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104 Cards in this Set

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In meiosis, when do sister chromatids separate?
M2:anaphase
What is the main difference between mitotic and Meiotic II cell cycles?
M11 lacks an S phase during Interphase
Right after crossing over has occurred, what binds the maternal member of the pair to the paternal member?
chiasmata
How do cis double bonds in the lipid tails of membrane phospholipids affect membrane-relevant bonding?
there are fewer hydrophobic bonds in the membrane
Why do lipid rafts stick up above the membrane?
lipid tails are longer
What is likely to decrease the fluidity of a liver cell membrane?
increasing the length of lipid tails
What are the crossing over points often called?
chiasmas
What does the term “synapsis” refer to?
The zipping up of the two inner chromatids of a chromosome pair
Start kinase (and the checkpoint it overcomes) is present at the end of:
G1
When is DNA replicated?
S phase
What feature of the prokaryotic cell (not eukaryotic) allows them to withstand pressure?
cell wall
How does a membrane achieve stability?
creates a closed form
In TEM, what do polar head groups attract?
osmuim tetroxide..becoming dark
what does the flip flop mvmt across bilayer require?
flippases from ER
when someone says a lipid is saturated, what is it saturated with?
hydrogen
are physiological double bonds cis or trans?
ALWAYS cis
what determines membrane fluidity?
temperature,
# lipid tails w/ d-bonds
# d-bonds/tail
cholesterol
If you shorten the lipid tails of a membrane, how will membrane fluidity change?
increase
How does cholesterol affect membrane fluidity?
increases durability
reduces membrane fluidity
fits in spaces formed by d-bond kinks
How does saturation affect membrane fluidity?
more kinks (unsaturated) greater membrane fluidity
major proteins in RBC structure?
ankyrin
actin
spectrin
band 3 and glycophorin A
spherocytosis is caused by?
non-fxnl spectrin in RBC..RBCs swell and spleen gets clogged
rough face of membrane?
protoplasmic face
fxn of glycocalyx (neg charged)
protection
recognition
repulsion
what are centrosomes?
2 centrioles at right angles to each other
Microtubular Organizing Centers
replicated during Interphase
what occurs in interphase?
cell doubles in size and DNA content
restriction points occur where?
end of G1 to enter S
Identifying characteristics of prophase.
nuclear envelope and nucleolus begin to dissapear
chromosomes condense into 2 sister chromatids
centrioles migrate to opposite poles and form spindle fibers
Identifying characteristics of prometaphase.
nuclear envelope dissapears
kinetochores develop at centromeres and kinetochore MTs form
Identifying characteristics of metaphase
chromosomes align at equatorial plate
Identifying characteristics of anaphase
centromeres split and chromatids split apart
chromosomes move to opposite poles
Identifying characteristics of telophase
nuclear envelope reforms, nucleoli reappear, chromosomes disperse
d-cells formed by cytokinesis
Fxn of lamins and involvment in envelope breakdown.
provide structure to envelope
become phosphorylated by cdK, causing breakdown
upon de-phos and reassembly, lamin B reattaches to chromatin
what protein acts as the motor of the kinetochore pull?
dynein
also, movmt driven by microtubular assembly and disassembly
what is checked at the spindle checkpoint?
that chromosomes are attached to both centrosomes via kinetochore MTs and properly separating
the contractile ring that elicits cytokinesis is formed from what?
actin filaments, tightened by myosin 2
in meiosis, where does recombination take place?
prophase 1
Name some examples of cells that are static..have no cell cycle.
skeletal and cardiac muscle cells, nerve cells, RBCs
Name some examples of cells that are regenerative upon demand.
hepatocytes, fibroblasts
Name some examples of cells destined to divide frequently.
stem cells: spermatogonia, epithelial stem cells, hematopoieitic stem cells
Purpose of G1 phase.
cell grows
make proteins for S
Purpose of S phase.
DNA replication and chromosome duplication
Purpose of G2 phase.
Make proteins for size expansion and M phase.
How does a flow cytometer work?
measures amt of DNA in individual cells within a population by looking at the amount of fluorescence that binds to DNA.
what is a restriction point?
START: related to mitogen presence/deprivation. Mitogen is produced by GFs to get us to START. Once cell passes restriction point, it is IRREVERSIBLY committed to cell cyle progression
What are checkpoints?
STOP
Related to DNA damage and mitotic progression.
G1-S: DNA damage checkpoint
S:Did we replicate effectively?
G2-M:Did we finish DNA replication?
M: anaphase blocked if chromatids not properly aligned on spindle
Fxn of cylcins vs. CDks
cyclins: regulatory proteins of cylcin-CDk complex whose protein levels cycle during cell cycle
CDks: kinases that Phosphorylate cell cycle regulatory proteins
In which stage of the cell cycle is Cyclin D found?
only in G1
FXn of cyclin D
Required for passage through restriction point (start)
Made at start of G1
Degraded at end of G1
binds and activates CDK4.6
What does CDK4,6 require for activation?
cyclin D
Activation and production of cyclin D-Cdk4,6 results in production and activation of what?
cyclin E-Cdk2 to transition from G1-S
What are the 2 checkpoint cyclins for G1-S transition?
cyclin D and cyclin E
Explain action of pRb in early G1.
1. hypophosphorylated pRb inactivates E2F (transcription factor) by binding to it
2. cyclin D-Cdk4,6 phosphorylates pRb
3. pRb phosphorylation breaks up the pRb-E2F complex
4.E2F acts as a transcription factor and activates genes involved in S
5.G1-S
What induces gene transcription of Cdk4,6, cyclin D and E2F?
mitogen (growth factor) stimulation.
