Cell Cycle and Cellular Reproduction

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the diploid number of chromosomes in humans?

46 (correct)

During which phase of mitosis do the chromatids become visible after replication?

Anaphase

Prometaphase

Early Prophase (correct)

Metaphase

In which phase of mitosis are the centromeres of duplicated chromosomes aligned at the metaphase plate?

Prophase

Telophase

Anaphase

Metaphase (correct)

What structure organizes the mitotic spindle in animal cells?

Centrosome Signup and view all the answers

What connects each sister chromatid to the spindle fibers during cell division?

Kinetochore Signup and view all the answers

What is the primary role of caspases in the process of apoptosis?

To trigger programmed cell death. Signup and view all the answers

Which of the following best describes the relationship between apoptosis and cell division?

They are opposing processes. Signup and view all the answers

What characterizes euchromatin, compared to heterochromatin?

Less compacted and transcriptionally active. Signup and view all the answers

What role do tumor suppressor genes play in cell cycle regulation?

They help repair DNA and regulate the cell cycle. Signup and view all the answers

During mitosis, what happens to the chromatin?

It condenses into distinct chromosomes. Signup and view all the answers

How do oncogenes contribute to cancer development?

By mimicking growth factors and stimulating excessive cell division. Signup and view all the answers

Which statement accurately reflects the importance of the cell cycle regulation?

Regulation prevents uncontrolled cell division and maintains tissue homeostasis. Signup and view all the answers

What type of DNA structure is formed by DNA wrapped around histones?

Nucleosome Signup and view all the answers

What role does the protein p53 play at the G1 checkpoint?

It initiates apoptosis if DNA damage cannot be repaired. Signup and view all the answers

What is a characteristic of heterochromatin?

It is compact and rarely transcribed. Signup and view all the answers

Which of the following checkpoints primarily monitors nutrient availability?

G1 checkpoint Signup and view all the answers

What kind of genetic mutations are often associated with cancer development?

Mutations that lead to the permanent activation of oncogenes. Signup and view all the answers

What happens to the cell cycle if cyclins are absent?

The cell cycle stops at checkpoints. Signup and view all the answers

Which environmental factor is known to increase the risk of genetic mutations leading to cancer?

Exposure to certain chemicals and radiation. Signup and view all the answers

What does the spindle assembly checkpoint ensure during mitosis?

Chromosomes are properly aligned. Signup and view all the answers

What effect does apoptosis have on the number of somatic cells?

It decreases the number of cells. Signup and view all the answers

Which checkpoint is responsible for verifying the completion and integrity of DNA replication?

G2 checkpoint Signup and view all the answers

Which phase of the cell cycle is primarily affected by the presence of growth factors?

G1 Stage, where the cell grows and doubles organelles. Signup and view all the answers

Which component of the cell division process follows mitosis?

Cytokinesis Signup and view all the answers

What is the primary outcome of the mitotic stage of the cell cycle?

The division of a cell into two genetically identical daughter cells. Signup and view all the answers

What is the likely outcome if significant DNA damage is detected at the G1 checkpoint?

The cell undergoes apoptosis. Signup and view all the answers

Which family of proteins plays a crucial role in regulating the cell cycle?

Cyclins that fluctuate in concentration during the cell cycle. Signup and view all the answers

How do environmental factors influence cancer development?

They can induce genetic mutations. Signup and view all the answers

Which protein is involved in checking for proper alignment of chromosomes during mitosis?

Spindle Checkpoint Proteins Signup and view all the answers

How does retinoblastoma (RB) contribute to cell cycle regulation?

It regulates nutrient availability. Signup and view all the answers

What is the consequence of failing to pass the G2 checkpoint?

The cell may enter apoptosis. Signup and view all the answers

What initiates the cell to become committed to divide during the cell cycle?

Presence of growth signals and nutrients Signup and view all the answers

Which of the following statements about cell cycle checkpoints is true?

