Unit 4 - Cell Cycle Episode 1 Flashcards
Genetic Information must be copied
Copies of genetic information must be separated
Cell must divide
Cell Reproduction
Single, circularly arranged chromosomes are replicated
Identical copies are attached to the plasma membrane
Prokaryotes
Grows and gradually separation into two chromosomes
A new cell wall forms between two chromosomes
Prokaryotes
PROKARYOTES - Cell Results
Two cells with an identical copy of a chromosome
Each bacterium can divide every ___________; a single bacteria may produce millions or billions of descendants in a matter of ___________.
20 minutes; 10-20 hours
- DNA replication
- Copy separation
- Cytoplasm division
More complex in ______
Eukaryotes
EUKARYOTES - Results
Two genetically identical daughter
Autosomes no. of pairs
22 pairs
Sex chromosomes no. of pairs
1 pair
two sets of genetic information
not all eukaryotic cells are ____
Diploid
one set of genetic information
sperm cells, egg cells, spores
Haploid
THREE ESSENTIAL ELEMENTS OF
FUNCTIONAL CHROMOSOME
Centromere
Pair of Telomeres
Origin of Replication
attachment point of spindle microtubules
(filaments responsible for moving chromosomes during cell division)
constricted region that stains less strongly than the rest of the chromosome
Centromere
natural tips or ends of the linear chromosomes
stabilizes the chromosome ends
Pair of Telomeres
it is where the DNA synthesis begins
Origin of Replication
sequence of activities as a cell prepares for
division and then divides
Cell Cycle
Cell Cycle - Two Major Stages
Interphase
M phase / Mitotic
Non dividing Stage
Interphase
Dividing Stage
M phase / Mitotic
cell duplicates its chromosomes, then apportions one set into each of two resulting daughter cells
somatic cells
MITOSIS
half the amount of genetic material in
somatic cells
germ sex cells
MEIOSIS
prokaryotic cells | Binary Fission
Reproduction
normal wear and tear accidents
Renewal Or Repair
gives rise to two somatic cells from one
Mitosis
form of cell death
Greek for “leaves falling from a tree”, is a precise, genetically programmed sequence of events that is normal part of development
APOPTOSIS
Greek of Apoptosis
“Leaves Falling From Tree”
is just part of the cell cycle
includes both mitosis and cytokinesis, is usually the shortest of the cell
MITOSIS
the mitotic phase alternates with a much longer stage called interphase, which often accounts for about ____ of the cycle
90%
can be divided into subphases:
the G1 (first Gap), the S phase (Synthesis), and the G2 (second Gap)
Interphase
The G phases were misnamed as _____ when they were first observed because the cells appeared _______, but we now know that intense metabolic activity and growth occur
throughout interphase
gaps; inactive
it is the extended period of growth and development between cell divisions
Interphase
although little activity can be observed with a light, the cell is quite busy: DNA is being synthesized, RNA and proteins are being produced, and hundreds of biochemical reactions necessary for cellular functions are taking place
Interphase
in addition to growth and development, _________ includes several different checkpoints which regulate the cell cycle by
allowing or prohibiting the cell’s division
Interphase
these checkpoints, like the checkpoints in ______, ensure that all cellular components are present and in good working order before cell proceeds to the next stage
M phase
__________ are necessary to prevent cells with damaged or missing chromosomes from
proliferating
checkpoints
defects in __________ can lead to unregulated cell growth, as seen in some caners
checkpoints
by convention, interphase is divided into
three subphases:
G1, S, G2
interphase begins with ____
in ____, the cell grows, and proteins (including
lipids and carbohydrates) necessary for cell
division are synthesized; this phase typically
lasts several hours
Gap 1
a critical point termed the _____________holds the cell G1 until the cell has all the enzymes necessary for the replication of DNA
G1/S Checkpoint
before reaching the G1/S checkpoint, cells
may exit from the active cell cycle in response
to regulatory signals and pass into a nondividing phase called _________, which is a stable state during which cells usually maintain constant size
G0 Phase
after G1, the cell enters the _________ (for DNA
synthesis), in which each chromosomes
duplicate
S Phase
