Chapter 10 - PowerPoint Flashcards
What are the two types of nuclear division?
mitosis and meiosis
In mitosis are the daughter cells exact genetic copies of the parent cells?
yes
What are ploidy human cells?
diploid
What does diploid mean?
2 copies of each chromosomes, 2n
In meiosis how many divisions are there?
2
How many daughter cells are produced in meiosis?
4
What are the daughter cells of meiosis called?
gametes
What is haploid mean?
one copy, n
What is the master program of molecular checks and balences?
In mitosis, DNA is replicated and split evenly
What is the mitotic cytoskeleton do?
separates replicated DNA molecules precisely into the daughter cells
What are chromosomes made of?
DNA and proteins
What do proteins do in DNA?
stabilize, assist in packaging DNA during cell division, and influence the expression of individual genes
What shape are chromosomes in eukaryotes?
linear
What does histone proteins do?
compact DNA
What is chromatin?
DNA and all of its associated protiens
What is a nucleosome?
8-protein nucleosome core particle forms when DNA winds around the histones H2A, H2B, H3, and H4
What connects nucleosomes?
shorter liner segment of DNA
What are the histone proteins?
H2A, H2B, H3, and H4
How many of each histone proteins are in a nucleosome?
2
What is the first step of compaction
formation of nucleosomes
What charges does DNA have? why?
negative bc of phosphate groups
How wide is a nucleosomes?
10nm
How are nucleosomes further compacted? how big is it?
nucleosome and linker are bound by the fifth histone protein H1
30 nm
What is the difference between chromosomes and chromatin?
chromosomes are final form, everything else before this with proteins is chromatin
What does the solenoid model predict?
nucleosomes spiral helically
with about six nucleosomes per turn
Which chromatin is packed loosley?
euchromatin
Which chromatin is packed densly?
heterochromatin
Is euchromatin or heterochromatin regions more highly expressed?
euchromatin
What are Sister Chromatids
2 copies of the chromosome within the replicated chromosome
What are the sister chromatids held together by? where?
sister chromatid cohesion, at the center
What is cohesion
protein complex
Are homologous chromosomes identical?
nope
Are sister chromatids identical?
yes
What is ploidy?
The number of chromosome sets in a cell or species
What is a Karyotype?
Individual’s particular array of chromosomes.
How to prepare cells for a karyotypes?
- Add sample to culture medium that has stimulator for growth and division of cells (white blood cells in the case of blood). Incubate at 37oC.
- Stain the cells so that the chromosomes are distinguished.
- View the stained cells under a microscope equipped with a digital imaging
system and take a digital photograph.
What are the steps included in eukaryotic cell cycle?
G1, S, G2, M, C
What is the longest phase?
G1
What steps are in interphase?
G1, S, G2
What is G1?
Gap 1 Phase, where primary growth takes places, is the longest phase
Which is phase varies in length?
G1
What is a cell that stays in the G0 phase?
neuron
How long does it take for a cell to divide?
24 hrs
how long does the G1 phase take?
10 hrs
How long does the S phase take?
9 hrs
How long does the G2 phase take?
4 hrs
How long does the M phase take?
1 hr
What happens in the S (synthesis) phase?
replication of DNA
What happens in the G2 phase?
organelles replicate, microtubules organize
What are the 5 phases of mitosis?
prophase, prometaphase, metaphase, anaphase, telophase
What happens in cytokinesis?
separation of 2 new cells
Are human sex cells haploid or diploid?
haploid
What happens to the centrioles during mitosis?
they duplicate and divide
What is the main microtubule organizing center (MTOC)?
centrosome
Where do microtubules extend from?
centrosomes
What are asters?
starlike arrays formed from microtubules extending from the centersome
What happens to the nuclear envelope during interphase?
breaks down
In mitosis, at what stage do chromosomes first become visible with a light microscope?
prophase
Do asters exist in both plants and animal?
no, just animals
What are the 3 main things that occur in prophase?
1) spindle apparatus assembles (2 centersomes move to opposite poles forming spindle apparatus, and the formation of asters in animals)
2) nuclear envelope starts to disintegrate
3) nucleolus disappears
What phase do the centrioles duplicate?
