Lecture 15

Question 1

how are 2 genetically identical daughter cells produces in each cycle

Answer 1

division of hypothetical eukaryotic cell with 2 chromosomes
each of daughter cells will often divided again by going through additional cell cycles

Question 2

describe cell cycle

Answer 2

1 - chromosome replication and cell growth
2 - chromosome segregation, condensed packed dna
3 - cell division

Question 3

name the 2 phases of the cell cycle

Answer 3

m phase
interphase

Question 4

what is m phase

Answer 4

easily visible processes of nuclear division = mitosis and cell division = cytokinesis

Question 5

what is interphase

Answer 5

much longer part of cycle
24 hrs - nothing happening, invisible

Question 6

what is s phase

Answer 6

part of interphase where dna is replicated

Question 7

where does dna rep happen

Answer 7

interphase

Question 8

describe mitosis - stages generally

Answer 8

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

Question 9

describe mitosis

Answer 9

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

Question 10

describe g1

Answer 10

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

Question 11

describe g1 to s phase

Answer 11

no going back

Question 12

describe g2

Answer 12

cels rest and make sure everything is ok - enough nutrients

Question 13

Describe phases of cell cycle

Answer 13

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.

Question 14

describe fission yeast

Answer 14

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

Question 15

describe budding yeast

Answer 15

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

Question 16

describe permissive low temp

Answer 16

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).

Question 17

describe at restrictive high temp

Answer 17

(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)

Question 18

describe low vs high temp

Answer 18

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

Question 19

describe low vs high temp when dividing

Answer 19

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

Question 20

describe low vs high temp when dividing AvsB

Answer 20

(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

Question 21

describe mature xenopus egg ready for fertilization

Answer 21

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

Question 22

describe frog egg

Answer 22

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

Question 23

describe frog egg - formal

Answer 23

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.

Question 24

describe studying cell cycle in cell free system- gen

Answer 24

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

Question 25

describe studying cell cycle in cell free system- formal

Answer 25

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.

Question 26

describe mammalian cells proliferating

Answer 26

cells in scanning electron micrograph = rat fibroblasts
diff than yeast which have round cells
mammalian = spindle shaped and long, lumps of cells = in mitosis

Question 27

describe tissue exposed to 3h thymidine - pic

Answer 27

going through s phase
triniated thymidine allows it be visualize

Question 28

describe tissue with immunofluorescence micrograph - pic

Answer 28

use labelled nts
can see how many cells in s phase
antibody staining brdu

Question 29

describe tissue exposed to 3h thymidine

Answer 29

(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.

Question 30

describe tissue with immunofluorescence micrograph

Answer 30

(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

Question 31

describe cytometer graph

Answer 31

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

Question 32

what is a flow cytometer

Answer 32

A flow cytometer, also called a
fluorescence-activated cell sorter, or FACS, can
also be used to sort cells according to their
fluorescence

Question 33

describe how cells stained in flow cytometer

Answer 33

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.

Question 34

what are the categories that flow cytometer shows - 3

Answer 34

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.

Question 35

describe distrubtion of cells - results of flow cytometer

Answer 35

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.

Question 36

describe cells and their phases and numbers = in flow cytometer

Answer 36

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