Overview Flashcards
what is the life cycle of organisms (meiosis, fertilization, mitosis, meiosis, fertilization,…) in eukaryotes based on?
based on the life cycle of the cell
what is a cell cycle?
it is a series of biological events that are repeated
Into what is the cell cycle divided? and based on what?
divided into 2 major phases based on cellular activities that are readily visible by light microscopy
what are these phases?
the M phase or cell division (usually mitosis and cytokinesis) and the interphase
how much does interphase last in comparison to cell division in most cells?
interphase lasts longer than cell division
what is the average duration time of mitosis and interphase?
mitosis is about an hour whereas interphase lasts about 19 hours
duration time varies according to what?
according to organism, tissue and age of the cell
cell division and interphase are subdivided into how many stages?
5 and 3 stages respectively
which cell types don’t divide, therefore they are out of the cell cycle?
certain cell types that are highly differentiated such as muscle fibers, red blood cells and neurons
can such cells stay in any one of the cell cycle stages? If no, why?
can not stay in any one of the cell cycle stages since the cycle is stopped
when non dividing cells leave the cell cycle, what do they enter?
they enter a quiescent state named G0
what happens to certain cell types such as hepatocytes? (according to G0 and when do they leave it?)
enter G0 temporarily and leave it in case of liver regeneration
in others such as neurons, what is their situation according to G0?
they are permanently blocked in G0
when examining dividing cells with a microscope, what does it show? and why?
shows few cells in M phase. This is because interphase represents most of cell cycle duration while M phase is rapid
what does this rule show? give example: what happens during segmentation of fertilized eggs?
shows many exceptions, for instance during segmentation of fertilized eggs, interphase is very short and the zygote divides many times without increasing its size
why are the 2 phases intimately related?
since the events that occur during M phase would be impossible without the preparation during interphase.
That is, the biological processes that take place during interphase aim at preparing the events of M phase
interphase is divided into how many stages? name them
3 stages: G1 (gap1), S (synthesis of DNA), and G2 (gap2)
each stage is characterized by?
Each stage is characterized by specific processes
What happens to the cell during interphase? What are the daughter cells supplied with?
the cell doubles its content (organelles, proteins, lipids, carbohydrates,…) so that the daughter cells are supplied with the necessary cellular structures organelles and components
what happens to proteins, carbohydrates and lipids throughout the entire interphase period?
they are synthesized
when does DNA replication (synthesis) occur and what does it produce
occurs during S phase only and produces the sister chromatids of each chromosome
By what are these sister chromatids remain tightly joined?
by their centromeres and cohesion along their length
What happens to the DNA amount during G1, S phase and G2?
DNA amount is constant during G1, it increases during S to reach twice the amount in G1 and finally it is constant again during G2
During M phase, what happens to DNA quantity per cell and why?
DNA quantity per cell is reduced since sister chromatids are separated and distributed in 2 daughter cells
What happens to centrioles of a centrosome as the cell makes the G1-S transition? when do they separate?
they duplicate as the cell makes the G1-S transition but they don’t separate from each other until late prophase
What is centriole duplication?
centriole duplication is the assembly of a new centriole at right angles with respect to each old one