After cyclin D-Cdk4.6 phosphorylates and activates pRb, what does E2F stimulate the synthesis of?
itself, cyclin E, and Cdk2
Fxn of cyclin E-Cdk2.
further stimulates Rb phosphorylation releasing more E2F activity(+ feedback)
What binds and inhibits cyclin D-Cdk4,6?
INK4 (p16). Halting the restriction point passage
Involvment of p16 in non-proliferating cells
p16 active and attached to Cdk4/6 inhibiting expression of S phase genes
Involvement of p16 in proliferating cells?
p16 inactive, not attached to Cdk4.6. Expression of S phase genes activated
oncogene
a cancer inducing gene or a gene that transforms cells
proto-oncogene
normal cellular gene that upon alteration can aquire the ability to fxn as an oncogene Ex: Cyclin D
tumor suppressor protein
protein responsible for restraining cell proliferation, if altered may contribute to oncogenesis
Ex: p16, pRb (normally act as brakes)
Dx of Retinoblastoma
leukokoria (white pupil)
intralesional calcification
Dx age is 12 mo for those with bilateral tumor
Cause of Retinoblastoma?
mutation in pRb that is a tumor suppressor gene.
Most common primary intraocular malignancy in childhood
RB:1st hereditary cancer gene and first tumor suppressor gene to be cloned
Importance of pRb?
principal controller of the cell cycle in all human tissues
What happens when Retinoblastoma goes untreated?
untreated:tumors grow and produce seeding in the eye leading to RETINAL DETACHMENT, NECROSIS, and INVASION of ORBIT, optic nerve invasion and CNS invasion
Almost all untreated patients die of intracranial extension and disseminated disease w/n 2 yrs
most common tumors?
melanoma and pancreatic carcinoma
Involvment of p16 in non-proliferating cells
p16 active and attached to Cdk4/6 inhibiting expression of S phase genes
Involvement of p16 in proliferating cells?
p16 inactive, not attached to Cdk4.6. Expression of S phase genes activated
oncogene
a cancer inducing gene or a gene that transforms cells
proto-oncogene
normal cellular gene that upon alteration can aquire the ability to fxn as an oncogene Ex: Cyclin D
tumor suppressor protein
protein responsible for restraining cell proliferation, if altered may contribute to oncogenesis
Ex: p16, pRb (normally act as brakes)
Dx of Retinoblastoma
leukokoria (white pupil)
intralesional calcification
Dx age is 12 mo for those with bilateral tumor
Cause of Retinoblastoma?
mutation in pRb that is a tumor suppressor gene.
Most common primary intraocular malignancy in childhood
RB:1st hereditary cancer gene and first tumor suppressor gene to be cloned
Importance of pRb?
principal controller of the cell cycle in all human tissues
What happens when Retinoblastoma goes untreated?
untreated:tumors grow and produce seeding in the eye leading to RETINAL DETACHMENT, NECROSIS, and INVASION of ORBIT, optic nerve invasion and CNS invasion
Almost all untreated patients die of intracranial extension and disseminated disease w/n 2 yrs
most common tumors?
melanoma and pancreatic carcinoma
Loss of tumor suppressor protiens, p16 and pRb can lead to what?
oncogenesis
Overexpression of what can lead to oncogenesis?
Cyclin D (acts as a proto-oncogene)
Overexpression of Cyclin D can result in what?
Burkitt's lymphoma
Which protein is considered the Master Brake?
p53, tumor suppressor protein
mutations-oncogenesis
What is an example of a CIP (Cdk Inhibitory Protein) and what do they inhibit?
ex: p21
inhibit G1 and S Cyclin-Cdk complexes
How does DNA damage affect p21 and how?
if there is DNA damage, p53 is phosphorylated thus increasing in concentration. p53 then acts as a transcription factor increasing synthesis of p21. p21 inhibits Cdk/cyclin G1 and S complexes leading to CELL CYCLE ARREST
Besides arresting the cell cycle, what affect does p21 have on PCNA?
interacts with PCNA to inhibit DNA replication
Why do more than 50% of all cancers have a mutated p53?
b/c of the fact that p53 is a hetertetramer and it only takes 1 of 4 subunits to be mutated to inactivate the entire protein
How is a phosphodiester bond formed?
nucleophilic attack of 3'OH on sugar on alpha phosphate
How are nucleotide analogoes used to stop DNA chain elongation?
they lack the 3'OH therefore the chain can't grow (prevent viruses from growing out of control-treating HIV)
Features of B DNA
complementary
antiparallel
Neighboring bases of double helix are connected by what type of bonds?
Van der Walls
Strands of double helix are connected by what type of bond?
H-bond
What is most important in formation of dshelix?
varying hydrophobic bases
What is the DNA packaging problem?
each chromosome contains a single strand of dsDNA.
Barriers to packaging:
1. - charged
2. fxns as rigid rod
Problem solved by supercoiling
effect of supercoiling on free energy state?
reduces free energy state
Characteristics of R handed helix.
underwound
negative
*common form
What regulates supercoiling?
topoisomerases
Action of Quinolone antibiotics?
inhibit bacterial topoisomerases (DNA gyrase)
What is the simplest level of chromosome organization?
the nucleosome: dsDNA and histone proteins
Purpose of wrapping DNA around nucleosome?
protection from nuclease cleavage
Size of nucleosome ?
200 bp
Other names for polynucleosomes.
"beads on a string"
10nm fiber
When beads on a string wrap around each other what do they form?
30 nm fiber or SOLENOID
During which stage of the cell cycle is DNA most condensed?
metaphase: highest level of chromosomal structure
What is essential for segregation (movement) during cell division?
centromere. w/o centromere cannot attach to spindle
components of centromere?
short arm (p)
long arm (q)