S phase
When does prometaphase occur?
after nuclear envelope disassembles
Where do spindle micorotubles grow from? grow to?
grow from centrosomes at
opposite spindle poles toward the center of the cell
What is a kinetochores?
form on each sister chromatids at the the centromere
Where do kinetochore microtubules bind?
kinetochores
What are nonkinetochore microtubules?
overlap those from the opposite spindle pole
What is congression?
chromosomes begin to move to center of cell via assembly and disassembly of microtubules and motor proteins at kinetochores
What phase does congression occur?
preometaphase
What are the two type of spindles in mitosis?
kinetochores and nonkinetochores
What happens in metaphase?
spindle microtubules move chromosomes into alignment to the metaphase plate
What is anaphase?
centromeres split, removal of cohesion proteins, sister chromatins pulled apart via microtubules shortening
What are the two movements in anaphase?
anaphase A and anaphase B
What happens in anaphase A?
kinetochores pulled toward poles, disassemble microtubules into tublin subunits
What happens in anaphase B?
moves poles apart, nonkinetochore microtubules elongate the cell
What happens in telophase?
1) spindle apparatus disassembles
2) chromosomes decondense and uncoil
3) nuclear envelope forms around each set of sister
chromatids
4) nucleolus reappears
5) RNA transcription resumes
Do anaphase A and B occur at the same time?
yes
What happens in cytokinesis?
creates 2 daughter cells
How does cytokinesis occur in animals, protists, and many fungi?
furrow (contractile ring) girdles the cell and
deepens until it cuts the cytoplasm into two
parts
How does cytokinesis occur in plants?
cell plate forms between the daughter nuclei and grows laterally until it divides the cytoplasm in two
Where does mitosis occur in some other fungi and protists mitosis?
within the nucleus
What is the plane of cytoplasmic division is determined by?
layer of microtubules that persists at the
former spindle midpoint
What is the contractile ring made up of?
actin and myosin
Do the steps in mitosis occur exactly after each other?
no, some happens simultaneously, ie contractile ring starts to form before cytokinesis
In plant cytokinesis, what role do the vesicles play?
transport plant cell wall material to midline. produced from ER and golgi, and form the plasma membrane
What do the motor proteins do in anaphase B?
walk in opposite direction
What do nonkinetochore microtubules do in anaphase B?
push the pole apart by growing in length as they slide along
What is a common single-celled model?
Saccharomyces cerevisiae yeast
What did Saccharomyces cerevisiae yeast lead to the discovery of?
some genes that control the eukaryotic cell cycle
Why id Saccharomyces cerevisiae yeast a good model? (4)
◦ Many cells that can be easily visualized
◦ Cell cycle can be paused at a specific phase
◦ All cells can be synchronized at one phase
◦ Mutations are easily generated
What are the two irreversible points of the cell cycle?
1) Replication of genetic material (Between G1 and S)
2) Separation of the sister chromatids (2n –> 4n)
Where can the cell cycle be put on hold?
checkpoints
What are the two functions of checkpoints?
1) checked for accuracy and can be halted if there are errors
2) Allows cell to respond to internal and external signals
What are the three key checkpoints?
◦ G1/S checkpoint
◦ G2/M checkpoint
◦ Mitotic spindle checkpoint
What happens if a checkpoint is inactive?
cell cycle will proceed without stopping
What are the molecules responsible for checkpoints?
cyclins and cyclin-dependent kinases
What happens in the G1/S checkpoint?
◦ Cell “decides” to divide
◦ Primary point for external signal influence
What happens in the G2/M checkpoint?
◦ Cell makes a commitment to mitosis
◦ Assesses success of DNA replication
What happens in the Late metaphase (spindle) checkpoint?
Cell ensures that all chromosomes are attached to the spindle
Is the cell cycle under genetic control?
yes
Is the cell cycle a true cycle?
yes
What does true cycle mean?
its not reversible
Are genes transcribed during the cycle?
yes, transcribed needed before their products are needed
What are the significants of mutations affecting the cell cycle?
helped to identified the key regulatory pathways
What checkpoint is the main point in the cell cycle at which a cell decides whether to divide or not?
G1/S checkpoint
Why might the cell cycle stop at G1/S checkpoint?
DNA is damaged by radiation or chemicals. Also if the cell is nutritionally deficient or growth factors are absent.
What is the checkpoint where the cell commits to mitosis?
