What is the cell cycle composed of?
- Interphase
- Mitosis
- Cytokinesis
The cell cycle allows cells to grow, prepare to divide, and then divide into two identical daughter cells.
During the cell cycle, a cell spends the majority of its lifetime in __________.
interphase
Interphase includes growth and preparation stages before mitosis.
What is the G0 phase?
A resting phase where the cell is not actively dividing
Mature cells like neurons may enter G0 and not participate in the cell cycle.
What occurs during the G1 phase of the cell cycle?
- Cell growth
- New protein synthesis
- Organelle development
A checkpoint ensures the necessary machinery for DNA synthesis is present.
What is the purpose of the S phase in the cell cycle?
DNA replication
This phase ensures each daughter cell receives an exact copy of genetic material.
What happens during G2 phase?
- Cell growth
- Preparation for mitosis
- Production of structures needed for cell division
A checkpoint at the end of G2 ensures readiness for mitosis.
What is the main function of mitosis?
Divides the nucleus and distributes DNA to daughter cells
Mitosis is the shortest phase of the cell cycle but involves significant activity.
During prophase, what happens to the DNA?
Condenses into chromosomes
Chromosomes become visible, and spindle fibers begin to form.
What occurs during metaphase?
Chromosomes line up at the metaphase plate
Centromeres attach to spindle fibers during this phase.
What happens in anaphase?
- Sister chromatids separate
- Chromosomes move to opposite ends of the cell
The cell begins to elongate as chromatids are pulled apart.
What is the outcome of telophase?
- Chromosomes uncoil
- Nuclear envelope forms around each set of chromosomes
In animal cells, the cytoplasm starts to pinch, while in plant cells, a cell plate forms.
What is cytokinesis?
The final stage that divides the cytoplasm into two daughter cells
In animals, the cytoplasm is pinched, while in plants, a cell plate forms.
At the end of one round of the cell cycle, how many daughter cells are produced?
Two identical daughter cells
These daughter cells are diploid (2n), containing two sets of chromosomes.
What type of cell division occurs in prokaryotic cells?
Binary fission
This is a simpler form of cell division resulting in two identical cells.
How often do cells divide?
Varies by cell type and organism
Skin cells constantly divide, while nerve and heart cells do not divide after maturity.
What can result from disruptions in the cell cycle?
Diseases, including cancer
Disruptions can lead to uncontrolled cell growth and tumors.
What is the role of the p53 gene?
Codes for a tumor-suppressing protein
Mutations in p53 can lead to loss of control over the cell cycle.
What are carcinogens?
Substances that mutate cells and can lead to cancer
Common carcinogens include tobacco smoke and radiation.
What are stem cells?
Undifferentiated cells with the potential to specialize
Sources include umbilical blood, bone marrow, and embryos.
What is cell differentiation?
The process by which cells become specialized
It is controlled by gene expression in somatic cells.
How do external factors affect cell differentiation?
They can disrupt gene expression
Triggers include temperature changes, injury, and exposure to chemicals.
In certain species of alligators, temperature determines the sex of the offspring. Eggs incubated below 30Β°C develop into __________.
females
Eggs incubated above 34Β°C typically develop into males.
