Cell division Flashcards
What is a Cell cycle?
A series of precisely timed and carefully regulated stages of growth, DNA replication and division.
What are the two major phases in the cell cycle (mitosis)?
Interphase and the Mitotic Phase
What are the three stages within interphase
G1
S
G2
What processes take place in the stage of Interphase?
The cell prepares to divide.
DNA is replicated by semi- conservative replication.
There is now two copies of every chromosome.
The organelles are also replicated.
More ATP is produced to be used in cell division.
What processes take place in the stage of Prophase?
The nuclear envelope and the nucleolus break down.
Chromosomes are left floating in the cytoplasm.
The chromosomes coil more tightly and become shorter and fatter.
They can be seen under a light microscope.
Small protein bundles called centrioles move to opposite poles of the cell.
Microtubules form the mitotic spindle between the centrioles.
What processes take place in the stage of Metaphase?
The chromosomes line up along the mid-line of the cell.
In metaphase, the chromosomes are maximally condensed.
Centrioles attach the chromosomes to the spindle fibres on their centromere.
What processes take place in the stage of Anaphase?
The chromosomes break into two chromatids.
The sister chromatids separate at the centromere.
The spindles contract and pull the chromatids to each pole of the cell.
What processes take place in the stage of Telophase?
The chromatids reach the opposite poles and begin to decondense (unravel), becoming chromosomes again.
Nuclear envelopes form around the chromosomes so there are now two nuclei.
What is the Centromere?
The central region of a chromosome to which the microtubules of the spindle attach
What are Chromatids?
The two thread-like strands into which a chromosome divides longitudinally during cell division. Each contains a double helix of DNA.
What is Cytokinesis?
The division of the cytoplasm at the end of mitosis, bringing about the separation into two daughter cells.
What are Centriole?
They are a pair of small cylindrical organelles located near the nucleus and involved in the development of spindle fibres in cell division.
What is mitosis essential?
- Asexual reproduction by single celled organisms
- Reproduces cells that are identical in form and function
- Replace lost cells that have been damaged
How do single celled organisms introduce variation?
Mutations
Horizontal gene transfer (like transformation, conjugation, and transduction in bacteria),
Stochastic gene expression.
What is the order for the stages of meiosis?
- Interphase and prophase 1
2, Metaphase 1 - Anaphase 1 + Telophase1
- Cytokinesis
- Prophase 2 + Metaphase2
- Anaphase 2
- Telophase + Cytokinesis
What is the role of meiosis
Sexual Reproduction
Genetic Variation
Random fertilisation
Gamete Production
How does genetic variation occur in meisosis
Crossing over
Independent assortment
What is Crossing over?
exchange of genetic material between non sister chromatids of homologous chromosomes during meiosis 1
What is Independent assortment?
The chromosomes in a homologous pair are separated in meiosis I in a random formation to produce two genetically different daughter cells. The combination of chromosomes in the two daughter cells is random.
The process of separating chromosomes into random combinations is called independent assortment.
Independent assortment increases genetic variation.
How can a chromosome/ cell go through variation
Crossing over,
Independent assortment,
Fertilization
How many steps in meiosis?
8
Do both mitosis and meiosis go through cytokinesis
Yes
Does mitosis cross over?
No
Describe the functions and importance of mitosis with examples
Daughter cells are exact copies which means they have the same number as parent cell, meaning they are gentically stable.
It is for growth and repir, like replacing missing tissue, or wounds like skin healing, red blood cells are replaced by mitosis,
cancer is a form of mitosis which is going through uncontrolled division.
What happens in the G1 stage, during interphase?
Proteins produced
These proteins make organelles
Size of cell increases
What happens in the S stage, during interphase?
DNA is replicated in the nucleas
What happens in the G2 stage, during interphase?
Cell contiunes to incxrease in size
Energy store increases
DNA replication is checked for errors
What is the G0 stage?
When the cell leaves the cell cycle, this may be due to the cell differentiating, cell damage, or age.
What are the three checkpoints during mitosis?
G1 Checkpoint
G2 Checkpoint
M checkpoint
What does the G1 checkpoint check for?
Cell size
Nutrients
DNA damage
Growth factors
What does the G2 checkpoint check for?
Cell size
DNA replication
DNA damage
During Cytokinesis in animals, what forms to separate the cells?
Cleavage furrow forms around the middle of the cell.
The cell surface membrane is pulled in via the cytoskeleton until it is close enough to fuse around the middle forming two cells.
During Cytokinesis in plants, what forms to separate the cells?
Vesicles from the Golgi apparatus begin forming in the middle of the cell, these fuse with each other to form two separate membranes, then cell wall develops
What is the M checkpoint?
It ensures all chromosomes are properly attached to the spindle before the cell proceeds to anaphase.
