40 Questions
During which phase of the cell cycle does growth occur?
G1
What is the average duration of the cell cycle for a typical mammalian cell?
24 hours
Which phase of mitosis is characterized by the alignment of chromosomes along the metaphase plate?
Metaphase
What is the key event that marks the beginning of anaphase?
Splitting of centromeres
What is the process by which the cell divides into equal halves called?
Cytokinesis
What is the role of actin filaments in animal cell cytokinesis?
Formation of a cleavage furrow
Which protein has a structure similar to eukaryotic tubulin?
FtsZ
What is the role of FtsZ in bacterial division compared to the role of tubulin in mitosis in eukaryotes?
FtsZ is involved in cell division while tubulin is involved in cell growth
How many chromosomes do eukaryotes typically have in their body (somatic) cells?
46
What is a karyotype?
A particular array of chromosomes in an individual organism
What is the primary component of chromosomes?
DNA
What is the role of histone H1 in chromatin structure?
It interacts with linker DNA
Which process do bacteria use to divide?
Binary fission
What is the structure that forms to divide a bacterial cell into two cells?
Septum
Which protein is involved in the formation of a septum during binary fission?
FtsZ
How many directions does bacterial chromosome replication proceed during binary fission?
Two
Which term describes the process of chromosome segregation and division of cytoplasmic contents in eukaryotic cells?
Mitosis
What is the main difference between bacterial cell division and eukaryotic cell division?
Bacterial cells have a sexual life cycle, while eukaryotic cells reproduce clonally
Which of the following is a key function of checkpoints in the cell cycle?
To respond to internal and external signals
What is the role of cyclins in the cell cycle?
To control the activity of cyclin-dependent kinases
What is the function of the G1/S checkpoint in the cell cycle?
To replicate genetic material
What is the role of MPF (mitosis-promoting factor) in the cell cycle?
To induce cell division
What is the function of the anaphase-promoting complex (APC) in the cell cycle?
To trigger anaphase
What are proto-oncogenes?
Genes that encode receptors for growth factors
Which type of gene requires both copies to lose function for the cancerous phenotype to develop?
Tumor-suppressor gene
What is the role of the Rb protein in signal integration?
To bind important regulatory proteins
What is the function of the p53 protein in cell division?
To direct the cell to kill itself
What has whole-genome sequencing revealed about tumors?
Tumors have variation in chromosomal alterations
Which categories of genes are associated with increasing mutations or changes in gene expression in a tumor?
DNA repair, mRNA splicing, and chromosome architecture genes
What can be combined with a patient's genotype to determine effective cancer treatment?
The spectrum of mutated genes in the patient's tumor
Which type of gene requires both copies to lose function for the cancerous phenotype to develop?
Tumor-suppressor gene
What is the role of the Rb protein in signal integration?
To integrate signals from growth factors
What is the function of the p53 protein in cell division?
To halt cell division and stimulate repair enzymes in the presence of DNA damage
What is the role of actin filaments in animal cell cytokinesis?
To form a contractile ring that constricts the cell
What is the average duration of the cell cycle for a typical mammalian cell?
24 hours
What is the main difference between bacterial cell division and eukaryotic cell division?
Bacterial cell division does not involve mitosis
What is the primary component of chromosomes?
Nucleic acids
What is the function of the G1/S checkpoint in the cell cycle?
To check for DNA damage before entering S phase
What can be combined with a patient's genotype to determine effective cancer treatment?
Whole-genome sequencing
What is the role of MPF (mitosis-promoting factor) in the cell cycle?
To promote entry into mitosis
Study Notes
Bacterial Cell Division
- Bacteria divide by binary fission, a process that does not involve a sexual life cycle.
- Reproduction is clonal, meaning that the new cell is a genetic replica of the parent cell.
- The single, circular bacterial chromosome is replicated, and the new chromosomes are partitioned to opposite ends of the cell.
- A septum forms to divide the cell into two daughter cells.
Eukaryotic Chromosomes
- Eukaryotes typically have 10 to 50 chromosomes in their body cells, with humans having 46 chromosomes in 23 nearly identical pairs.
- Chromosomes are composed of chromatin, a complex of DNA and protein.
- DNA is organized into nucleosomes, which are coiled to form chromatin fibres.
- Chromatin is organized into territories, which contain individual chromosomes, and are further divided into compartments.
Eukaryotic Cell Cycle
- The cell cycle consists of four stages: G1, S, G2, and M.
- G1 is the primary growth phase, during which the cell grows and prepares for DNA replication.
- S is the synthesis phase, during which DNA replication occurs.
- G2 is the preparation phase, during which the cell prepares for mitosis.
- M is the mitosis phase, during which the cell divides into two daughter cells.
Mitosis
- Mitosis is divided into five stages: prophase, prometaphase, metaphase, anaphase, and telophase.
- Prophase: individual condensed chromosomes become visible, and the spindle apparatus assembles.
- Prometaphase: microtubules attach to kinetochores, and chromosomes begin to move to the center of the cell.
- Metaphase: chromosomes align along the metaphase plate.
- Anaphase: sister chromatids separate and move to opposite poles.
- Telophase: the spindle apparatus disassembles, and nuclear envelope forms around each set of sister chromatids.
Control of the Cell Cycle
- The cell cycle has two irreversible points: replication of genetic material and separation of sister chromatids.
- The cell cycle can be put on hold at specific checkpoints, allowing the cell to respond to internal and external signals.
- Cell cycle control factors include MPF (maturation-promoting factor), cyclins, and cdk2.
Cell Cycle Control Factors
- MPF is composed of a cyclin and cdk2, and is responsible for driving the cell cycle forward.
- Cyclins are proteins that are produced in synchrony with the cell cycle.
- cdk2 is a kinase that is critical for passing the boundary between the G1 and S phases.
- The cell cycle is controlled by a series of checkpoints, including the G1/S, G2/M, and spindle checkpoints.
Cancer
- Cancer is a result of unrestrained, uncontrolled growth of cells, often due to failure of cell cycle control.
- Two types of genes can disturb the cell cycle when mutated: tumor-suppressor genes and proto-oncogenes.
- Proto-oncogenes can become oncogenes when mutated, leading to uncontrolled cell growth.
Test your knowledge on the duration of cell cycles with this quiz. Explore the varying time it takes for different cells to complete their cycles, from fruit fly embryos to mature cells. Learn about the growth phases and resting phase of cells, and discover the fascinating differences in cell cycle lengths.
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