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Biomed > week 9 > Flashcards

week 9 Flashcards

1
Q

interphase (90% of the cell cycle) is divided into subphases (4)

A

G1 - 1st gap
S - synthesis
G2 - 2nd gap
G0 - resting phase

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2
Q

what happens in G1

A

first gap phase

  • prep phase prior to cell entering DNA synthesis phase
    - requires nutrients and growth factors
  • RNA protein, lipid and carb synthesis

many organelles are duplicated (NOT dna yet)
duration - variable

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3
Q

what happens in S phase

A
  • DNA and chromosomal protein synthesis occurs

duration- approx 7-8 hours in a typical mammalian cell with a 16 hour cycle

cell is now committed to cell division
- no growth factors needed
- DNA replication occurs here creating 2 identical daughter genomes

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4
Q

what happens in G2

A

second growth phase
- interval between DNA synthesis and mitosis
- enzyme, protein and ATP synthesis occurs

duration - lasts aprox 3 hours

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5
Q

what happens in M phase

A
  • mitotic phase

Cell undergoes mitosis and then cytokinesis

duration 1-2 hours

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6
Q

what happens in G0

A
  • State of withdrawal from cell cycle
    -Cell is neither dividing nor preparing to divide
  • Instead, the cell is “doing its job” - performing it’s
    function within the tissue
  • Common for differentiated cells
  • Examples of cells in G0:
  • Hepatocytes, neurons
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7
Q

what are the three features of biochemical switches

A
  1. Generally binary (on/off) to launch an event in a
    complete & irreversible fashion
  2. Robust & reliable
    * Contains back up mechanisms to ensure efficacy under
    variable conditions & if some components fail
  3. Adaptable & modified to suit specific cell types
    • Responds to specific intracellular or extracellular signals
    • Cyclin dependent kinases (Cdks) – more to come
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8
Q

what are the checkpoints / transitions in the cell cycle

A

Points in the eukaryotic cell division cycle where
progress through the cycle can be halted until conditions
are suitable for the cell to proceed to the next stage

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9
Q

what are the major regulatory transitions in the cell cycle checkpoints

A
  1. Start Transition (aka G1/S)
  2. G2/M transition
  3. Metaphase-to-anaphase transition (aka M-to-A)
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10
Q

what is the rate limiting and committing step of the cell cycle

A

G1/S

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11
Q

what is the key cell cycle control system

A

cyclin dependant kinases

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12
Q

cdks are responsible for ……. in ….. of intracellular proteins that initate/regulate the major events of the cell cycle

A

cyclical changes
phosphorylation

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13
Q

Cdks are controlled by a group of proteins called

A

cyclins

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14
Q

cyclical changes in cyclin protein levels result in the cyclic assembly and activation of ……… at specific stages of the cell cycle

A

cyclin cdk complexes

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15
Q

what are the 4 classes of cyclins that form specific complexes with Cdks

A
  1. G1 cyclins : D cyclin
  2. G1.S cyclins : Cyclin E
  3. S- cyclins : cyclin A
  4. M cyclins : Cyclin B
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16
Q

G1 cyclins : D cyclin

A
  • forms complex with Cdk4 or Cdk 6
  • involved in G1 phase of the cell cycle, needed for initiation of transcription of G1/S cyclins to help promote passage through start transition
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17
Q

G1.S cyclins : Cyclin E

A
  • forms a complex with Cdk2
  • bind Cdks at the end of G1 and help trigger progression through the start transition
  • levles decrease in S phase
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18
Q

S- cyclins : cyclin A

A
  • forms complex with Cdk1 and Cdk2
  • bind cdks after progression through start transition and helps timulate chromosome duplication during S phase
  • levels remain evela
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19
Q
  1. M cyclins : Cyclin B
A
  • forms complex with Cdk1
  • binds Csks to stimulate entry into mitosis at the G2/M transition
  • levels decrease in mid mitosis
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20
Q

how do cyclin Cdk complexes work

A

Cyclin protein does not simply activate its Cdk partner, but also directs it to a specific target protein

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21
Q

APC/C is the

A

anaphase promoting complex

aka cyclosome

  • Member of ubiquitin ligase family of enzymes (labeling for destruction in proteasomes)
  • Used to stimulate proteolytic destruction of specific regulatory proteins

Target proteins: securin, M-cyclins, S-cyclins

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22
Q

Growth factors are required in the …. phase

A

G1

Growth factors bind to specific receptors to
stimulate cellular growth and proliferation

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23
Q

Early response genes are

A

usually transcription factors
activated by OA

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24
Q

Delayed response genes are

A

usually Cdks, cyclins, or other proteins needed for cell division

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25
Q

in response to binding a growth factor …….

