Lecture 9- Mitosis Flashcards
State the stages of the cell cycle (with Mitosis considered 1) and how long they take relatively in human cells
Mitosis (<1 Hour) G1 ( 5-6 hours) S phase (10-12 hours) G2 ( 4-6 hours) In total about 24 hours
What is apoptosis?
Programmed cell death by cell’s own enzymes, when body finds an error in the cell or when it grows old
*Describe the events of apoptosis
- Cyclins (internal proteins find a problem in the cell
- Nucleus collapses
- Chromatin and nucleus fragments condense
- Plasma membrane blisters, and blebs form
- Blebs leave the damaged cell
- Cell fragments are phagocytized by WBC
How many main cell checkpoints are conducted in a cell cycle, where are they, and what conducts them?
3 main checkpoints by cyclins (nternal proteins enzymes) In G1, G2, and M )Late metaphase/ Early anaphase))
*Is it true that only 3 checkpoints are conducted in cell cycle?
No! There are 3 main checkpoints, but checkpoints in general are conducted throughout the cell cycle
What is the cellular genome?
The collection of DNA, in the human body, mainly the 46 chromosomes
What are somatic cells?
Non sex cells (contain diploid number of chromosomes)
What are the 5 stages of mitosis?
Prophase Prometaphase Metaphase Anaphase Telophase
What does a chromatid contain?
A DNA double helix and histone proteins ∴ 2 DNA strands with histone proteins
How many chromosomes do gamete cells have?
half that of somatic cells (23 for humans)
At which point in the human cell cycle are there 92 functional chromosomes?
At no point are there 92 functional chromosomes
What events take place at Early prophase?
- centrosome duplication (1->2)
What events occur at prophase?
- condensation of chromatin fibers, now observable with light microscope ∴ Histone proteins deassocate with chromosomes
- Nucleolous disappear
- formation of mitosis spindle and asters
- centrosome begin to move away, propelled by lengthing microtubules
What events occur at prometaphase?
- Nuclear envelope fragments
- kinetochore develops at each chromatid
- beginning of attachment of kinetiochore microtubules to kinetochores
- Non kinetochore microtubules interact with those in opposite pole( never directly touch)
What happens at Metaphase?
- Centrosome are now at the poles of the cell
- the chromosomes are now at the metaphase plate
- each kinetochore now has microtubules attached to it
- there are still non kinetochore microtubules
What is the function of non-kinetochore microtubules?
Elongate the cell and keep the cell integrity
What happens during Anaphase?
- Sister chromatids move apart at a rate of 1 μm/min (now
- Cell elongates as the non kinetochore microtubules lengthen
- by the end, two ends of the cell have the complete collection of chromosomes
What happens during Telophase?
- 2 daughter nuclei begin to form
- Nuclear envelopes arise from fragments of nuclear envelopes and portions of the endomembrane system
- chromosomes decondense
- mitotic spindles are broken down
- mitosis is now complete
What is cytokinesis and when does it start and end?
it is the division of the cytoplasm
Anaphase–> G1
Explain the differences in cytokinesis between plant and animal cells
in animal cells, a cleavage furrow is formed (indentation of membrane between 2 daughter nuclei), it is deepened by actin filaments contractile ring
in plant cells, cell walls prevent formation of cleavage burrow, instead, Golgi apparatus vesicles form the cell plate
What is the shortest phase in the cell cycle?
Anaphase
What is the longest phase?
Metaphase
