Lecture 15 Flashcards
how are 2 genetically identical daughter cells produces in each cycle
division of hypothetical eukaryotic cell with 2 chromosomes
each of daughter cells will often divided again by going through additional cell cycles
describe cell cycle
1 - chromosome replication and cell growth
2 - chromosome segregation, condensed packed dna
3 - cell division
name the 2 phases of the cell cycle
m phase
interphase
what is m phase
easily visible processes of nuclear division = mitosis and cell division = cytokinesis
what is interphase
much longer part of cycle
24 hrs - nothing happening, invisible
what is s phase
part of interphase where dna is replicated
where does dna rep happen
interphase
describe mitosis - stages generally
five stages of mitosis are shown: an abrupt change in the biochemical state of the cell occurs at the transition from metaphase to anaphase. A cell can pause in metaphase before this transition point, but once the point has been passed, the cell carries on to the end of mitosis and through cytokinesis into interphase
describe mitosis
prophase = now dna condensed
prometaphase
metaphase - cells in middle
metaphase to anaphase transition = makes sure everything is ok
anaphase - no going back now
telophase - pulled apart since glue destroyed
describe g1
rest and make sure things ok
control or gap phase that senses everything is ok
specialized phase of g1 = if stay too long exit cycle and go to gzero then differentiate
describe g1 to s phase
no going back
describe g2
cels rest and make sure everything is ok - enough nutrients
Describe phases of cell cycle
The cell grows continuously in interphase, which consists of three phases: DNA replication is confined to S phase; G1 is the gap between M phase and S phase, while G2 is the gap between S phase and M phase. In M phase, the nucleus and then the cytoplasm divide.
describe fission yeast
The fission yeast has a typical eucaryotic cell cycle with G1, S, G2, and M phases. In contrast with what happens in higher eucaryotic cells, however, the nuclear envelope of the yeast cell does not break down during M phase. The microtubules of the mitotic spindle (light green) form inside the nucleus and are attached to spindle pole bodies (dark green) at its periphery. The cell divides by forming a partition (known as the cell plate) and splitting in two. The condensed mitotic chromosomes (red) are readily visible in fission yeast, but are less easily seen in budding yeasts.
looks more similar to mammalian cells
describe budding yeast
The budding yeast has normal G1 and S phases but does not have a normal G2 phase. Instead, a microtubule- based spindle begins to form inside the nucleus early in the cycle, during S phase. In contrast with a fission yeast cell, the cell divides by budding.
small genome = fast replication, haploid genotype = easier to study yeast
describe permissive low temp
At the permissive (low) temperature, the cells divide normally and are found in all
phases of the cycle (the phase of the cell is indicated by its color).
describe at restrictive high temp
(B) On warming to the restrictive (high) temperature, at which the mutant gene product functions abnormally, the mutant cells continue to progress through the cycle until they come to the specific step that they are unable to complete (initiation of S phase, in this example). Because the cdc mutants still continue to grow, they become abnormally large. By contrast, non-cdc mutants, if deficient in a process that is necessary throughout the cycle for biosynthesis and growth (such as ATP production), halt haphazardly at any stage of the cycle—depending on when their biochemical reserves run out (not shown)
describe low vs high temp
if mutate yeast = at room temp normal
if make too hot = some mutants will arrest since mutant important for cell cycle to propgress
cdc = cell division cells
at high temp =prevents from going to s phase = proteins aggregate
describe low vs high temp when dividing
Mutated yeast at normal temp
at high temp = all stuck before cytokinesis, cells stuck and cannot divide, gone through mitosis but cannot go through cytokinesis
can rescue by adding functional gene
describe low vs high temp when dividing AvsB
(A) In a normal population of proliferating yeast cells, buds vary in size according to the cell-cycle stage.
