Cellula Flashcards
Which is the longest stage in the cell cycle?
Interphase, formed by stage G1 (cell growth), stage S (DNA replication) and stage G2 (organelles and proteins)
What two organelles are broken down during prophase ?
The membrane envelope and the nucleolus
What happens in late prophase ?
The nuclear envelope (and nucleolus) break down releasing the condensed DNA in the cytoplasm
Why isn’t DNA visible during interphase ?
Because it is in it’s unbound state (the only one in which it is able to work), during prophase it will get condensed in order for the newly shaped sister chromatids to be divided properly
What differentiates anaphase and metaphase ?
In metaphase the sister chromatids are positioned in a line at the equator. In anaphase they have already been pulled by the spindle fiber, split at the centromere and are traveling in opposite direction through the cytoplasm to the poles.
What is the role of centrioles in mitosis?
After having moved to the poles they produce spindle fibers that attach at the centromeres of the sister chromatids
Why is mitosis important?
it allows:
- for the dead or damaged cells to get changed with new ones (helping to repair tissues or undergo the growth of the organism)
- asexual reproduction
What are the benefits of asexual reproduction?
It is helpful as another parent is not needed for this type of reproduction (so it can be done everywhere), is quick and permits quick colonisation of a new area
What are the downfalls of asexual reproduction?
The new offspring has the exact same DNA as their parent, meaning that any type of evolution or adaptation to the surroundings does not occur ( this could potentially lead to the extinction of a whole group as no individual is able to adapt and everyone is susceptible to the same threats)
what are the stages of cell division?
Interphase (G1, S, G2)
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
which is the shortest stage in mitosis?
anaphase, as it is involved only in the separation of the sister chromatids
what happens in prophase (general)?
-DNA previously replicated is condensed from its unbound state into sister chromatids attached at the centromere
-Centrioles move from the region close to the centre to the opposite ends of the cells now called poles
-Centrioles start producing spindle fibres
-The nuclear envelope breaks down alongside the nucleolus and the sister chromatids are freed into the cytoplasm
what do we get at the end of mitosis?
two identical daughter cells that also have the same DNA as their parent’s
which organisms use mitosis?
Mitosis occurs in every organism except for viruses
bacteria
some protists like amoeba
cells that are involved in the production of gametes
(as it would be covered by meiosis that leaves us with four daughter cells with half of their parent’s genetic material so that when they add up they create a cell with the correct number of chromosomes)
What happens during telophase?
During telophase the spindle fibres are broken down, a nuclear membrane is formed around each set of chromosomes to separate them from the cytoplasm and recreate the nucleus (since the nucleolus also reappears). The chromosomes are then uncoiled and subsequently return to being invisible under the microscope
What happens during cytokinesis
A ring of protein filaments is created around the equator beneath the plasma membrane. Soon the ring starts constricting , the membrane folds inwards (creating what is called cleavage) until the parent cell is divides into two daughter cells with a nucleus each.
What does cytokinesis look like in plant cells ?
In plant cells a new cell wall is created with the name of CELL PLATE in the equator that divides the cytoplasm, creating two daughter cells as a result.
