High School Biology : Cell Division

Study concepts, example questions & explanations for High School Biology

varsity tutors app store varsity tutors android store

Example Questions

Example Question #31 : Cell Division

Which term refers to the microtuble structures that move the chromatids to opposite poles of a cell during mitosis?

Possible Answers:

Microfilaments

Spindle fibers

Kinetochores

Centrioles

Vesicles

Correct answer:

Spindle fibers

Explanation:

Spindle fibers are specialized microtubule structures that guide the movement of chromosomes and chromatids during mitosis. During mitosis, the spindle fibers will bind to a protein complex (known as the kinetochore) at the center of the chromosome. The kinetochore serves as an anchor, allowing the spindle fibers to retract and separate the sister chromatids. Centrioles serve as the opposite anchor point, keeping the other end of the spindle fiber attached to the pole of the cell.

Viscles are small membrane-bound sacs that can be used to transport proteins and other molecules either within the cell, or between the cell and the extracellular matrix. Microfiliments are another component of the cytoskeleton and are frequently associated with motility; the protein actin is a microfiliment.

Example Question #181 : Cell Biology

During which stage of mitosis do the chromosomes begin to move towards opposite ends of the cell?

Possible Answers:

Anaphase

Telophase

Prophase

Metaphase

Correct answer:

Anaphase

Explanation:

Recall PMAT mnemonic for remembering the steps in mitosis: prophase, metaphase, anaphase, telophase. Mitosis involves the separation of the (already-duplicated) chromosomes. The chromosomes condense, the mitotic spindle begins to form, and the nuclear envelope begins to break down during prophase. During metaphase, the chromosomes line up on the metaphase plate. In anaphase, the sister chromosomes begin getting pulled to opposite ends of the cell. Telophase is the opposite of prophase, and the cell undergoes cytokinesis.

Example Question #1 : Understanding Structures Of Mitosis

In mitosis, metaphase can be distinguished from the other stages most easily due to which of the following?

Possible Answers:

Chromosomes aligned in the middle of the plane by what is known as the metaphase plate. 

Metaphase is not a stage in mitosis. 

Chromosomes entangled with one another, enveloped in the nuclear membrane. 

Chromosomes that are being separated by the formation of the cell plate. 

Chromosomes are at separate poles with kinetochore attachments. 

Correct answer:

Chromosomes aligned in the middle of the plane by what is known as the metaphase plate. 

Explanation:

Metaphase, by definition, is the point in which the sister chromatids align themselves along the middle of the plane which is known as the metaphase plate. 

The responses explain interphase (chromosomes entangled with one another, enveloped in the nuclear membrane) and anaphase (chromosomes are at separate poles with kinetochore attachments). The other two responses are not phases of mitosis. 

Example Question #1 : Understanding Structures Of Mitosis

What is the role of the kinetochore? 

Possible Answers:

Perform a check that sister chromatids have been copied properly and are identical 

Bind sister chromatids together

Keep chromatin coiled

Signal the cell to enter metaphase

Act as an attachment point for spindle fibers

Correct answer:

Act as an attachment point for spindle fibers

Explanation:

Kinetochores are protein structures located near the center of chromatids during cell division. Each chromatid has its own kinetochore so that spindle fibers can attach and pull the sister chromatids to opposite ends of the dividing cell. Note that the kinetochore assembles on the centromere region. 

Example Question #1 : Meiosis

Which event takes place during anaphase II?

Possible Answers:

Sister chromatids line up in the center of the cell

Homologous chromosomes are separated

Homologous chromosomes line up in the center of the cell

Sister chromatids are separated 

Correct answer:

Sister chromatids are separated 

Explanation:

During prophase I, homologous chromosomes form tetrads along the center of the cell. Full chromosomes are pulled to each pole during anaphase I, resulting in two haploid cells at the end of meiosis I. During prophase II, sister chromatids align at the center of the cell in singular chromosome structures. These sister chromatids are separated during anaphase II, resulting in a total of four haploid cells.

Example Question #1 : Understanding Stages Of Meiosis

What is the first stage of meiosis during which a cell is considered haploid?

