Mitosis: The Fundamental Process of Life

These flashcards review key definitions, phases, checkpoints, implications, and medical relevance of mitosis.

What is mitosis?

A process of nuclear division in eukaryotic cells that produces two genetically identical daughter cells.

Approximately how many cells are replaced daily in an adult human via mitosis?

About 100 billion cells.

How long does a typical mitotic division take in human cells?

Roughly 1–2 hours.

How is mitosis distinct from meiosis?

Mitosis yields genetically identical somatic cells for growth and repair, whereas meiosis produces genetically unique gametes for sexual reproduction.

During which interphase sub-phase does DNA replication occur, and how many base pairs are copied in human cells?

S phase; approximately 6.4 billion base pairs.

Name the three stages of interphase in order.

G1 phase, S phase, G2 phase.

What key chromosomal change occurs during prophase?

Chromosome condensation makes the chromosomes visible under a microscope.

What are sister chromatids and how are they joined?

Two identical copies of a replicated chromosome joined at the centromere.

What happens to the nuclear envelope during prophase?

It breaks down, and the nucleolus disappears.

Which structures form the mitotic spindle and move to opposite poles?

Centrosomes, which nucleate spindle fibers (microtubules).

What is the metaphase plate?

An imaginary plane at the cell’s equator where chromosomes align during metaphase.

Why is the metaphase checkpoint vital?

It verifies that every chromosome is properly attached to spindle fibers, preventing segregation errors like aneuploidy.

Define aneuploidy and give an example.

An abnormal number of chromosomes; e.g., Trisomy 21 (Down Syndrome).

What molecular event initiates chromatid separation in anaphase?

Cleavage of cohesin proteins holding the sister chromatids together.

Why is anaphase typically the shortest stage of mitosis?

Because chromatid movement toward poles happens rapidly, lasting only a few minutes.

What reforms around each chromosome set during telophase?

A new nuclear envelope, creating two distinct nuclei.

What is cytokinesis in animal cells, and how does it physically occur?

Division of the cytoplasm by formation of a cleavage furrow that pinches the cell into two daughter cells.

List four primary biological purposes of mitosis.

Growth, tissue repair, replacement of old or dead cells, and asexual reproduction.

About how often are intestinal lining cells replaced through mitosis?

Every 3–5 days.

What is non-disjunction?

Failure of chromosomes to separate evenly, leading to daughter cells with abnormal chromosome numbers.

What proportion of cancers is associated with mitotic errors or checkpoint failures?

Over 90 percent.

Besides cancer, what other outcomes can result from mitotic errors?

Abnormal cell proliferation or programmed cell death (apoptosis).

Why is understanding mitosis important for medical research?

It provides insights into cancer, genetic disorders, and potential therapeutic targets.