cell cycle Flashcards
protein complex which initiates the mitotic phase of the cell cycle
Mitosis Promoting Factor (Cyclin B, CDC2)
one that oscillates in quantity during the cell cycle
Cyclin B
- one whose quantity is constant
- a kinase (an enzyme that transfers a phosphate group on to a protein by
phosphorylation)
CDC2
CDC2 kinase is only functional when it is combined with cyclin which is referred as
__________________________
cyclin-dependent kinase (CDK)
Once mitosis has been initiated, ____________________ or
_________________:
1. degrades the Cyclin B protein of MPF
2. permits the separation of the sister chromatids at the start of anaphase
anaphase-promoting complex (APC), cyclosome
refers some points in the cell cycle which allow the cell to make sure that various events
have been properly completed before the next phase begins
Checkpoints
If the _______________________ detects damage, the __________ protein targets the cell for regulated
death (apoptosis)
G1/S Checkpoint, p53
_________________________
a. ensures that spindle fibers are attached to every kinetochore before the sister
chromatids attempt to separate
b. involves several proteins including ___________________________________
(binds to kinetochore)
Spindle Attachment Checkpoint, mitotic arrest-deficient protein 2 (MAD2)
_________________ only occurs among somatic cells or body cells.
It is a form of eukaryotic cell division that produces
two daughter cells with the same genetic component
as the parent cell.
Mitosis
___________________________________
a. -Chromatin in the nucleus begins to condense and becomes visible in the light
microscope as chromosomes
b. The nucleolus
disappears
c. Centrioles begin moving
to opposite ends of the cell
and fibers extend from the
centromeres; some fibers
cross the cell to form the
mitotic spindle
d. The number of
microtubules that attach to
each kinetochore differs in
different species; 1
microtubule attaches per
kinetochore in yeast 4-
7/kinetochore in cells of rat
fetus 70 to 150 attach in the
plant Haemanthus katherinae
PROPHASE
_________________________
a. The nuclear membrane dissolves, marking the beginning of prometaphase
b. Proteins attach to the centromeres creating the kinetochores
c. Microtubules attach at the kinetochores and the chromosomes begin moving
PROMETAPHASE
____________________________
Spindle fibers align the chromosomes along the middle of the cell nucleus; line is
referred to as the ______________________; this organization helps to ensure that in the next
phase, when the chromosomes are separated each new nucleus will receive one copy
of each chromosome
METAPHASE, metaphase plate
________________________________________
a. The paired chromosomes separate at the kinetochores and move to opposite side of
the cell. Motion results from a combination of kinetochore movement along the spindle
microtubules and through the physical interaction of polar microtubules
ANAPHASE
____________________________________
a. Chromatids arrive at opposite poles of cell, and new membranes form around the
daughter nuclei
b. The chromosomes disperse and are no longer visible under the light microscope
c. The spindle fibers disperse, and cytokinesis or the partitioning of the cell may also
begin during this stage
TELOPHASE
In animal cells, ___________________ results when a fiber ring composed of protein called actin around the center of
the cell contracts pinching the cell into two daughter cells, each with one nucleus.
cytokinesis
separation of the genetic material in a mitotic nuclear division
karyokinesis
separation of the cell cytoplasm in a cellular division
cytokinesis
is important for the maintenance of the chromosomal set; each cell formed receives chromosomes
that are alike in composition and equal in number to the chromosomes of the parent cell.
Mitosis
The main goal of _________________________________ is to preserve the chromosomes of the parent cells to the daughter cells in order
to attain genetic continuity.
MEIOSIS
Sex cells (gametes), which are haploid cells, undergo a special type of cell division which is properly
called “___________________”.
meiosis
Two successive nuclear divisions occur in Meiosis, _________________________and ___________________________
Meiosis I (Reduction), Meiosis II (Division)
Meiosis produces
_______________________ cells. Mitosis produces ____________________ cells
4 haploid, 2 diploid
The old name for meiosis was ________________________
reduction/division.
is the process of linking of the replicated homologous chromosomes. The
resulting chromosome is termed tetrad, being composed of two chromatids from each
chromosome, forming a thick (4-strand) structure
Synapsis
- may occur at this point; during crossing-over chromatids break and may be
reattached to a different homologous chromosomes; crossing over between homologous
chromosomes produce chromosomes with new association of genes and alleles
Crossing Over
means thin thread; chromosomes first become visible as long, threadlike structures; initial phase of condensation of the chromosomes
Leptotene
means paired thread; marked by lateral pairing, or synapsis, of
homologous chromosomes, beginning at the chromosome tips
Zygotene
- means thick thread; condensation of the chromosome continues;
throughout this period, the chromosomes continue to shorten and thicken;
genetic exchange or crossing over happens here; but crossing over is not
apparent until the transition to diplotene
Pachytene
means double thread; the synapsed chromosomes begin to separate,
and the diplotene chromosomes begin to double; each cross connection called
chiasma, is formed by a breakage and rejoining between nonsister chromatids
Diplotene
final period; means moving apart; the homologous chromosomes
seem to repel each other and the segments not connected by chiasmata move
apart; near the end of Diakenesis, the formation of a spindle is initiated and the
nuclear envelope breaks down.
Diakenesis
A Tetrads line-up along the equator of the spindle
b. Spindle fibers attach to the centromere region of each homologous chromosome pair;
other metaphase events as in mitosis
METAPHASE I
when tetrads separate, and are drawn to opposite poles by the spindle fibers. The
centromeres in _________ remain intact
ANAPHASE I
a. Similar to telophase of mitosis, except that only one set of (replicated) chromosomes is in
each “cell”
b. Depending on species, new nuclear envelopes may or may not form; some animal cells
may have division of the centrioles during this phase
TELOPHASE I
A spindle apparatus forms
Prophase II
Chromosomes are positioned in the metaphase plate as in mitosis
b. Because of crossing over in meiosis I, the two sister chromatids of each chromosomes
are “not” genetically identical
c. The kinetochores of sister chromatids are attached to microtubules extending from
opposite poles
Metaphase II
a. The centromeres of each chromosome finally separate, and the sister chromatids come
apart
b. The sister chromatids of each chromosome now move as two individual chromosome
Anaphase II
Nuclei form, the chromosome begin decondensing, and cytokinesis occurs
b. Meiotic division of one parent cell produces four daughter cells, each with a haploid set
of (unreplicated) chromosome
c. Each of the four daughter cells is genetically distinct from the other daughter cells and
from the parent cell
Telophase and Cytokinesis