Checkpoints ensure proper progression through the cell cycle. Signup and view all the answers

During which phase of mitosis do sister chromatids separate and move towards opposite poles?

Anaphase Signup and view all the answers

What structure forms between two daughter plant cells during cytokinesis?

Cell plate Signup and view all the answers

What is the primary outcome of telophase in mitosis?

Nuclear envelopes reappear Signup and view all the answers

Which of the following is a key difference in mitosis between animal and plant cells?

Formation of a cell plate in plant cells Signup and view all the answers

What happens to chromosomes during telophase?

They reform into chromatin Signup and view all the answers

What is the main purpose of the G1 stage in the cell cycle?

Cell doubles its organelles Signup and view all the answers

Which of the following correctly describes the S stage of the cell cycle?

DNA replication and chromosome duplication occur Signup and view all the answers

What defines the mitotic stage of the cell cycle?

Division of the cytoplasm and nucleus Signup and view all the answers

In which stage of the cell cycle do sister chromatids become genetically identical?

S Stage Signup and view all the answers

What role do cyclins play in the cell cycle?

They control the timing of the cycle Signup and view all the answers

What occurs during the G2 stage of the cell cycle?

Cell synthesizes proteins for division Signup and view all the answers

Which statement about the role of growth factors in the cell cycle is accurate?

Growth factors promote cell division by interacting with the plasma membrane Signup and view all the answers

What is the consequence if the cell fails to progress through the G1 checkpoint?

Cell enters a non-dividing state (G0) Signup and view all the answers

What happens to a cell when it loses contact with neighboring cells during apoptosis?

It begins to round up and fragment. Signup and view all the answers

Why is mitosis important for cellular function?

It allows for the equal distribution of chromosomes to daughter cells. Signup and view all the answers

What defines the term 'nucleosome' in the context of chromatin?

DNA wrapped around eight histones. Signup and view all the answers

Which form of chromatin is more readily transcribed by RNA polymerase?

Euchromatin Signup and view all the answers

What is the relationship between apoptosis and mitosis?

Apoptosis decreases cell numbers while mitosis increases them. Signup and view all the answers

What is one of the roles of caspases in cellular processes?

To initiate programmed cell death. Signup and view all the answers

What process follows mitosis in eukaryotic cell division?

Cytokinesis Signup and view all the answers

What characteristic of heterochromatin is significant?

It is more compacted and less transcriptionally active. Signup and view all the answers

What ensures that chromosomes are properly aligned before mitosis proceeds?

Spindle assembly checkpoint Signup and view all the answers

What occurs to chromatin before mitosis begins?

It condenses into distinctly visible chromosomes. Signup and view all the answers

What is the primary function of the p53 protein at the G1 checkpoint?

To repair DNA damage or initiate apoptosis Signup and view all the answers

Which checkpoint is crucial for assessing whether DNA replication was completed successfully?

G2 checkpoint Signup and view all the answers

Which statement accurately describes the role of kinetochores during mitosis?

Kinetochores connect sister chromatids to spindle fibers. Signup and view all the answers

If apoptosis is initiated at the G1 checkpoint, what is the likely reason?

DNA damage cannot be repaired Signup and view all the answers

What are specific cyclins required for during the cell cycle?

Advancing the cell from one stage to the next Signup and view all the answers

What is the primary function of centrosomes in animal cells during mitosis?

They organize the mitotic spindle. Signup and view all the answers

During which phase of mitosis are spindle fibers fully formed and chromosomes lined up at the center of the spindle?

Metaphase Signup and view all the answers

What role does retinoblastoma (RB) protein play in the cell cycle?

Assessing nutrient availability Signup and view all the answers

What occurs during the prometaphase of mitosis?

The kinetochore attaches to spindle fibers. Signup and view all the answers

What is the consequence if the M checkpoint fails during mitosis?

The cell cycle progresses without checking chromosome alignment Signup and view all the answers

What change in the cell occurs during early prophase?

