3.2.2 Cells - cell cycle and mitosis Flashcards
how do eukaryotic cells divide?
divide by mitosis or meiosis
how do prokaryotic cells divide?
prokaryotic cells replicate by binary fission
do viruses undergo cell division?
viruses do not undergo cell division as they are non-living
what is the process of binary fission?
binary fission involves the circular DNA and plasmids (if present) replicating
then the cytoplasm splitting to create two daughter cells
each daughter cell has one copy of the circular DNA, but a variable number of plasmid copies
where does viral replication occur?
inside the host cells and involves the injection of nucleic acid into the cell
what are the three main stages of the cell cycle?
interphase (G1, S, G2)
nuclear division (mitosis or meiosis)
cytokinesis
what happens during interphase?
the longest stage in the cell cycle
interphase is when the organelles duplicate, the cell grows and then DNA replicates
what does mitosis create?
creating two identical diploid cells
mitosis creates cells with identical DNA for growth and repair
what does meiosis create?
creating four genetically different haploid cells
meiosis creates gametes
what is cytokinesis?
the division of the cytoplasm to create new daughter cells
what are the 4 key stages of mitosis?
Prophase
Metaphase
Anaphase
Telophase
what happens during prophase of mitosis?
chromatin condenses into chromosomes and the nucleolus disappears
what happens during metaphase of mitosis?
chromosomes line up along the metaphase plate (imaginary plate)
what happens during anaphase of mitosis?
chromosomes break at centromeres, and sister chromatids move to opposite ends of the cell
what happens during telophase of mitosis and cytokinesis?
the chromosomes are now at each pole of the cell and become
longer and thinner again
The spindle fibers disintegrate, and the nucleus starts to reform.
The final stage in the cell cycle is when the cytoplasm splits in two to create the two new genetically identical cells
what is the equation for mitotic index?
the number of cells in mitosis
——————————————— x100
the total number of cells
What is the process by which eukaryotic cells divide?
Mitosis and meiosis
Mitosis results in two identical diploid cells, while meiosis results in four genetically different haploid cells.
What are the three key stages of the cell cycle?
Interphase, nuclear division, cytokinesis
Interphase includes G1, S, and G2 phases.
What occurs during the G1 phase of interphase?
Growth
This phase involves the cell growing and preparing for DNA synthesis.
What is the S phase of interphase responsible for?
DNA synthesis
During this phase, the cell replicates its DNA.
What happens in the G2 phase of interphase?
Growth and preparation for mitosis
This phase ensures the cell is ready for mitosis.
What is mitosis?
Nuclear division creating two identical diploid cells
Mitosis is essential for growth and repair.
What is meiosis?
Nuclear division creating four genetically different haploid cells
Meiosis is crucial for producing gametes.
What is cytokinesis?
Division of the cytoplasm to create new daughter cells
Cytokinesis occurs after nuclear division.
How do prokaryotic cells replicate?
Binary fission
This process involves the circular DNA and plasmids replicating before the cytoplasm splits.
What is binary fission?
A method of replication for prokaryotic cells
It involves the replication of circular DNA and plasmids and subsequent division of the cytoplasm.
Do viruses undergo cell division?
No
Viruses are non-living and replicate inside host cells by injecting nucleic acid.
What is the longest stage in the cell cycle?
Interphase
This stage includes organelle duplication, cell growth, and DNA replication.
What is mitosis?
Mitosis involves one round of division and results in two diploid, genetically identical daughter cells.
What are the main purposes of mitosis?
Mitosis is for growth and repair.
What is the first stage of mitosis?
Prophase
What happens during prophase?
The chromosomes condense and become visible, and the nuclear envelope disintegrates.
What is the role of centrioles in mitosis?
Centrioles separate and move to opposite poles of the cell, creating spindle fibres.
Which cells lack centrioles but have a spindle apparatus?
Plant cells
What is the second stage of mitosis?
Metaphase
What is the third stage of mitosis?
Anaphase
What is the fourth stage of mitosis?
Telophase
Fill in the blank: Mitosis results in two _______ cells.
diploid
Fill in the blank: During prophase, the nucleolus _______.
disappears
True or False: Mitosis results in genetically diverse daughter cells.
False
What structure attaches to the centromere and chromatids during mitosis?
Spindle apparatus
What happens to chromatin during prophase?
Chromatin condenses into chromosomes.
What is the significance of the spindle fibres?
They attach to the centromere and chromatids on the chromosome in later stages.
What happens to chromosomes during metaphase?
The chromosomes align along the equator of the cell
The spindle fibres released from the poles attach to the centromere and chromatid.
Define ‘equator’ in the context of cell division.
The imaginary plane where chromosomes line up during metaphase
Also referred to as the metaphase plate.
What is the role of the centromere?
It is the region where sister chromatids are joined and where spindle fibres attach
Essential for proper chromosome movement during cell division.
What are chromatids?
The individual strands of a chromosome that are joined at the centromere
Each chromatid is a copy of the chromosome.
Fill in the blank: During anaphase, the spindle fibres start to _______.
retract
What occurs to the centromere during anaphase?
It divides into two
This allows sister chromatids to move towards opposite poles.
What happens to chromatids during anaphase?
They are pulled to opposite poles and are now referred to as chromosomes
This separation is crucial for ensuring each daughter cell receives the correct number of chromosomes.
What energy source is required during anaphase?
ATP
ATP is provided by respiration in the mitochondria.
True or False: During metaphase, chromosomes are randomly distributed within the cell.
False
Chromosomes align specifically along the metaphase plate.
What is the function of spindle fibres in cell division?
To attach to centromeres and help separate chromatids during anaphase
They play a critical role in chromosome movement.
What is the final stage in the cell cycle?
Cytokinesis
Cytokinesis is when the cytoplasm splits in two to create two new genetically identical cells.
What happens to chromosomes during telophase?
Chromosomes unwind into chromatin
The chromosomes become longer and thinner again.
What reforms during telophase?
Nuclear membrane and nucleoli
The nuclear membrane reforms and nucleoli reappear.
What is the role of spindle fibres during telophase?
Disintegrate
Spindle fibres disintegrate as the cell prepares for cytokinesis.
What is the contractile ring made of?
Myosin II and actin filaments
These proteins contract to cleave the cell in two.
What is a cleavage furrow?
The indentation that forms during cytokinesis
It is where the cell membrane pinches in to separate the two new cells.
How is the mitotic index calculated?
Mitotic index = (Number of cells in mitosis × 100) / Total number of cells
It indicates the proportion of cells undergoing mitosis.
If 2 cells are in mitosis and 9 total cells are visible, what is the mitotic index?
22.2%
Calculation: (2 × 100) / 9 = 22.2%
True or False: The chromosomes become thicker during telophase.
False
The chromosomes become longer and thinner during this phase.