Possible Answers:

Prophase II

Telophase II

Metaphase I

Anaphase I

Correct answer:

Prophase II

Explanation:

A diploid cell will have two copies of each chromosome, known as a homologous pair. A haploid cell will only have one copy of each chromosome, though the chromosome may consist of two sister chromatids.

Diploid cell: (XX)

Haploid cell: (X)

During meiosis I, the cell is diploid because the homologous chromosomes are still located within the same cell membrane. Only after the first cytokinesis, when the daughter cells of meiosis I are fully separated, are the cells considered haploid. Following this first division, the cell begins meiosis II with prophase II, making this the first haploid meiotic stage.

Example Question #1 : Understanding Stages Of Meiosis

What occurs during the S phase of the cell cycle?

Possible Answers:

The cell grows in size, prepares mRNA and proteins, and prepares to divide

The cell's chromatin condenses and forms chromosomes

The cytoplasm splits and forms two diploid daughter nuclei

DNA is replicated, resulting in two identical sister chromatids attached at the centromere

The cell enters a state in which it neither divides, nor is preparing to divide

Correct answer:

DNA is replicated, resulting in two identical sister chromatids attached at the centromere

Explanation:

The S phase occurs between the G1 and G2 phases and is the stage during which DNA is replicated, and then checked for defects. Depending on the level of nutrients and energy available, the cell will either enter the G0 phase or the M phase.

During the G1 phase, the cell replicates organelles and grows in size. During the G2 phase, DNA is checked for damage and the cell prepares to divide. The M phase refers to mitosis, while the G0 phase refers to quiescence—a period during which the cell is not preparing for division.

Example Question #1 : Understanding Stages Of Meiosis

During which phase of meiosis does DNA begin to condense?

Possible Answers:

Telophase I

Metaphase II

Prophase I

Anaphase I

Metaphase I

Correct answer:

Prophase I

Explanation:

Mitosis is also known as "karyokinesis." "Karyo-" refers to the nucleus. (Remember that eu-KARY-ote means true ("eu-") nucleus, and pro-KARY-ote means before ("pro-") nucleus.) The "-kinesis" part of "karyokinesis" comes from the same roots as "kinetic" and refers to movement. Thus, mitosis is the movement of the nucleus. Packing of the DNA occurs in prophase of mitosis so that it's easier to move rather than having to move the loose chromatin. Think of moving forty-six strands of hundreds of yards of yarn—we would want it to be tightly coiled to make it manageable.

Example Question #1 : Understanding Stages Of Meiosis

Meiosis is the process by which a ___________ cell is formed from a ___________ cell.

Possible Answers:

haploid . . . diploid

diploid . . . haploid

diploid . . . diploid

haploid . . . haploid

Correct answer:

haploid . . . diploid

Explanation:

Meiosis is the process by which a haploid cell is formed from a diploid cell. The difference between haploid cells and diploid cells is that haploid cells contain one complete set of chromosomes, whereas diploid cells contain two complete sets of chromosomes. Meiosis involves the division of a diploid (2n) parent cell. The chromosomes are duplicated, but carry out two consecutive divisions. The result is four haploid (n) cells, each with half the number of chromosomes as the parent cell due to the separation of homologous pairs in meiosis I.

In contrast, mitosis is the process by which a diploid parent cell produces two diploid daughter cells.

Example Question #1 : Meiosis

Which three events most accurately describes what occurs in meiosis I?

Possible Answers:

Homologous chromosomes pair, cross over, then separate

Sister chromatids pair, cross over, then separate

None of these occur in meiosis I

Homologous chromosomes are duplicated, pair, then separate

Sister chromatids are duplicated, pair, then cross over

Correct answer:

Homologous chromosomes pair, cross over, then separate

Explanation:

In meiosis I, the homologous chromosomes have already been duplicated in S phase of interphase. The sister chromatids are identical at this stage. Homologous chromosomes pair in prophase I, forming tetrads. The tetrads then cross over, exchanging genetic material. Then, the genetically-mixed tetrads line up on the metaphase plate and are separated in anaphase I. Note that after the first meiotic division, the two daughter cells are nonidentical and are haploid.

Learning Tools by Varsity Tutors