Chromosomes become visible and chromatin condenses. Signup and view all the answers

Which checkpoint serves as the main regulator of the cell cycle?

G1 checkpoint Signup and view all the answers

How many stages are there in the process of mitosis?

5 Signup and view all the answers

Which of the following is primarily checked during the G2 checkpoint?

DNA replication integrity Signup and view all the answers

During which phase is a cell committed to divide, assuming there are adequate nutrients and growth signals?

G1 phase Signup and view all the answers

Which of the following best describes the events occurring at the anaphase stage of mitosis?

Sister chromatids separate and move towards opposite poles. Signup and view all the answers

What happens at the M checkpoint in the cell cycle?

Chromosome alignment and attachment to the spindle are checked Signup and view all the answers

What describes the haploid number of chromosomes?

One copy of each chromosome pair. Signup and view all the answers

What defines the role of the spindle fibers during mitosis?

They facilitate the separation of sister chromatids. Signup and view all the answers

What happens during telophase?

The spindle fibers disassemble and the nuclear envelope re-forms. Signup and view all the answers

Study Notes

Overview of Cell Cycle and Cellular Reproduction

The cell cycle is a series of events that lead to cell division, creating two genetically identical daughter cells.
Eukaryotic cell division involves mitosis (nuclear division) and cytokinesis (cytoplasm division).
The cell cycle is roughly 20 hours in mammals.

Interphase

The longest part of the cell cycle (about 90% of the cycle).
Divided into three stages:
- G₁ (Gap 1): Cell growth, organelle duplication (mitochondria and ribosomes). Nerve and muscle cells remain in G₀.
- S (Synthesis): DNA replication, synthesizing proteins associated with DNA. Each chromosome duplicates into two identical chromatids.
- G₂ (Gap 2): Cell synthesizes proteins necessary for cell division (e.g., microtubule proteins).

Sister Chromatids

Chromosomes duplicated during the S phase consist of two identical chromatids.
Attached at the centromere, forming an X shape.
Essential for accurate chromosome segregation during mitosis.

Mitotic Stage

Follows interphase.
Mitosis: Division of the nucleus, creating two genetically identical nuclei.
Cytokinesis: Division of the cytoplasm, forming two separate daughter cells.
Results in two genetically identical daughter cells.

Control of the Cell Cycle

Controlled by internal and external signals.
External signals: Growth factors, signaling proteins received at the plasma membrane.
Internal signals: Cyclins, proteins that increase and decrease throughout the cell cycle. Specific cyclins are needed for the cell to progress from one stage to the next. Without cyclins the cell cycle stops at checkpoints (G₁, M, or G₂).

Cell Cycle Checkpoints

Critical control points to ensure accurate DNA replication and cell division.
- G₁ checkpoint: p53 checks for DNA damage, initiating DNA repair or apoptosis if repair isn't possible. RB checks for nutrient availability.
- G₂ checkpoint: Checks if DNA replication was completed correctly or if DNA is damaged.
- M checkpoint: Monitors proper alignment and attachment of chromosomes to the mitotic spindle.

Apoptosis

Programmed cell death caused by enzymes called caspases.
A natural process to eliminate abnormal or damaged cells.
Controlled by inhibitors, but can be unleashed by external or internal signals.
Opposes cell division (which increases somatic cell number), keeping the cell count appropriate.

Eukaryotic Chromosomes

Consist of a single DNA molecule condensed by histone proteins (DNA + histones = chromatin).
Nucleosomes: DNA wrapped around histone proteins.
- Nucleosomes are joined by "linker" DNA.
Euchromatin: Active chromatin, able to be transcribed.
Heterochromatin: More compact, inactive chromatin.

Mitosis and Cytokinesis in Eukaryotic Cells.