G2/M
Why might the cell stop at the G2/M checkpoint?
if DNA was not replicated accurately in S or if the DNA has been damaged by radiation or chemicals
What are cyclins and cyclin-dependent kinases made up of?
proteins
When are cdks active?
when it is bound to cyclin
What is kinases?
enzymes
Do the concentration of cyclins change over the cell cycle?
yes
When does the mitotic spindle checkpoint occur?
before metaphase in the M phase
What happens when a cell begins anaphase?
it is irreversibly committed to completing M
What are the 3 classes of cyclins?
G1/S cyclin, S cyclin, and M cyclin
What is the role of G1/S cyclin?
required for transition from G1 to S, and to
commit to DNA replication
What does the G1/S cyclin bind to? at what time?
Cdk2 near the end of G1
What is the role of S cyclin?
required for initiation of DNA replication and progression
of the cell through S
What does the S cyclin bind to? at what time?
binds to Cdk2 in the S phase
What is the role of M cyclin?
required for the transition from G2 to M, and the progression of the cell through mitosis
What does the M cyclin bind to? at what time?
M cyclin binds to Cdk1 in G2
What does the fourth class of cyclins ( G1 cyclin) binds to? at what time? Cdk4 and Cdk6 before the G1 /S transition
Cdk4 and Cdk6 before the G1 /S transition
What does the fourth class of cyclins ( G1 cyclin) form? function?
form two cyclin–Cdk complexes
needed to move the cell through the G1 checkpoint and proceed from G1 to S
What is the M cyclin-Cdk1 complex is also called?
M phase-promoting factor (MPF)
What happens to the MPF when the chromosomes are correctly attached to the mitotic spindle
MPF activates another enzyme complex, the anaphase-promoting complex (APC)
What happens when activated APC degrades an inhibitor of anaphase?
separation of sister chromatids
What does APC direct the degradation of? what does this lead to?
M cyclin, causing Cdk1 to lose its activity
What are the roles of Cdks? (3)
1) phosphorylate proteins
2) Primary mechanism of cell cycle control
3) Cdks partner with different cyclins at different points in the cell cycle
What was the previous viewpoint of cyclins?
cyclins drove the cell cycle
What is the current viewpoint of cycline? Where is this talked about?
Cdk itself is also controlled by phosphorylation (( talks about the discovery of M cyclin-CDK complex)
What was Johnson and Rao’s experiment?
They fused human HeLa cells at different stages of the cell cycle. Cell fusion produces a single cell with two separate nuclei. The researchers allowed the fused cells to grow and determined whether one nucleus influenced the other in terms of progression through
the cell cycle
What were the results of Johnson and Rao’s experiment?
DNA synthesis quickly began in the original G1 nucleus. Normally, the G1 nucleus would
not have initiated DNA synthesis until it reached S phase itself, which could have been several
hours later. The result suggested that one or more Molecules that activate S phase are present
in the cytoplasm of S phase cells
found cyclins and cdks (groundwork for, didn’t know what they were but discovered their affects)
What are internal controls modified by?
external controls
What are some examples of external controls
peptide hormones and growth factors
What do hormones and growth factors act on the cell by?
reception-transduction-response pattern
What happens to the reaction when it is triggered by the activated receptor?
may speed, slow, or stop the progress of cell division
What is Contact inhibition? What phase will the cells enter?
stops the cell cycle b/c there are no is no room for division, will enter G0 phase
Are cancer cells affected by contact inhibition?
no, they will keep dividing
What does metastasis?
cancer cells lose adhesions to other cells and spread throughout the body
What are oncogenes?
mutated form of these genes which encode altered versions of these products
What does onco mean?
cancer causing
What were they trying to find out in the Gorbsky experiment?
How do the chromosomes moves towards the poles?
What was the hypothesis for the Gorbsky experiment?
The kinetochore microtubules moved pulling the chromosome towards the poles OR chromosomes
moved by sliding over or along the kinetochore microtubules.
What was the set up for the Gorbsky experiment?
Bleached segment of kinetochores and watched what happened
What was the result for the Gorbsky experiment?
support the hypothesis that chromosomes move
by sliding over or along kinetochore microtubules.
how did mitosis evolve from binary fission?
Scientists believe that the ancestral division process was binary fission and that mitosis evolved from that process
Does the cyclin bind to another protein? Name the protein.
Yes, cdk
Does the other protein need the cyclin to work?
yes
When Cyclin E and the other protein (Name?) form a complex, does the cell move through the cell cycle? Name the phases
cdk, G —> S
What type of cyclin is cyclin E?
G1/S cyclin
