Cell Cycle Flashcards
The life of a cell from the time it is first formed during the division of a parent cell until its division into two daughter cells
- involves the distribution of DNA to daughter cells
cell cycle
If the division of a cell becomes uncontrolled, what happens?
It becomes cancer cells
(cancer - uncontrolled cell growth)
Functions of the Division of Cells
- for reproduction
- for growth and development
- Tissue renewal - to regenerate/replace old dead cells
dispersed DNA with its associated proteins (histones) found in a chromosome
Chromatin
packaged and organized structures containing DNA, condensed
Chromosome
Chromosomes can be _________ and ______________
duplicated and unduplicated (sometimes called chromatid)
What phase spends the longest time in Cell Cycle
Interphase (especially Gap 1 phase)
A phase in interphase where these events happen:
- Growth of cytoplasm and doubling of organelles
- Produce proteins, enzymes, nutrients, and energy
- Highest rate of protein synthesis
- Movement of centrioles
First Gap Phase
A phase in interphase where these events happen:
- The cell synthesizes a copy of its DNA in a very notable process called DNA replication (when an existing DNA produces another copy of itself)
S phase (Synthesis)
A phase in interphase where these events happen:
- Continued growth, further maturation, and the production of materials that are necessary for cell division to occur
- Protein synthesis but not at a rate similar to that of the G1 phase
- Preparation for the m phase
Second Gap Phase
A phase in interphase where these events happen:
- Mitosis or Meiosis
- maybe cytokinesis
M phase
the physical process of cell division, which divides the cytoplasm of a parental cell into two daughter cells. It occurs concurrently with two types of nuclear division called mitosis and meiosis, which occur in animal cells.
- marked by the formation of cleavage furrow in animal cells
- plant cell - formation of cell plates
- begins in anaphase-telophase
cytokinesis
Cells in _________ are not actively preparing to divide. The cell is in a quiescent (inactive) stage that occurs when cells exit the cell cycle. Some cells enter this phase temporarily until an external signal triggers the onset of G1. Other cells that never or rarely divide, such as mature cardiac muscle and nerve cells, remain in here permanently.
G0 Phase
a stage in the eukaryotic cell cycle at which the cell examines internal and external cues and “decides” whether or not to move forward with division.
- Ensure that the phases are done correctly for the cell to proceed
checkpoint
The molecule inside cells that contains the genetic information responsible for the development and function of an organism. These molecules allow this information to be passed from one generation to the next.
Deoxyribonucleic Acid (DNA)
Checkpoints in Cell Cycle
- G1 checkpoint, at the G1/S transition
- G2 checkpoint, at the G2/M transition
- M checkpoint, the spindle checkpoint, at the transition from metaphase to anaphase
a checkpoint that is the main decision point for a cell – that is, the primary point at which it must choose whether or not to divide.
- is the environment favorable?
- checks for size, nutrients, growth factors, DNA damage
- enters cell cycle and proceeds to s phase
- G1 checkpoint
What happens when a cell doesn’t get a go-ahead cue from the G1 Checkpoint?
it may leave the cell cycle and enter a resting state called the G0 phase. Some cells stay permanently G0, while others resume dividing if conditions improve.
if unrepairable - apoptosis
A checkpoint that checks for DNA damage and DNA replication completeness
is the environment favorable?
- enters mitosis
G2 Checkpoint
what happens if there are errors in G2 checkpoint
If the checkpoint mechanisms detect problems with the DNA, the cell cycle is halted, and the cell attempts to either complete DNA replication or repair the damaged DNA.
If the damage is irreparable, the cell may undergo apoptosis or programmed cell death. This self-destruction mechanism ensures that damaged DNA is not passed on to daughter cells and is important in preventing cancer.
in this checkpoint, the cell examines whether all the sister chromatids are correctly attached to the spindle microtubules. Because the separation of the sister chromatids during anaphase is an irreversible step, the cycle will not proceed until all the chromosomes are firmly attached to at least two spindle fibers from opposite poles of the cell.
- triggers anaphase and proceeds to cytokinesis
M checkpoint
(Cell Cycle Control System)
to ensure that they replicate all their DNA and organelles, and divide in an orderly manner, eukaryotic cells possess a complex network of ___________________
regulatory proteins
This regulation stops the cell to proceed the cell cycle
- p53
negative regulation
This regulation allows the cell to proceed if they pass the checkpoints
- cyclin and kinase
positive regulation
family of regulatory proteins that control the progression of the cell cycle. They activate cyclin-dependent kinases (CDKs), which control cell cycle processes through phosphorylation. When a _______ and CDK form a complex, the complex will bind to a target protein and modify it via phosphorylation.