A

Cyclin D and then E are transcribed and translated

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26
Q

Cyclin D can form complexes with

A

Cdk4 and Cdk 6
- Call the G1-cdk complex

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27
Q

Cyclin E can form complexes with Cdk2

A

Called the G1/S-cdk complex

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28
Q

Active G1-cdk and G1/S-cdk complexes allows

A

progression through the start checkpoint

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29
Q

Active G1-cdk (and G1/S-cdk)
complex will target a protein
called

A

RB and phosphorylate
it.

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30
Q

RB functions as a

A

a transcription co-repressor

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31
Q

Hyperphosphorylation of RB will

A

inactivate RB

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32
Q

Inactive RB then releases a transcription factor ….

A

E2F,
allowing transcription to proceed

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33
Q

In early S phase, cyclin D (G1-cdk complex) and E
(G1/S-cdk complex) are

A

targeted for destruction

This also promotes progression through the S phase of the cell cycle

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34
Q

Active S-cdk complex allows progression through

A

the S phase of the cell cycle

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35
Q

What was the S-cdk complex?

A

cyclin A

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36
Q

What is occurring during the S phase of the cell cycle?

A

synthesis of DNA

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37
Q

during G2

A
  • S-Cdk complex levels are still high in G2
    -* M-cyclin levels begin to rise
    - Form a M-Cdk complex
    M-Cdk complex is needed to pass through the G2/M
    checkpoint

At the end of G2, the S-cyclins are destroyed

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38
Q

We need to be able to control the activity of Mcyclins so that

A

mitosis doesn’t start too soon

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39
Q

Once the M-Cdk complex is assembled, it is

A

immediately
inhibited via phosphorylation

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40
Q

When the cell is ready for mitosis to begin, the M-Cdk
complex is

A

de-phosphorylated

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41
Q

Before progressing to anaphase and then to telophase, we reach our final checkpoint

A

Metaphase-to-anaphase (M-to-A)
checkpoint

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42
Q

in the metaphase to anaphase checkpoint Instead of a cyclin-cdk complex being used to
progress through the M-to-A checkpoint, instead we
used

A

regulated proteolysis

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43
Q

APC/C complex targets a protein called …… by
ubiquitylation for destruction by a proteosome

A

securin

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44
Q

Securin is an …..
that protects protein linkages that
hold …..
together in early mitosis

A

inhibitory protein
sister chromatin pairs

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45
Q

Destruction of securin activates a …… that separates the sister
chromatids allowing progression
to ….

A

protease
anaphase

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46
Q

At the end of mitosis, the M-cyclins are also
targeted for …..

A

destruction by APC/C

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47
Q

Destroying these cyclin APC/C inactivates most …. in cell

Then, many proteins phosphorylated by ….from S
phase to early mitosis are ……by
various ….. in the anaphase cell

A

Cdks
Cdks
dephosphorylated
phosphatases

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48
Q

In unfavourable conditions, the cell cycle can be paused
at any of the main checkpoints, what checkpoints?

A

progession through G1
entry into M
progression through M to A

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49
Q

Progression through G1 is delayed if:

A
  • DNA is damaged by radiation, chemicals, or errors
  • Absence of nutrients or growth factors
  • Abnormal cell size
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50
Q

Entry into M is prevented when

A
  • DNA replication is not complete
  • Presence of DNA damage
  • Abnormal cell size
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51
Q

Progression through M-to-A is prevented if

A

Chromosomes are not properly attached to mitotic spindle

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52
Q

what is CKI

A

binding of cdk inhibitory protein

  • inactivates cyclin Cdk complex
  • binding stimulates rearrangement in structure of Cdk active site
  • primarily used by cells to govern the activities of G1/S and D-cdks early in the cell cycle
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53
Q

what are the three important CKIs

A

p16 inhibits

p21 inhibits

p27 inhibits

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54
Q

p16 inhibits

A
  • CyclinD-cdk4 & CyclinD-cdk5 (G1-cdk complex)
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55
Q

p21 inhibits

A

-CyclinE-cdk2 (G1/S-cdk complex)
- CyclinA-cdk2 & CyclinA-cdk1 (S-cdk complex)
-Cyclin B-cdk1 (M-cdk complex)

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56
Q

p27 inhibits

A
  • CyclinA-cdk2 & CyclinA-cdk1 (S-cdk complex)
  • CyclinE-cdk2 (G1/S-cdk complex)
  • Cyclin B-cdk1 (M-cdk complex
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57
Q

what are the two main tumour suppressor genes

A

p53
RB

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58
Q

what does p53 recognize

A
  • Recognizes and binds damaged
    DNA
  • Unstressed cells have lower levels of p53 since it will be bound by a protein called Mdm2 and be
    degraded
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59
Q

what does RB recognize

A

Generally found in active form
* Can also recognize damaged DNA

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60
Q

In the presence of DNA damage, p53 will be
phosphorylated, releasing ……
p53 will not be ….

