Week 9 Quiz

A skin cell near a healing scrape is getting ready to divide. In which part of the cell cycle does it copy its DNA?

Select one.

• The S phase, before mitosis begins
• Prophase, as the long chromosomes condense into rods
• Anaphase, as the sister chromatids separate and move apart
• Cytokinesis, as the cytoplasm divides into two cells

After the S phase, a duplicated chromosome has the familiar X shape. How should that X be counted?

Select one.

• As two chromosomes joined at the centromere
• As one chromosome made of two sister chromatids
• As one chromatid made of two chromosomes
• As half a chromosome waiting to be copied

Which list gives the phases of mitosis in the order they happen?

Select one.

• Prophase → anaphase → metaphase → telophase
• Metaphase → prophase → anaphase → telophase
• Prophase → metaphase → anaphase → telophase
• Telophase → anaphase → metaphase → prophase

Under a microscope, a cell shows two groups of chromosomes moving toward opposite ends of the cell. Which phase is it in?

Select one.

• Prophase
• Metaphase
• Telophase
• Anaphase

True or false: mitosis produces four genetically unique cells, each with half the parent cell's chromosome number.

True or false.

• True
• False

A cell at the tip of an onion root has finished telophase. How does it divide its cytoplasm?

Select one.

• It builds a cell plate, since it has a cell wall
• It pinches in two at a cleavage furrow, the way an animal cell does
• It copies all of its DNA again before it is able to split
• It skips cytokinesis and stays as one cell holding two nuclei

In the onion root tip example (illustrative), 100 cells were counted: 80 in interphase, 9 in prophase, 4 in metaphase, 3 in anaphase, and 4 in telophase. What is the mitotic index?

Select one.

• 80%
• 20%
• 25%
• 9%

Which statement best describes the role of the tumor suppressor p53?

Select one.

• It pushes the cell cycle forward like an accelerator stuck down
• It copies the DNA during the S phase
• It detects damaged DNA and pauses the cycle for repair or triggers apoptosis
• It builds the cell plate during cytokinesis

Which of these are jobs that mitosis does in a living thing? Select all that apply.

Select every option that applies.

• Growth of a body by adding cells
• Repair of a scraped knee
• Making egg and sperm cells
• Asexual reproduction, as when a plant cutting grows into a new plant
• Halving the chromosome number before fertilization

In prophase, the nuclear envelope breaks down. Which organelle does that envelope surround, and what is that organelle's job?

Select one.

• The mitochondrion, which makes ATP for the cell
• The Golgi apparatus, which modifies, sorts, and ships
• The lysosome, which breaks down the cell's waste
• The nucleus, which holds the DNA