Cell Division Flashcards
What are the reasons cell dvide
Cell divide for:
Reproduction
Growth of an organism
Replacement of lost cells
What are the 3 broad categories with respect to the cell cycle
Cells that do not cycle(have permanent arrest stage). e.g. muscle cells, neurons, RBCs - once differentiated.
Cells that are induced. e.g liver cells, some immune system
Cells that divide regularly. e.g stem cells
Chromosome
Threadlike structure made of protein and DNA that carry genetic information
Euchromatin
Loosely condensed chromatin chromatin, gene rich, and active for transcription
Heterochromatin
Highly condensed chromatin structure, gene-poor, and inactive for transcription
Interphase
where a cell spend most of its life
Mitosis
shorter part of a cell life
Sister Chromatids
Sister chromatids(even when duplicated) is one chromosome
Centromere
Point where sister chromatids connect.
S-Phase (synthesis of new DNA)
The centrosome duplicates. The DNA is completely duplicated
G2 phase
The cell grows even more, it prepares for mitosis and makes proteins and organelles. At the end of the G2 phase is now when we are ready for mitosis. The cytoskeleton dismantles
What are the two major stages of a cell cycle(eukaryotic cells)
Interphase(duplicating) and mitosis
G1 phase
The duplication starts. cell grows physically larger. This is the longest stage in the cell cycle. Protein synthesis occurs
What are the different steps in interphase
G1, S(Synthesis) and G2
Cohesins
These are proteins that hold sister chromatids together.
What are the two parts in a M (mitotic) phase
Mitosis and Cytokinesis(division of the cell)
G0 Phase
Cells enter the G0 phase when they are not ready to divide. Some cells stay in this stage permanently.
Cyclin Dependent Kinases (CDK)
Multifunctional enzyme that help modify target proteins. It requires cyclins to become active.
Cyclin begins to accumulate in G1.
Maturation Promotion Factor
Universal inducer of M phase. It promotes the entrance into mitosis from G2 phase.
They add phosphate to other proteins that results in the breakdown of nuclear envelope, promotion of chromosome condensation and M- phase events
Checkpoints
These are signaling pathways of cells
What is the importance of cell cycle control?
This helps prevent accumulation of mutations in the genome.
Prevent uncontrolled division of cells.
What are the three main checkpoint in a cell cycle
G1(between G1 and S)
G2(between G2 and M)
M(between M and G1)
Neurons and non dividing cells are permanently in G0. True/ False
True
G1 Checkpoint requirements
Is the DNA damaged
Is the cell large enough and are nutrients and energy sufficient
If no, then the cell goes into G0 phase
G2 Checkpoint Requirements
Successful DNA replication
Undamaged DNA
G2 of interphase
Centrosomes (already duplicated)
The chromosomes are not condensed
Nuclear envelope and nucleolus present
Prophase
Centrosomes begin to move to the other side of the cell
Mitotic spindles form from centrosomes
Chromosomes are condensed
There is still the nuclear envelope, but no nucleus
Prometaphase
Centrosomes are at opposite ends of the cell (poles)
nuclear envelope breaks
Mitotic spindle attaches to the ‘kinetochore(centromere +protein)’
Metaphase
Sister chromatids align at the metaphase phase(middle line)
M checkpoint occurs
M checkpoint
Makes sure that the sister chromatids are aligned at the metaphase plate(middle line)
make sure sure each mitotic spindle is attached to one sister chromatid
ensures equal distribution of chromosomes into the daughter nuclei (correct separation)
What happens if M checkpoint didn’t occur
**Aneuploidy(incorrect # of chromosomes) could happen if the M checkpoint didn’t occur
Anaphase
Daughter chromosomes are dragged to the end of the poles
Telophase
Separated chromosomes start un-condensing
Nuclear envelope and Nucleus starts to form
Cytokinesis
The division of the rest of the cell into two daughter cells
Prokaryotes divide through binary fission. True/False
True
Binary fission
Asexual reproduction by the separation of body to two new bodies
