mitosis Flashcards
eukaryotic cell cycle
– Cell grows.
– DNA is replicated.
– Mitotic cell division produces daughter cells identical to the parent.
– Repeat.
The timing of replication and cell division is highly regulated.
what is cell division
Cell Division — process by which a cell divides into 2 new cells
why do cells need to divide
Living things grow by producing more cells, NOT because each cell increases in size
Repair of damaged tissue
If cell gets too big, it cannot get enough nutrients into the cell and wastes out of the cell
what happens before cell division
Before cell division occurs , the cell replicates (copies) all of its DNA, so each daughter cell gets complete set of genetic information from parent cell
Each daughter cell is exactly like the parent cell – same kind and number of chromosomes as the original cell
how do unicellular organisms reproduce
Many organisms, especially unicellular organisms, reproduce by means of cell division – called asexual reproduction – Ex: bacteria
DNA
DNA is located in the nucleus and controls all cell activities including cell division
Long and thread-like DNA in a non-dividing cell is called chromatin
Doubled, coiled, short DNA in a dividing cell is called chromosome
Consists of 2 parts: chromatid and centromere
chromosome structure
2 identical “sister” chromatids attached at an area in the middle called a centromere
When cells divide, “sister” chromatids separate and 1 goes to each new cell
2 major phases of eukaryotic cell cycle
Interphase (3 stages)
– DNA is not condensed
Mitosis (4 stages + cytokinesis)
– Nuclear division & division of cytoplasm
– DNA condensed
cell cycle
Cell Cycle – series of events cells go through as they grow and divide
Cell grows, prepares for division, then divides to form 2 daughter cells – each of which then begins the cycle again
interphase
Interphase—period of cell growth and development
DNA replication (copying) occurs during Interphase
During Interphase the cell also grows, carries out normal cell activities, replicates all other organelles
The cell spends most of its life cycle in Interphase
three sub-stages of interphase
Gap 1 – cell grows in size
– organelles replicated
Synthesis – replication of DNA
– synthesis of proteins
associated with DNA
Gap 2 – synthesis of proteins
associated with mitosis
What is mitosis
Division of somatic cells (non-reproductive cells) in eukaryotic organisms.
A single cell divides into two identical daughter cells.
Daughter cells have same number of chromosomes as does parent cell.
why does mitosis occur
So each new daughter cell has nucleus with a complete set of chromosomes
When the cell is not dividing…
DNA molecules are in extended, uncondensed form = chromatin
Cell can only replicate and transcribe DNA when it is in the extended state.
When the cell is preparing for division…
DNA molecules condense to form chromosomes prior to division.
each chromosome is a single molecule of DNA
easier to sort and organize the replicated DNA into daughter cells
four sub-phases of mitosis
PMAT
prophase
metaphase
anaphase
telophase
prophase
chromosomes condense
nuclear envelope disappears
spindle fibers form
(spindle fibers are specialized microtubules radiating out from centrioles)
chromosomes are captured by spindle
metaphase
chromosomes align along the equator of the cell, with one chromatid facing each pole
Spindle fibers connect to chromosomes
anaphase
sister chromatids separate
spindle fibers attached to kinetochores shorten and pull chromatids towards the poles.
free spindle fibers lengthen and push the poles of the cell apart
telophase
spindle fibers disintegrate
nuclear envelopes form around both groups of chromosomes
chromosomes revert to their extended state
cytokinesis occurs, enclosing each daughter nucleus into a separate cell
cytokinesis
Cytokinesis — the division of the rest of the cell (cytoplasm and organelles) after the nucleus divides
what happens after mitosis and cytokinesis
After mitosis and cytokinesis, the cell returns to Interphase to continue to grow and perform regular cell activities
plant cell cytokinesis
Plant cells undergo cytokinesis by forming a cell plate between the two daughter nuclei.
animal cells cytokinesis
Animal cells undergo cytokinesis through the formation of a cleavage furrow. A ring of microtubules contract, pinching the cell in half.
