Cell Division Prt 1 Flashcards
One purpose of cell division is_______. In this process, a preexisting cell divides to p roduce two new cells.
asexual reproduction
Original cell
2 new cells
Mother cell
Daughter cells
is how bacterial cells p roliferate. In addition, certain unicellular eukaryotes, such as the amoeba and baker’s yeast ( Saccharom y ces cerevisiae ) , can reproduce _______
Asexual reproduction
Another purpose of cell division is __________ Species such as p lants, animals, most fungi, and some p rotists are derived from a sin g le cell that has under g one repeated cell divisions.
multicellularity
process of cell division requires the
duplication
organization
distribution of the chromosomes.
Prior to cell division, bacteria duplicate their circular chromosome ; the y then distribute- a copy into each of the two dau g hter cells. This process, known as_______
binary fission
the circular chromosomes of bacteria are in direct contact with the ______
Cytoplasm
Prior to cell division, bacterial cells __________ their chromosomal DNA. This p roduces two identical co p ies of the g enetic material
Copy or replicate
A p rotein called_____ assembles into a rin g at the future site of the septum. ____ is thou g ht to be the first protein to move to this division site.
FtsZ
FtsZ recruits other p roteins that produce a ______, which is a new cell wall between the dau g hter cells
Septum
FtsZ is evolutionaril y related to a eukaryotic p rotein called_____.
It is the main component of microtubules, which p la y a key role in chromosome sortin g in eukaryotes.
tubulin
As a result of binar y fission, a bacterial cell called the_________ has divided into two dau g hter cells. Each dau g hter cell receives a co py of the chromosomal g enetic material. Except when rare mutations occur, the dau g hter cells are usuall y g eneticall y identical because the y contain exact co p ies of the g enetic material from the mother cell.
mother cell
The common outcome of eukar y otic cell division is to produce _______ that have the same number and t yp es of chromosomes as the ori g inal mother cell.
two daughter cells
Eukar y otic cells that are destined to divide advance throu g h a series of p hases known as the
Cell cycle
Cell cycle
G1, S phase, G2, M
Phases are collectively known as interphase
G 1, S, and G 2
May remain permanently , or for lon g p eriods of time, in a p hase of the cell cycle called ____. A cell in the ___ G0 phase is either temporarily not advancin g throu g h the cell cycle or, in the case of terminall y differentiated cells, such as most nerve cells in an adult mammal, will never divide a g ain.
G0
is a nondividing stage
G0 phase
Durin g the ___ phase, a cell ma y p re p are to divide.
G1
____ phase ma y accumulate molecular changes and reach a restriction p oint and thereby be committed on a pathway that leads to cell division
G1
After a cell has reached a______, it will advance through the remainder of G1, and then proceed through the S, G2, and M phases to complete the cell cycle.
restriction point
Once past the restriction point, the cell then advances to the_____ during which the chromosomes are replicated.
S phase
After replication, the two copies are called______.
They are joined to each other at a region of DNA called the_____ to form a unit known as a pair of sister chromatids, or a____
chromatids
centromere
dyad
A single chromatid within a dyad is called a_____.
An unreplicated chromosome can also be called a____.
monad
When____ phase is completed, a cell has twice as many chromatids as it had
chromosomes in the ____phase.
S
G1
The______ is a group of proteins that are bound to the centromere. These proteins help to hold the sister chromatids together and also play a role in chromosome sorting, as discussed later.
kinetochore
During the _____, the cell accumulates the materials that are necessary for nuclear and cell division.
G2 phase
Finally, the cell advances into the M phase of the cell cycle, when _____ occurs.
Mitosis
The primary purpose of _____ is to distribute the replicated chromosomes, dividing one cell nucleus into two nuclei, so that each daughter cell receives the same complement of chromosomes.
Mitosis
human cell in the ____ phase has 92 chromatids, which are found in 46 pairs.
During mitosis, these pairs of chromatids are separated and sorted to produce two nuclei that contain 46 chromosomes each.
G2
Two daughter cells are formed by a process called______.
cytokinesis
Bacteria divide by
binary fission
To divide, eukaryotic cells advance through a
cell cycle
Prior to cell division, eukaryotic chromosomes are replicated to form
sister chromatids
is involved in the organization and sorting of chromosomes
mitotic spindle
indle a pp aratus is formed from_____ , which are structures found in eukar y otic cells from which microtubules g row.
microtubule-organizing centers ( MTOCs )
are produced from the rapid polymerization of tubulin proteins.