(B) In a cdc15 mutant grown at the restrictive temperature, cells complete anaphase but cannot complete the exit from mitosis and cytokinesis. As a result, they arrest uniformly with the large buds, which are characteristic of late M phase
describe mature xenopus egg ready for fertilization
The pale spot near the top shows the site of the nucleus, which has displaced the brown pigment in the surface layer of the egg cytoplasm. Although this cannot be seen in the picture, the nuclear envelope has broken down during the process of egg maturation.
derived from frog egg, oocyte quite big, frog works diff
describe frog egg
genome from mother stays same = repairs
things divide
do not separate
every 3 min = replication no g1 or g2
predators will eat so goes fast
goes from tiny to v large cell
divides fast
describe frog egg - formal
The oocyte grows without dividing for many months in the ovary of the mother frog and finally matures into an egg. Upon fertilization, the egg cleaves very rapidly—initially at a rate of one division cycle every 30 minutes—forming a multicellular tadpole within a day or two. The cells get progressively smaller with each division, and the embryo remains the same size. Growth starts only when the tadpole begins feeding.
describe studying cell cycle in cell free system- gen
energy source = atp, study in test tube
collect cytoplasm from activated frog egg and nuclei from frog sperm and mix in test tube = cell cycle in test tube - can manipulate it
describe studying cell cycle in cell free system- formal
A large batch of activated frog eggs is broken open by gentle centrifugation, which also separates the cytoplasm from other cell components. The undiluted cytoplasm is collected, and sperm nuclei are added to it, together with ATP. The sperm nuclei decondense and then go through repeated cycles of DNA replication and mitosis, indicating that the cell-cycle control system is operating in this cell-free cytoplasmic extract.
describe mammalian cells proliferating
cells in scanning electron micrograph = rat fibroblasts
diff than yeast which have round cells
mammalian = spindle shaped and long, lumps of cells = in mitosis
describe tissue exposed to 3h thymidine - pic
going through s phase
triniated thymidine allows it be visualize
describe tissue with immunofluorescence micrograph - pic
use labelled nts
can see how many cells in s phase
antibody staining brdu
describe tissue exposed to 3h thymidine
(A) The tissue has been exposed for a short period to 3H-thymidine and the labeled cells have been visualized by autoradiography. Silver grains (black dots) in the photographic emulsion over a nucleus indicate that the cell incorporated 3H-thymidine into its DNA and thus was in S phase some time during the labeling period. In this specimen, showing the sensory epithelium from the inner ear of a chicken, the presence of an S-phase cell is evidence of cell proliferation occurring in response to damage.
describe tissue with immunofluorescence micrograph
(B) An immunofluorescence micrograph of BrdU-labeled glial precursor cells in culture. The cells were exposed to BrdU for 4 h and were then fixed and labeled with fluorescent anti-BrdU antibodies (red). All the cells are stained with a blue fluorescent dye
describe cytometer graph
This graph shows typical results obtained for a
proliferating cell population when the DNA
content of its individual cells is determined in a
flow cytometer
what is a flow cytometer
A flow cytometer, also called a
fluorescence-activated cell sorter, or FACS, can
also be used to sort cells according to their
fluorescence
describe how cells stained in flow cytometer
The cells
analyzed here were stained with a dye that
becomes fluorescent when it binds to DNA, so
that the amount of fluorescence is directly
proportional to the amount of DNA in each cell.
what are the categories that flow cytometer shows - 3
The cells fall into three categories: those that
have an unreplicated complement of DNA and
are therefore in G1 phase, those that have a
fully replicated complement of DNA (twice the
G1 DNA content) and are in G2 or M phase, and
those that have an intermediate amount of DNA
and are in S phase.
describe distrubtion of cells - results of flow cytometer
The distribution of cells in
the case illustrated indicates that there are
greater numbers of cells in G1 phase than in G2
+ M phase, showing that G1 is longer than G2 +
M in this population.
describe cells and their phases and numbers = in flow cytometer
less than 1 - undergoing apoptosis = degraded, peak of dying cells
1 = cells in g1 phase
(if take away nutrients = cells gather in g1 and waits for more nutrients)
1-2 = cells in s phase, replication
2 - cells in g2 and m phase
3-4 = cancer if more than 2, many chromosomes