- regulatory proteins whose concentrations rise and fall at specific times during the eukaryotic cell cycle
Cyclin
enzymes that catalyze the phosphorylation of a protein resulting in a change affecting that protein’s function. is present all throughout the cell cycle but is only activated by the cyclin (Cyclin-CDK Complex)
-phosphorylation - turning on
- dephosphorylation - turning off
Kinase (Cdk)
Cyclin D
G1-Cdk
-from 1st gap phase until the end of the cell cycle (because of mitogens -Most eukaryotic cells only divide in the presence of mitogens. Mitogens stimulate cell division by increasing the amount of G1 cyclins, which trigger cells to enter Start)
- Initiates the presence of the other cyclins
- pairs with Cdk 4
Cyclin E
G1/S-Cdk
- S phase
- pairs with Cdk 2
Cyclin A
S-Cdk
- G2 phase
- pairs with Cdk 2
Cyclin B
M-Cdk
- mitosis
- pairs with Cdk
Kinases in Cell Cycle
Cdk 1, 2, 4, 6
Cyclin C
before/ at the very start of interphase
Activated ______ promotes cell cycle arrest to allow DNA repair and/or apoptosis to prevent the propagation of cells with serious DNA damage through the transactivation of its target genes implicated in the induction of cell cycle arrest and/or apoptosis
p53
- a group of proteins stimulating the growth of specific tissues. plays important roles in the regulation of cell division that drives cell proliferation. Each binds to a specific cell–surface receptor.
- It induces the cells to stop a cell cycle phase or progress to the next cell cycle stages, such as cellular proliferation. In cells, some proteins bind with receptors to activate genes that start cell growth.
Growth factors
the process by which a cell replicates its chromosomes and then segregates them, producing two identical nuclei in preparation for cell division. It is generally followed by equal division of the cell’s content into two daughter cells that have identical genomes
Mitosis
What cells are involved in mitosis
somatic cells/body cells
stages of mitosis in order
Prophase, Prometaphase, Metaphase, Anaphase, Telophase, Cytokinesis
A stage in mitosis where:
- Chromosomes condense and become visible
- spindle fibers emerge from the centrosomes
- nuclear envelope breaks down
- nucleolus disappears
prophase
A stage in mitosis where:
- chromosomes continue to condense
- kinetochores appear at the centromere
- spindle fibers attach to kinetochores
- centrosomes move toward opposite poles
- involves spindle fibers, centrosomes, chromosomes, and nuclear membrane
prometaphase
A stage in mitosis where:
- mitotic spindle is fully developed, centrosomes are at opposite poles of the cell
- chromosomes are lined up at the metaphase plate
- each sister chromatid is attached to a spindle fiber originating from opposite poles
- involves spindle fibers, centrosomes, and chromosomes
metaphase
A stage in mitosis where:
- cohesin proteins binding the sister chromatids together break down
- sister chromatins (now called chromosomes) are pulled toward opposite poles
- non-kinetochore spindle fibers lengthen, strengthening the cell
anaphase
A stage in mitosis where:
- chromosomes arrive at opposite poles and begin to decondense
- nuclear membrane material surrounds each set of chromosomes
- the mitotic spindle breaks down
- involves chromosomes, centrosome, and nucleus
telophase
mitosis in a plant cell
interphase, early prophase, prophase, late prophase, transition to metaphase, metaphase, anaphase, telophase
what cell does mitosis produce
diploid cell (2n=46)
One of the strands of the replicated chromosome. It can be joined together by the Centromere.
chromatid
A paired barrel-shaped organelle containing 9 triplets of microtubules. It helps in moving the Chromosomes away from each other and to the opposite sides of the cell to make sure that each daughter cell contains the appropriate number of Chromosomes.
centrioles
A part of chromosome that holds sister chromatids together. Chromosomes are counted based on the number of Centromeres.
centromeres
a protein complex assembled on the centromeric region of DNA. It provides the major attachment point for the spindle microtubules during mitotic or meiotic division to pull the chromosomes apart.
kinetochore
It is a region of repetitive DNA sequence found at the ends of chromosomes that protects and allows the Chromosomes to replicate properly during cell division.
telomere
It consists of a pair of homologous chromosomes with four chromatids. It is formed for crossing over to happen.
tetrad
spindle fibers that pull the centrosomes apart
polar spindle fibers
spindle fibers that attach to the cell membrane
aster spindle fibers
a type of cell division in sexually reproducing organisms that reduces the number of chromosomes in gametes (the sex cells, or egg and sperm).
- produces varied cells
- greek word meaning “lessening”
meiosis
what cells are involved in meiosis
gametes/reproductive cells/sex cells/germ cells
two cell division of meiosis
meiosis I/reductional division & meiosis II (equational division)
what cell does meiosis produce
haploid cells (23 chromosomes)
a protein complex that mediates sister chromatid cohesion, homologous recombination, and DNA looping.
- holds sister chromatids together after DNA replication until anaphase when removal of cohesin leads to separation of sister chromatids.
cohesin proteins
what separates sister chromatids
active separase
exchange of chromosome segments of non-sister chromatids creating a new combination of genes in the gametes
crossing over
pairing of two chromosomes that occurs during meiosis
synapsis
meiosis
- centrosomes are visible
-nuclear membrane
disappears - “crossing over”
prophase I
meiosis
-Tetrads line up along the
metaphase plate
metaphase I
meiosis
- paired homologous
chromosomes separated and
migrated
anaphase I
meiosis
the chromosomes arrive at opposite poles of the cell. In some organisms, the nuclear membrane re-forms and the chromosomes decondense, although in others, this step is skipped—since cells will soon go through another round of division, meiosis II. Cytokinesis usually occurs at the same time as telophase I, forming two haploid daughter cells
telophase I
what division of meiosis is like mitosis?
meiosis II
a period of rest that cells of some species enter during meiosis between meiosis I and meiosis II
interkinesis
non-matured sperm
spermatids
what happens to the daughter cells released in meiosis in females
only 1 is released in the ovary (ovum), others become polar bodies and (may) undergo apoptosis