Mitotic stages involve: prophase, prometaphase, metaphase, anaphase, telophase.
Centrioles move to opposite poles, forming the mitotic spindle (microtubule fibers).
Each fiber is a cylindrical bundle of microtubules.
The spindle will allow chromosomes to move to opposite poles, so each new cell has a full set of chromosomes.

Mitosis in Animal Cells, Plant cells, and Prokaryotes

Animal cells: Utilize cleavage furrow (contractile ring of actin filaments) during cytokinesis, a process that constricts and separates the daughter cells, while plant cells produce a cell plate that separates the daughter cells.
Prokaryotes: Binary fission is the process where DNA replication results in two complete chromosomes that will be replicated and the cell divides into two daughter cells.
- The chromosome is a ring of DNA.
- Chromosome replicates into two rings.
- The rings attach to the cell membrane.

The Cell Cycle and Cancer

Cancer results from abnormal cell growth, developing uncontrolled cell division, caused by mutations in genes regulating the cell cycle.
Abnormal cell growth is called a tumor.
- Benign tumors are not cancerous and encapsulated.
- Malignant tumors are cancerous and readily invade neighboring tissue and spread (metastasis).
Carcinogenesis: Gradual cancer development, can take years.

Characteristics of Cancer Cells

Lack differentiation (not specialized).
Immortal (enter the cell cycle repeatedly).
Abnormal nuclei and chromosomes with extra copies of genetic material.
Do not undergo apoptosis.
No contact inhibition (tumors form).
Undergo metastasis (spread) and angiogenesis (formation of new blood vessels).

Cancer Cells vs. Normal Cells (table)

Compare and contrast characteristics between cancer and normal cells.

Progression of Cancer

Tumors grow rapidly, requiring more blood vessels for oxygen and nutrients.
Cancer in situ (tumor remains at the origin).
Metastasis: Cancer cells invade lymphatic and blood vessels to spread throughout the body.

The Origin of Cancer

Normal cell growth and tissue maintenance balance between signals promoting and inhibiting cell division.
Two mutated genes:
- Proto-oncogenes (become oncogenes): Genes that promote the cell cycle. Mutations lead to increased cell division.
- Tumor suppressor genes (inactivation): Genes that inhibit cell cycle and/or promote apoptosis. Mutations result in loss of inhibition or increased cell growth.

Proto-oncogenes Become Oncogenes

Proto-oncogenes are stimulatory pathway components like receptors and signaling molecules.
Mutations can produce an abnormal protein.
Cancer arises from uncontrolled high levels of a normal product.

Tumor Suppressor Genes Become Inactive

Mutations cause the cell cycle to accelerate.
Examples are the RB and p53 genes.
RB gene mutations associated with retinoblastoma (inherited condition).
p53 gene activates other cell cycle proteins.

Causes of Cancer

External and hereditary influences can also contribute to cancer, such as radiation, heredity, pesticides, herbicides, viruses, and various other influences.

The Cell Cycle and Telomeres

Telomeres: Protective caps at the ends of chromosomes.
Telomeres shorten after each cell division, causing a cell to no longer divide.
Telomerase: Enzyme that maintains telomere length, and cancer cell-telomerase enables continuous cell division.
Mutations in telomerase cause cancer cells maintain continuous cell division.

Prokaryotic Cell Division (Binary Fission)

Prokaryotes reproduce asexually through binary fission.
Chromosome is a ring of DNA.
Chromosomes replicate into two separate rings.
Rings attach to the membrane. The membrane grows inward, separating the two daughter cells.

Comparing Prokaryotes and Eukaryotes

Prokaryotic division: Binary fission, with identical daughter cells; Eukaryotic division (mitosis), allows more complex cells growth and repair.

Table 9.3 Functions of Cell Division

Describe division types for various organisms.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz covers the cell cycle and the process of cellular reproduction, focusing on eukaryotic cell division through mitosis and cytokinesis. Key phases include interphase, sister chromatids, and chromosomal behavior during division. Test your understanding of these fundamental biological processes!