister chromatids together

The site of association of sister chromatids

Correct answer:

The site of association of sister chromatids

Explanation:

Centromeres are the areas of chromosomes where sister chromatids are associated. They also have the important function of serving as the attachment site for microtubules of the mitotic spindle. Centromeres are not made of protein or microtubules.

Example Question #9 : Understanding Mitosis

The mature form of a newly discovered species of eukaryote contains 12 chromosomes and exists in the diploid state. In this new species, how many chromosomes are present in a mitotic cell immediately after the sister chromatids have separated?

Possible Answers:

Correct answer:

Explanation:

When sister chromatids are still connected, they are only considered one chromosome. As soon as they separate, however, each sister chromatid is considered a chromosome.

Two chromatids in one chromosome: (X)

Two separated chromatids: (/\)

Because the question states immediately after the sister chromatids have separated, our yeast cells would have 24 chromosomes within the mitotic cell. Once mitosis is completed, each daughter cell would have 12 chromosomes. The question refers to a unique period during which all replicated genetic material is present within a single cell, but separated into fragments that constitute 24 total chromosomes.

Example Question #45 : Cellular Division

Presence of nuclear membrane indicates that the cell is in which of the following phases?

Possible Answers:

Metaphase

Interphase

Telophase

Prophase

Correct answer:

Interphase

Explanation:

Remember that the nuclear membrane is disassembled during prophase of mitosis. It remains absent through the duration of mitosis until it begins to reassemble during telophase. The nuclear membrane is thus absent during prophase, metaphase, and telophase.

The nuclear membrane is present (and essential) during all periods of interphase. The main functions of interphase are the synthesis of cellular proteins, DNA replication, and cellular growth. These processes require proper housing of the DNA and transport of mRNA across the nuclear membrane.

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