Biology Chapter 12: The Cell Cycle

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Questions and Answers

What is the likely evolutionary relationship between mitosis and binary fission?

Mitosis evolved independently from binary fission.

Binary fission is a modified form of mitosis.

Mitosis and binary fission are completely unrelated processes.

Mitosis likely evolved from binary fission. (correct)

In which type of organisms do most eukaryotes exhibit cell division characteristics?

Organisms without nuclear envelopes.

Organisms with fragmented nuclear envelopes. (correct)

Organisms with dual nuclei.

Organisms with intact nuclear envelopes.

What role do chemical signals in the cytoplasm play in the cell cycle?

They regulate the phases of the cell cycle. (correct)

They inhibit the cell cycle from proceeding.

They destroy cells that are in the wrong phase.

They have no effect on cell division.

What was the result when a cell in the S phase was fused with a cell in the G1 phase?

The G1 nucleus entered the S phase and DNA synthesis began. Signup and view all the answers

Which type of cell division shows characteristics intermediate between binary fission and mitosis?

Dinoflagellates and diatoms. Signup and view all the answers

Where does evidence supporting the hypothesis of cytoplasmic signals come from?

Experiments involving cultured mammalian cells at different cell cycle phases. Signup and view all the answers

What happens when a cell in the M phase is fused with a cell in G1 phase?

The G1 nucleus begins mitosis. Signup and view all the answers

What is true regarding the frequency of cell division among different types of cells?

The frequency varies among different cell types. Signup and view all the answers

What distinguishes living organisms from nonliving matter?

The ability to reproduce Signup and view all the answers

During which phase of the cell cycle are chromosomes duplicated?

S phase Signup and view all the answers

What is the role of the mitotic spindle during mitosis?

To control chromosome movement Signup and view all the answers

What type of cells undergo meiosis?

Gametes Signup and view all the answers

What is the primary purpose of cytokinesis?

To divide the cytoplasm Signup and view all the answers

What stage of mitosis is characterized by the alignment of chromosomes at the equatorial plate?

Metaphase Signup and view all the answers

What is the role of sister chromatids during mitosis?

They separate and move to opposite poles Signup and view all the answers

Which of the following describes the structure of a chromosome during mitosis?

Two identical DNA molecules joined at the centromere Signup and view all the answers

In what way do prokaryotic cells reproduce?

Through binary fission Signup and view all the answers

What causes the cleavage furrow in animal cells during cytokinesis?

Contractile ring of microfilaments Signup and view all the answers

What is the G1 phase of the cell cycle primarily involved with?

Cell growth and metabolic activities Signup and view all the answers

What is true about gametes in regards to chromosome number?

They have half the number of chromosomes as somatic cells Signup and view all the answers

Which phase of mitosis comes immediately after metaphase?

Anaphase Signup and view all the answers

What structure forms during cytokinesis in plant cells?

Cell plate Signup and view all the answers

What happens if a cell does not receive a go-ahead signal at the G1 checkpoint?

It exits the cell cycle and enters the G0 phase. Signup and view all the answers

Which of the following proteins fluctuate and are key regulators of the cell cycle?

Cyclins and cyclin-dependent kinases Signup and view all the answers

What is the role of MPF (maturation-promoting factor) in the cell cycle?

It triggers a cell’s passage past the G2 checkpoint into the M phase. Signup and view all the answers

Which statement accurately reflects the G0 phase?

Cells can re-enter the cell cycle when conditions are favorable. Signup and view all the answers

What type of signal can kinetochores send to delay anaphase?

Molecular signals Signup and view all the answers

How do cancer cells typically respond to growth factors?

They do not need growth factors to grow and can produce their own. Signup and view all the answers

What type of tumor is characterized by cells that stay localized and do not spread?

Benign tumor Signup and view all the answers

In what way does anchorage dependence affect normal animal cells?

They must be attached to a substratum to divide. Signup and view all the answers

What is density-dependent inhibition?

