Cell Division Practice Questions

Correct answer: S phase

The S phase (Synthesis phase) is the part of interphase during which the cell's DNA is replicated. This ensures that each daughter cell receives a complete and identical set of chromosomes.

Correct answer: The nuclear envelope breaks down and chromatin condenses

Prophase is the first stage of mitosis where the genetic material condenses into visible chromosomes. During this stage, the nucleolus disappears and the nuclear envelope starts to disintegrate to allow spindle fiber attachment.

Correct answer: Spindle fibers

Spindle fibers, composed of microtubules, attach to the kinetochores of the chromosomes. They exert tension from opposite poles to align the chromosomes along the metaphase plate.

Correct answer: Production of two genetically identical diploid daughter cells

Mitosis is a form of equational division used for growth, tissue repair, and asexual reproduction. It results in two daughter cells that are genetically identical to each other and the original parent cell.

Correct answer: Anaphase

In anaphase, the centromeres split and the sister chromatids are pulled apart by the shortening of the spindle fibers. Once separated, each chromatid is considered an individual chromosome.

Correct answer: Cell plate

Due to the rigid cell wall, plant cells cannot pinch inward like animal cells. Instead, vesicles from the Golgi apparatus collect at the midline to form a cell plate, which eventually develops into a new cell wall.

Correct answer: Prophase I

Crossing over involves the exchange of genetic material between non-sister chromatids of homologous chromosomes. This happens during Prophase I and is a major source of genetic variation in offspring.

Correct answer: Four haploid cells

Meiosis involves two rounds of division following a single round of DNA replication. This produces four daughter cells, each containing half the number of chromosomes (haploid) as the original parent cell.

Correct answer: Two new nuclear envelopes form around the separated chromosomes

Telophase is the final stage of mitosis where chromosomes reach the poles and begin to de-condense back into chromatin. The nuclear envelope reforms around each set of chromosomes, resulting in two distinct nuclei.

Correct answer: Centromere

The centromere is the constricted region of a chromosome that holds sister chromatids together. It also serves as the attachment point for spindle fibers during cell division.

Correct answer: Pairs of chromosomes (one from each parent) that carry the same genes

Homologous chromosomes are pairs of chromosomes that are similar in shape, size, and gene position. One is inherited from the mother and one from the father, and they pair up during meiosis.

Correct answer: It reduces the number of chromosomes from diploid to haploid

Meiosis I separates homologous chromosomes rather than sister chromatids. This results in the chromosome count being halved (e.g., from 46 to 23 in humans), which is necessary to maintain a constant chromosome number after fertilization.

Correct answer: Cyclins and Cyclin-Dependent Kinases (CDKs)

Cyclins and CDKs are the internal regulatory proteins of the cell cycle. They control the transition between phases and can halt the cycle if DNA damage or incomplete replication is detected.

Correct answer: Cancer

Cancer is essentially a disease of the cell cycle. When the genes that regulate cell division mutate, cells may divide continuously, forming masses of cells called tumors.

Correct answer: Four functional sperm cells

Spermatogenesis is the male version of meiosis. It produces four haploid spermatids from a single primary spermatocyte, all of which eventually mature into functional sperm cells.

Correct answer: A non-dividing, resting state

The G0 phase is a quiescent period where cells exit the cell cycle. Some cells, like neurons, stay in G0 permanently, while others can be signaled to re-enter the cycle for repair or growth.

Correct answer: Anaphase I

In Anaphase I, the homologous pairs are pulled to opposite poles. Unlike mitotic anaphase, the sister chromatids stay together at their centromeres until Anaphase II.

Correct answer: Nondisjunction

Nondisjunction occurs when chromosomes fail to separate in either Meiosis I or II. This results in gametes with an abnormal number of chromosomes, which can lead to conditions such as Down Syndrome.

Correct answer: The random alignment of homologous pairs at the metaphase plate

Independent assortment occurs in Metaphase I when homologous pairs align randomly. Because each pair orients independently of the others, there are millions of possible combinations of maternal and paternal chromosomes in the resulting gametes.

Correct answer: Centrosomes containing centrioles

Centrosomes act as the main microtubule-organizing centers in animal cells. They duplicate during interphase and move to opposite poles to form the mitotic spindle that orchestrates chromosome movement.