Cell Cycle, Mitosis, and Meiosis

What is the average duration of the cell cycle?

Approximately 24 hours.

What is G0 phase?

An inactive resting phase that may last indefinitely.

What are the active phases of the cell cycle?

M phase and interphase.

Which phases are included in interphase?

G1, S, and G2.

In which cells does M phase occur?

Actively dividing cells.

What happens during G1 phase?

The cell grows, performs normal functions, duplicates organelles, and synthesizes proteins.

What does the G1 checkpoint verify?

DNA integrity, appropriate cell size, and the presence of growth factors.

What happens during S phase?

DNA synthesis or DNA replication.

What is produced when DNA replicates?

Two identical sister chromatids for each chromosome.

What happens during G2 phase?

The cell grows further and prepares for division.

What does the G2 checkpoint verify?

That DNA replication was completed properly.

What is euchromatin?

Loosely packed DNA that allows transcription and replication.

What is heterochromatin?

Tightly packed DNA that is generally less transcriptionally active.

Which form of chromatin is more transcriptionally active?

Euchromatin.

Which form of chromatin contributes to visible condensed chromosomes?

Heterochromatin.

What is the purpose of cell-cycle checkpoints?

To stop damaged or incompletely replicated cells from continuing through the cell cycle.

What are cyclins?

Regulatory proteins whose levels change throughout the cell cycle.

What do cyclins activate?

Cyclin-dependent kinases.

What do activated cyclin-dependent kinases do?

They phosphorylate proteins that promote progression through the cell cycle.

When are cyclin levels generally low?

During non-active phases.

When do cyclin levels increase?

When a particular stage of the cell cycle must be activated.

What is mitosis?

Cell division that produces two genetically identical daughter cells.

In which cells does mitosis occur?

Somatic cells.

What are the four phases of mitosis?

Prophase, metaphase, anaphase, and telophase.

What does PMAT stand for?

Prophase, metaphase, anaphase, and telophase.

What happens to the nuclear envelope during prophase?

It breaks down.

What happens to DNA during prophase?

It condenses into visible chromosomes.

What are sister chromatids?

Identical copies of a replicated chromosome.

Where are sister chromatids connected?

At the centromere.

What is a kinetochore?

A protein complex at the centromere where spindle microtubules attach.

What forms the mitotic spindle?

Microtubules organized by centrosomes.

What happens during metaphase?

Chromosomes align at the metaphase plate in the center of the cell.

What does the M checkpoint verify?

Correct chromosome alignment and spindle attachment.

What is the metaphase plate?

The center region of the cell where chromosomes align.

What happens during anaphase?

Sister chromatids separate and move toward opposite poles.

What cytoskeletal structure separates sister chromatids?

Microtubules.

What is a memory trick for anaphase?

Anaphase means chromatids move away.

What happens during telophase?

Nuclear envelopes and nucleoli reform around each chromosome set.

What process usually begins after telophase?

Cytokinesis.

What is cytokinesis?

Division of the cytoplasm into two cells.

What proteins form the contractile ring during cytokinesis?

Actin and myosin.

What is the cleavage furrow?

The indentation formed as the contractile ring pinches the cell.

What structure is divided during cytokinesis?

The cell membrane and cytoplasm.

What is the result of mitosis and cytokinesis?

Two separate genetically identical daughter cells.

What can unchecked mitosis cause?

Cancer.

Why do chemotherapy drugs cause side effects?

They may damage healthy cells that divide rapidly.

What normal cells often divide rapidly?

Skin cells, epithelial cells, hair-follicle cells, intestinal cells, and bone-marrow cells.

What is meiosis?

Cell division that produces haploid gametes.

What is the main function of meiosis?

Producing gametes for sexual reproduction.

How does meiosis promote evolution?

It creates genetic variation.

How many divisions occur in meiosis?

Two.

How many daughter cells are produced by meiosis?

Four.

Are the daughter cells produced by meiosis genetically identical?

No, they are genetically different.

Are meiotic daughter cells diploid or haploid?

Haploid.

Why is meiosis I called reductional division?

It reduces chromosome number from diploid to haploid.

What happens during synapsis?

Homologous chromosomes pair together.

When does synapsis occur?

During prophase I.

What is crossing over?

Exchange of genetic material between homologous chromosomes.

What does crossing over produce?

Recombinant chromosomes with new combinations of alleles.

What is a tetrad?

A paired set of homologous chromosomes containing four chromatids.

What lines up during metaphase I?

Homologous chromosome pairs or tetrads.

Where do homologous pairs line up during metaphase I?

At the equator of the cell.

What creates independent assortment?

The random orientation of homologous pairs during metaphase I.

What separates during anaphase I?

Homologous chromosomes.

Do sister chromatids separate during anaphase I?

No, they remain together.

What is produced after meiosis I?

Two haploid cells.

Why is meiosis II called equational division?

Sister chromatids separate without another reduction in chromosome number.

What lines up during metaphase II?

Individual chromosomes.

What separates during anaphase II?

Sister chromatids.

What is produced at the end of meiosis II?

Four genetically unique haploid cells.

What separates during mitosis?

Sister chromatids.

What separates during meiosis I?

Homologous chromosomes.

What separates during meiosis II?

Sister chromatids.

Where does mitosis occur?

In somatic cells.

Where does meiosis occur?

In germ cells.

How many divisions occur in mitosis?

One.

How many divisions occur in meiosis?

Two.

How many daughter cells does mitosis produce?

Two.

How many daughter cells does meiosis produce?

Four.

What is the chromosome number of mitotic daughter cells?

Diploid.

What is the chromosome number of meiotic daughter cells?

Haploid.

Are mitotic daughter cells genetically identical?

Yes.

Are meiotic daughter cells genetically identical?

No.

What lines up during metaphase of mitosis?

Individual replicated chromosomes.

What lines up during metaphase I of meiosis?

Homologous chromosome pairs.

What lines up during metaphase II of meiosis?

Individual replicated chromosomes.

Which process involves crossing over?

Meiosis I.

Which process produces cells for growth and repair?

Mitosis.

Which process produces sperm and egg cells?

Meiosis.