A mechanism where crowded cells stop dividing. Signup and view all the answers

During which phase do cyclins accumulate in preparation for their subsequent role?

G2 phase Signup and view all the answers

What characterizes a malignant tumor as opposed to a benign tumor?

Malignant tumors invade surrounding tissues and may metastasize. Signup and view all the answers

What type of checkpoint is considered the most critical for many cells?

G1 checkpoint Signup and view all the answers

What phase is characterized by chromatin condensation even before chromosome duplication?

M phase Signup and view all the answers

Study Notes

Chapter 12: The Cell Cycle

Cell division is essential for life
Organisms reproduce by cell division
Cell division distinguishes living from nonliving matter.
In unicellular organisms, cell division creates new organisms.
Multicellular organisms use cell division for development, growth, and repair
Cell division is the core functionality of the cell cycle.

Overview: The Key Roles of Cell Division

The ability to reproduce distinguishes living things from nonliving matter.
Life's continuity depends on cell reproduction (cell division)

Cellular Organization of the Genetic Material

A cell's genome is all the DNA within a cell.
Some prokaryotic genomes consist of a single DNA molecule.
Eukaryotic genomes contain multiple DNA molecules.
DNA in a cell is organized into chromosomes.

Distribution of Chromosomes During Eukaryotic Cell Division

DNA replicates and condenses before cell division.
Each duplicated chromosome has two sister chromatids.
Sister chromatids separate during cell division.
The centromere is the narrow "waist" of a duplicated chromosome
The centromere holds the sister chromatids together.

Eukaryotic Cell Division

Eukaryotic cell division includes mitosis (nuclear division) and cytokinesis (cytoplasmic division).
The cell cycle includes the mitotic (M phase) and interphase.

Phases of the Cell Cycle

Interphase, which is approximately 90% of the cell cycle, includes G1, S, and G2 phases.
Cell growth happens in the G1, S, and G2 phases.
DNA replication occurs during the S phase.

Mitosis

Mitosis consists of five stages: prophase, prometaphase, metaphase, anaphase, and telophase.
Cytokinesis begins during late telophase.

The Mitotic Spindle: A Closer Look

The mitotic spindle is a cytoskeletal structure made of microtubules.
The centrosome is the microtubule organizing center.
During prophase, spindle microtubules assemble in the centrosome.
Centrosomes move to opposite poles of the cell.
An aster is a radial array of short microtubules extending from each centrosome.

Cytokinesis: A Closer Look

Cytokinesis divides the cytoplasm.
In animal cells, a cleavage furrow forms.
In plant cells, a cell plate forms.
Binary fission is the type of cell division in prokaryotes.

The Cell Cycle Control System

Cell cycle events are regulated by a molecular control system.
The frequency of cell division varies with the cell type.
Internal and external controls regulate the cycle.
The system involves checkpoints where the cell cycle stops until the proper signal is received.
The G₁ checkpoint is often the most critical.
If the cell gets a go-ahead signal at the G₁ checkpoint, it will complete the rest of the cycle. Otherwise, cells enter a nondividing state called G₀.
The cell cycle clock has Cyclins and cyclin-dependent kinases (Cdks).
MPF is a type of cyclin-Cdk complex.
Some internal signals include the attachment of kinetochores to microtubules or growth factors.
Some external signals include density-dependent inhibition and anchorage dependence.
- Cancer cells lack density-dependent inhibition and anchorage dependence.
- Cancer cells do not respond normally to the body's control mechanisms.
- Cancer cells may not need growth factors to grow and divide.
- Cancer cells may have an abnormal cell cycle control system.
Normal cells are transformed into cancer cells.
Benign tumors stay in one place; malignant tumors can metastasize.

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Description

This quiz explores the fundamental concepts of cell division and its critical role in the life cycle of organisms. It covers the importance of cell reproduction, the organization of genetic material, and the process of chromosome distribution during cell division. Test your knowledge on how cell division impacts both unicellular and multicellular life forms.