Unit 5: The Cell Cycle Flashcards
Every cell contains the same DNA in an individual but depending on how these instructions are expressed…
it will lead to a variety of cell types (such as blood cells, neurons, and muscle cells).
What is the cell cycle?
New cells are formed by
splitting of pre-existing cells
What type of cells does meiosis create?
Meiosis produces reproductive cells, called gametes.
What type of cells does mitosis create?
Mitosis produces all other cell types—somatic cells
Mitosis and meiosis are usually accompanied by __________.
cytokinesis
What is cytokinesis?
Division of cytoplasm into two daughter cells.
What is mitosis?
Genetic material is copied and divided equally between two
cells (cellular replication).
In mitosis, daughter cells are ___________ to the parent cell and to each other.
In mitosis, daughter cells are genetically identical to parent cell and to each other.
What does meiosis produce?
Produces daughter cells with only half of the hereditary material as
parent cell (four cells created).
For life to exist, cells must _________.
replicate
What are the three basic steps in cellular replication?
- Copying DNA
- Separating copies
- Dividing cytoplasm to create two complete cells.
What is chromatin?
Refers to a mixture of DNA and proteins that form the chromosomes.
What are chromosomes?
Refers to the condensed form of chromatin.
What are chromosomes made of?
Consists of double helix of DNA wrapped around proteins called histones. Consists of two sister chromatids.
What is a chromatid?
Each double-stranded DNA copy is called a
chromatid.
What are genes?
Region of DNA in chromosome. Codes for specific RNA to be transcribed which is then translated to a specific protein
Before cellular division, each chromosome is _________.
replicated
Before cellular division, chromosomes _________ into ___________.
Before cellular division, chromosomes condense into compact structures.
In mitosis, one _____ of each chromosome is distributed to each of the two ___________.
One copy of each chromosome is distributed to each of the two daughter cells.
Once mitosis begins, chromosomes are attached only at _________.
centromere
Cells can alternate between the dividing and non-dividing phases. What is the dividing phase and the nondividing phase?
- M (mitosis) phase- dividing phase
- Interphase- non-dividing phase
What is the M phase?
Dividing phase: cells in process of separating their chromosomes.
What is interphase?
Nondividing phase: chromosomes are uncoiled/uncondense. Cells are growing/preparing to divide.
What are the four phases of the cell cycle?
- Interphase consisting of G1, S, and G2.
- M phase consisting of mitosis/meiosis
What are gap phases?
During which no DNA
synthesis occurs.
What is the S phase?
Chromosome replication occurs only during interphase, specifically during the S phase.
What are two distinct events that occur during M phase?
- Mitosis
- Cytokinesis
What is cytokinesis?
Division of cytoplasm that forms two daughter cells.
When does mitosis begin?
Begins when chromatin condenses.
What do sister chromatids do during mitosis?
During mitosis, two sister chromatids separate to form independent daughter chromosomes
How many copies does each daughter cell get during mitosis?
One copy of each
chromosome goes to each of the two daughter cells.
What are the five subphases of mitosis?
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
What is prophase?
Chromosomes condense, and spindle apparatus begins to form.
What is prometaphase?
Nuclear envelop breaks down, and microtubules contact chromosomes at kinetochores.
What is metaphase?
Chromosomes migrate to middle of cell.
What is anaphase?
Sister chromatids separate into daughter chromosomes, which are pulled to opposite poles of spindle apparatus.
What is telophase?
Nuclear envelopes reforms, chromosomes de-condense.
What is cytokinesis?
Actin-myosin ring causes the plasma membrane to being pinching in. Two daughter cells form.
What are kinetochores?
The structures on sister chromatids where microtubules attach.
What are centrosome?
The microtubule-organizing center in animals and certain plants and fungi. Each pole in the spindle apparatus is a centrosome.
What are micotubules?
Cytoskeletal filaments that form the spindle apparatus.
How does bacteria divide?
Bacteria divide via binary fission.
What is binary fission similar to?
Process similar to eukaryotic M phase.
What are the three steps to binary fission?
- Bacterial chromosomes are replicated.
- Protein filaments attach to replicated bacterial chromosomes.
- Filaments pull chromosomes apart.
What affects cell-cycle length?
Mostly due to variation in length of G1 phase.
What phase do rapidly dividing cells eliminate?
Rapidly dividing cells essentially eliminate G1
phase.
What phase do nondividing cells get stuck in?
Nondividing cells get permanently stuck in
G1 phase.
What is the arrested state?
Arrested state is called the G0 state.
Variations in cell-cycle length suggest that cell
cycle is _________.
regulated
What are cell-cycle checkpoints?
Critical points in cell cycle that are regulated.
What are regulatory molecules?
Regulatory molecules at each checkpoint allow cell to “decide” whether to proceed with division
What happens if regulatory molecules are defective?
If these regulatory molecules are defective, checkpoint may fail. Cells that divide without control may form a tumor.
What is the G1 checkpoint?
The cell growth checkpoint. Establishes if cell will continue through cell cycle and divide.
What is the G2 checkpoint?
DNA synthesis checkpoint.
What is the G3 checkpoint?
Mitosis checkpoint
What are the four factors that affect passage through G1 checkpoint?
- Size
- Availability of nutrients
- Social signals from other cells
- Damage to DNA
What is the p53 tumor suppressor?
If DNA is physically damaged, p53 activates proteins that pause cell cycle until damage can be repaired.
What is apoptosis?
If cell can’t be repaired, p53 initiates apoptosis, programmed cell death.
What happens if the p53 gene is damaged?
Damage to the p53 gene can lead to uncontrolled cell division.
Where does the G2 checkpoint occur?
Second checkpoint occurs after S phase.
What is the G2 checkpoint?
If chromosome replication has not proceeded properly or if DNA is damaged, cells remain in G2 phase.
How many M phase checkpoints are there? Where do they occur?
Final two checkpoints occur during Mitosis. One occurs between Metaphase and Anaphase the other between anaphase and telophase.
What does the mitosis checkpoint between metaphase and anaphase check for?
Ensures that sister chromatids do not split until all kinetochores are attached to the spindle apparatus
What does the mitosis checkpoint between anaphase and telophase check for?
Ensures that chromosomes have fully separated.