Microtubules
In animal cells, the mitotic spindle is formed from two MTOCs called.
centrosomes
Each centrosome is located at a
spindle pole
A pair of______ at right angles to each other is found within each centrosome of animal cells.
centrioles
3 types of microtubules
Aster
Polar
Kinetochore
They are important for the positioning of the spindle apparatus within the cell and later in the process of cytokinesis.
aster microtubules
The_____ microtubules emanate outward from the centrosome toward the plasma membrane.
aster
project toward the region where the chromosomes are found during mitosis–the region between the two spindle poles.
The polar microtubules
that overlap with each other play a role in the separation of the two poles. They help to “push” the poles away from each other.
Polar microtubules
The______ microtubules have attachments to kinetochores, which are protein complexes bound to the centromeres of individual chromosomes.
kinetochore
allows cells to organize and separate chromosomes so that each daughter cell receives the same complement of chromosomes.
mitotic spindle
Prior to mitosis, the cells are in interphase, during which the chromosomes are______-less tightly compacted–and found in the nucleus
decondensed
, the chromosomes have already replicated to produce 12 chromatids that are joined as six pairs of sister chromatods
prophase
As prophase proceeds, the _____begins to dissociate into small vesicles.
At the same time, the_____ condense into more compact structures that are readily visible by light microscopy.
The_____also begins to form, and the______, which is the site of ribosome assembly, . disappears.
nuclear membrane
chromatids
mitotic spindle
nucleolus
As mitosis advances from prophase to pro-metaphase, the______ move to opposite ends of the cell and demarcate two spindle poles, one within each of the future daughter cells.
centrosomes
Once the nuclear membrane has dissociated into vesicles, the spindle fibers can interact with the sister chromatids.
This interaction occurs in a phase of mitosis called
prometaphase
By the end of prometaphase, the____ is completely formed.
mitotic spindle
MetaphaseEventually, the pairs of sister chromatids align themselves along a plane called the
metaphase plate
when this alignment is complete, the cell is in______ of mitosis.
At this point, each pair of chromatids (each dyad) is attached to both poles by________ microtu-bules.
metaphase
kinetochore
The pairs of sister chromatids have become organized into a single row along the metaphase plate. When this organizational process is finished, the chromatids can be equally distributed into two daughter cells.
Metaphase
, the connection that is responsible for holding the pairs of chromatids together is broken
anaphase
Each chromatid or monad, now an individual chromosome, is linked to only one of the two poles.
Anaphase
As anaphase proceeds. the chromosomes move toward the pole to which they are attached.
This movement is due to a shortening of the_____ microtu-bules.
kinetochore
During______, the chromosomes reach their respective poles and decondense
telophase
nuclear membrane now re-forms to produce two separate nuclei.
Telophase
this process has produced two nuclei that contain six chromosomes each. The nucleoli have also reappeared.
Telophase
In most cases, mitosis is quickly followed by______, in which the two nuclei are segregated into separate daughter cells.
cytokinesis
cytokinesis also segregates cell organelles such as ___________ into daughter cells.
mitochondria and chloroplasts
In animal cells, cytokinesis begins shortly after_____. A contractile ring, composed of myosin motor proteins and actin filaments, assembles adiacent to the plasma membrane.
______hydrolyzes ATP, which shortens the ring and thereby constricts the plasma membrane to form a cleavage furrow that ingresses, or moves inward
Ingression continues until a midbody structure is formed that physically pinches one cell into two.
anaphase
Myosin
In plants, the two daughter cells are separated by the formation of a
cell plate
The_______ is involved in sorting the chromosomes and promoting the division of one cell into two daughter cells.
mitotic spindle
The____ microtubules overlap with each other and push the poles apart during anaphase.
polar
The ____microtubules help to orient the spindle in the cell and play a role in cytokinesis.
aster
The______ microtubules attach to chromosomes and aid in their sorting.
They are needed to align the chromosomes at the metaphase plate and to pull the chromosomes to the poles during anaphase.
kinetochore