________must take place before the cell can
proceed to mitosis
DNA Synthesis
the cell will not be able to undergo
mitosis if DNA Synthesis is blocked by
drugs or by mutation
before the S phase, each chromosome is
____________; after the S phase, each
chromosome is composed of ____________
unreplicated; two chromatids
During _________, the cell replicates its entire
genome
S Phase
as a result, each chromosome then consists
of two copies joined at an area called the
____________
centromere
in most human cells, S phase take place ______________
8 - 10 hours
many proteins are also synthesized during
this phase, including those that form the ___________ that will pull the chromosome apart
mitotic spindle
after the S phase, the cell enters _________
in this phase, several additional biochemical
events necessary for cell division takes place
Gap 2
more proteins are synthesized during this
phase
Gap 2
membranes are assembled from molecules
made during G1 and are stored a ________________
small, empty vesicles beneath the plasma membrane
these ________ will merge with plasma
membrane to enclose the two daughter cells
vesicles
the important _____________ is reached
near the end of G2
G2/M
___________ can inhibit the activation of
some proteins that are necessary for mitosis to take place
damaged DNA
after the G2/M checkpoint has been passed,
the cell is ready to divide and enters the _________
M phase
although the length of interphase varies from
cell type to cell type, a typical dividing
mammalian cell spends about ______ in g1, ________ in S, and ______ in G2
10 hours; 9 hours; 4 hours
as ________ begins, the replicated
chromosomes are condensed enough o be
visible, when stained, under a microscope
Mitosis
the two long stands of identical chromosomal
material in a replicated chromosome are called
chromatids
at a certain point during ______, a replicated
chromosome’s centromere splits, allowing its
chromatid pair to separate into two individual chromosomes (although the centromere of a replicated chromosome appears as a constriction, its DNA is replicated)
mitosis
Mitosis occurs in both ______ and _____ cells
haploid; diploid
Mitosis is conventionally broken down into five stages: (PPMAT)
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
Overlapping with the latter stages of mitosis,
___________ completes the mitotic phase
cytokinesis
in the G2 stage of the cell cycle, just prior to
the start of M, each chromosome consists of
two sister chromatids, and the centrioles have duplicated to produce two pairs
Prophase
In prophase, the ________ condenses, so
they gradually appear shorter and fatter under the microscope
Chromatin
by late prophase, each chromosome which
was duplicated during the preceding S phase of interphase, can be seen to consists of ____________
two sister chromatids
while condensation is occurring, the
__________ shrinks and eventually disappears in most species
nucleolus
many mitotic events depend on the ____________, a structure consisting of fibers composed of microtubules made of special proteins called __________
mitotic spindle (spindle apparatus); tubulins
the ____________assembles outside the
nucleus during prophase
mitotic spindle
in most animal cells, the centrioles are ______________; higher plant cells
usually ___________ but they do have a
mitotic spindle
focal points for spindle assembly; lack centrioles
then, during mitosis, each new centriole pair
becomes the focus of a radial array of
microtubules called the _______
aster
the nuclear envelope breaks down at the end
of prophase, denoting the beginning of ______
the developing spindle now enters the former nuclear area
Prometaphase
a specialized multiprotein complex called a
__________ binds to each centromere
kinetochore
the kinetochores are the sites for the
attachment of the chromosomes to the spindle microtubules known as ____________
kinetochore microtubules
spindle microtubules that do not bind to kinetochores
also originate from each spindle pole and
overlap in the middle of the spindle
Nonkinetochore microtubules
the kinetochore microtubules orient the chromosomes so that their centromeres become aligned at the _____________, a plane halfway between the two spindles poles, with long axes of the chromosomes oriented at 90 degrees to the spindle axis
metaphase plate
the centrosomes, now at opposite ends of
the cell with microtubules radiating outward and meeting in the middle of the cell, center at the spindle poles
