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.

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.

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. 

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. 

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.

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.

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.

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.

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.

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.