Cell cycle Flashcards
Nuclear division (mitosis) and cytoplasmic division (cytokinesis) are 2 phases known as ___ phase and can be seen in a microscope
M
Interphase can be divided into phases. The only phase that can be seen microscopically is ___ phase. The other main phases are called ___ (because under a microscope not much is happening)
S
Gaps
What are the three distinct periods in interphase?
Gap period (G1) Synthetic period (S) Gap period (G2)
What happens in G1 at interphase?
The cell grows and carries out normal metabolic and biochemical functions
What happens in S at interphase?
DNA synthesis (replication)
What happens in G2 at interphase?
centrioles (spindle pole bodies) duplicate
When does a cell go into G0 (quiescence)?
If something goes wrong a cell goes into G0. It dies if the conditions don’t improve. However, if conditions improve, it goes into G1.
The length of the cell cycle is ____ variable
very
Where does most of the variability in the cell cycle take place?
during G1. Other phases are fairly constant in length
When does the critical checkpoint (START) take place?
At the end of G1
What happens if growth/environment is unfavourable?
Cells do not pass START
How is the cell cycle regulated?
Cytoplasmic control factors Cell division and cell size External growth factors Senescence (ageing) Loss of control
What happens to cells if cell cycle time was constant and nutrition is insufficient?
Cells would be too small on entering division so cells get smaller and smaller
What happens to cells when food becomes scarce (with nutritional control?
Cell size is maintained. The cell cycle lengthens
Cells which respond to growth factors have special _________ on their membranes
(TK) receptors
The ability to change the normal growth rate is important in ________ healing
wound
Growth factors trigger activation of ___ proteins which in turn accelerate the rate of cell growth and division
ras
The probability of entering G0 depends on the number of times the cell has already ________
divided
As you get older, the number of cell cycles _______
decreases
The process of senescence is linked with _________ shortening
telomere
Raising levels of telomere in patients may slow down _______, but also increases the risk of developing cancer
ageing
What are the four strategies in which the number of cells in an adult tissue can be kept constant?
No renewal i.e. tissues with permanent cells
Renewal by simple duplication
Renewal by stem cells
Renewal by multipotent stem cells
If a cell has differentiated can it change its specialised character in diverse environments?
No, once it has differentiated, it maintains its specialised character
Which cells don’t undergo renewal and don’t appear to divide and cannot be replaced if they are lost or damaged?
Nerve cells
Heart muscle cells
Lens cells of the eye
Renewal by simple duplication - cells are constantly dying and being replaced. Rates of renewal vary considerably: e.g.
gut lining ___-____ days
pancreas > 1 year
3-6
Stem cells are NOT differentiated by are________
determined (pre-specified)
Stem cells divide ______ or ________
symmetrically or asymmetrically
Renewal by multipotent stem cells e.g. _______
Blood cell formation (haemopoiesis)
What does totipotent mean?
ability of a single cell to divide and produce all of the differentiated cells in an organism, including extra-embryonic tissues
What does pluripotent mean?
stem cells that have he potential to differentiate into any of the three germ layers
What does multipotent mean?
describes cells which have the potential to differentiate into multiple, but limited cell types