Metaphase
a ______________________ ensures that
each chromosome is aligned on the metaphase plate and attached to spindle fibers from the opposite poles
spindle-assembly checkpoint
it had been accepted for many years that
metaphase chromosomes are the _____________ form of chromosomes in mitosis
(and meiosis)
most condensed
recently, examination of __________________________________ taken with high power microscopes has revealed that further chromosomes condensation occurs just after the chromosome have finished separating in the subsequent anaphase stage. This late condensation serves to minimize the potential problem of chromosome arms extending over the plane of division, which could result in mechanical
damage to the chromosomes
3D reconstructions of microscope images of living mammalian cells
Anaphase begins suddenly when the _______ holding together the sister chromatids of each chromosome are cleaved by an enzyme called ______
cohesins; separase
once separated, the chromatids become ______________ that move toward
opposite ends of the cell
full fledged chromosomes
during anaphase, the joined centromeres of
sister chromatids separate, giving rise to ______________
two daughter chromosomes
once the paired kinetochores on each
chromosome separate, the sister chromatid
pairs undergo ____________ and the daughter chromosomes move toward the
opposite poles
disjunction (separation)
the daughter chromosomes are pulled toward the opposite poles of the cell by the shortening microtubules attached to the kinetochore
Anaphase
the microtubules that connect the chromosomes to the spindle poles are
composed of subunits of a protein called _____
tubulin
chromosome movement is due to the disassembly of _____________ at both the kinetochore end (called the end) and the spindle end (called the end) of the spindle fiber
tubulin
special proteins called ___________________ disassemble tubulin molecules from the spindle and generate forces that pull the chromosome toward the spindle pole
molecular motors
at the start of _________, the two sets of daughter chromosomes are assembled into two groups of opposite ends of the cell
telophase
the chromosomes begin to uncoil and assume the elongated sate characteristic of interphase
telophase
a nuclear envelope forms around each group of chromosomes, the spindle microtubules disappear, and the nucleolus or nucleoli reform
Telophase
at this point, nuclear division is complete, and the new cell now has two nuclei
Telophase
is the division of cytoplasm usually, it follows the nuclear division stage of mitosis and is
completed by the end of telophase
Cytokinesis
compartmentalizes the two new nuclei into separate daughter cells, completing mitosis and cell.
Cytokinesis
In animal cells, __________ occurs by a process known as cleavage
cytokinesis
the first sign of cleavage is the appearance of a _____________, a shallow groove in the cell surface near the old metaphase plate
cleavage furrow
on the cytoplasmic side of the furrow is a contractile ring of actin microfilaments associated with molecules of the protein ______
myosin
the actin microfilaments interact with the
myosin molecules, causing the ring to _______
contract
Stable, nondividing period of variable length
G0 phase
Growth and development of the cell; G1/S checkpoint
G1 phase
Synthesis of DNA
S phase
Preparation for division; G2/M checkpoint
G2 phase
Chromosomes condense and mitotic spindle forms
Prophase
Nuclear envelope disintegrates, and spindle microtubules anchor to kinetochores
Prometaphase
Chromosomes align on the metaphase plate: spindle-assembly checkpoint
Metaphase
Sister chromatids separate, becoming individual chromosomes that migrate toward spindle poles
Anaphase
Chromosomes arrive at spindle poles, the nuclear envelope re-forms, and the condensed chromosomes relax
Telophase
Cytoplasm divides; cell wall forms in plant cells
Cytokinesis
from a single cell, the cell cycle produces two
cells that contain the same genetic instructions
the resulting daughter cells are genetically
identical with each other and with their parent
cell because DNA synthesis in the S phase
creates an exact copy of each DNA molecule,
giving rise to two genetically identical sister
chromatids
mitosis then ensures that one of the two
sister chromatids form each replicated
chromosome passes into each new cell
Genetic Consequences of the Cell Cycle
