High School Biology : Understanding Structures of Mitosis

Study concepts, example questions & explanations for High School Biology

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Example Questions

Example Question #1 : Understanding Structures Of Mitosis

Mitosis has four phases. List the phases in the correct order.

Possible Answers:

Prophase, metaphase, anaphase, telophase

Prophase, metaphase, telophase, anaphase

Prophase, anaphase, metaphase, telophase

Metaphase, anaphase, telophase, prophase

Telophase, anaphase, prophase, metaphase

Correct answer:

Prophase, metaphase, anaphase, telophase

Explanation:

The correct order to the phases is: prophase, metaphase, anaphase, telophase.

During prophase, the nuclear membrane dissolves and the DNA condenses into chromosomes. The chromosomes travel to the center of the cell during metaphase and align, allowing spindle fibers to bind to the center of each chromosome. The spindle fibers contract during anaphase, separating the sister chromatids and pulling them to opposite poles of the cell. During telophase, the nuclear membrane begins to re-form and a ring of contractile filaments begins to pinch the cytoplasm to create two separate daughter cells (this is known as the cleavage furrow). Following telophase, the daughter cells completely separate; the division of the cytoplasm is called cytokinesis and is often considered a separate event from mitosis.

Example Question #2 : Understanding Structures Of Mitosis

Starting from a single parent cell, what are the results upon completion of one round of mitosis?

Possible Answers:

Two identical diploid cells

Four nonidentical haploid cells

Two nonidentical diploid cells 

Four idendical diploid cells

Four nonidentical diploid cells

Correct answer:

Two identical diploid cells

Explanation:

The process of mitosis involves separating the already duplicated chromosomes (sister chromatids). The parent cell doubled its DNA during the S phase of interphase so that it now has four copies of each gene (two copies of each allele). In humans this is equivalent to two copies of all 23 chromosomes from the mother, and two copies of all 23 chromosomes from the father, sometimes called 2x2n or 4n depending on the textbook.

During division, each chromosome is divided into its component chromatids. The result is a single copy of each chromosome (two copies of each gene, one from the mother and one from the father) in each daughter cell. Because there are two copies of each gene in the daughter cells, they are considered diploid. Sister chromatids are identical genetic copies; separating sister chromatids will result in identical daughter cells.

In contrast, the final product of meiosis is four nonidentical haploid cells. Each daughter cell at the end of meiosis carries only one copy of each gene (haploid) and is nonidentical to the other three daughter cells due to the phenomenon of independent assortment.

Example Question #3 : Understanding Structures Of Mitosis

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

Possible Answers:

Kinetochores

Vesicles

Centrioles

Microfilaments

Spindle fibers

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 #4 : Understanding Structures Of Mitosis

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

Possible Answers:

Anaphase

Prophase

Telophase

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 #5 : 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 that are being separated by the formation of the cell plate. 

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

Chromosomes are at separate poles with kinetochore attachments. 

Metaphase is not a stage in mitosis. 

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

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 #191 : Cell Biology

What is the role of the kinetochore? 

Possible Answers:

Act as an attachment point for spindle fibers

Signal the cell to enter metaphase

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

Keep chromatin coiled

Bind sister chromatids together

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. 

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