A

Mdm2
degraded

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61
Q

Active p53 binds DNA
and promotes the
transcription of …

A

p21

p21 binds the G1/S-cdk
complex, inhibiting it.

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62
Q

An inactive G1/S-cdk
complex will pause
the cell cycle at the
__?__ transition

A
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63
Q

RB in the presence of a growth suppressor signal or DNA damage

A

p16 is transcribed; p16
inhibits the G1-cdk complex,
which was needed to
inactivate RB

RB remains activated and
bound to E2F
- * No transcription of G1/S- cyclins or S-cyclins
- * Cell cycle is paused at start transition

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64
Q

what is contact inhibition

A

The cell cycle progression can
also be inhibited due to contact with:
other cells
- density dependant
inhibition
a basement membrane or other matrix component
- anchorage
dependance
*** regulated with cadherins and Beta-catenin
pathway

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65
Q

describe PI3K-Akt-mTOR C pathway in the cell cycle

A

Akt can promote cell cycle progression by:
* Akt activates/increases:

Cyclin A —> activation of CDK-1
Cyclin D ——> activation of CDK-4/6

Akt decreases/inactivates:
- p21 and p27

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66
Q

what are the three types of point mutation

A

substitution
insertion
deletion

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67
Q

substitutions can be

A

transitions (A , G or C,T) and transversions (purine for pyrimidine bases

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68
Q

Insertions or deletions of single nucleotides can lead to

A

frameshift mutations – all of the triplets are off by one

These are often called “frame-shifting indels”
* Often results in total loss of function of the protein:
▪ “O” blood type results from a frameshift mutation and
loss of function of the red blood cell antigen
▪ Tay-Sachs disease

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69
Q

If a multiple of three nucleotides are inserted or deleted, then the

A

reading frame is preserved

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70
Q

One nucleotide deletion
frameshift

A

Protein is no longer
functional

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71
Q

Three nucleotide deletion –
non-frameshift, but

A

loss of an
amino acid

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72
Q

what are the two types of point mutations

A

silent or conservative missense
nonconservative missense

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73
Q

what is an example of non conservative missense

A

sickle cell anemia

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74
Q

what does the sickle cell anemia surprisingly protect against

A

malaria

-RBCs that have some sickle-cell hemoglobin are not good hosts for the parasite that causes sickle cell disease –
thus the trait (heterozygote patient) is protective
▪ However, the homozygote (all hemoglobin
is sickle-cell hemoglobin) is more vulnerable to the disease than rest of the
population

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75
Q

mendelian disorders

A

Due to mutations in single genes that have large
effects

Most of these have relatively small effects on phenotype

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76
Q

Penetrance

A

how likely the mutated gene is to be expressed

So, if something is autosomal dominant but has a 50% penetrance, a heterozygote may only have a 50% chance of showing the disease phenotype

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77
Q

Disorders due to insufficient production of an enzyme
tend to be recessive

A

enzymes are specific therefore tend to be more severe

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78
Q

what is Marfan syndrome

A
  • disorder of connective tissues, manifested
    principally by changes in the skeleton, eyes, and cardiovascular system

-Epidemiology: prevalence of 1 in 5000

  • Etiology:
    ▪ Disorder due to a defect in gene for fibrillin-1
  • 75 – 85% are familial; the rest are new mutations
  • Autosomal dominant
    ▪ chromosome 15
    ▪ 600 distinct mutations – most are missense
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79
Q

what is the Pathophysiology of Marfan syndrome

A

▪ Fibrillin is an important component of elastic connective
tissue, provides a “scaffold” for elastic fibre deposition
▪ Loss of fibrillin-1 explains many findings
* i.e. aneurysm formation, ligamentous laxity, defects in
eye structure
* Others are more difficult to explain
* Thought that increased skeletal growth is due to
increased bioavailability of TGF-beta, which is affected
by fibrillin levels (TGF-beta can also impact smooth
muscle development)

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80
Q

what are the Clinical findings of Marfan syndrome

A

Tall, with very long extremities and lax ligaments
▪ Dislocation of the lens
▪ Cardiovascular changes:
* Mitral valve prolapse – malformed and “weak” heart
valve
* Weakness in the muscular layers of the aorta, which
can lead to aortic valvular incompetence and
development of serious aneurysms
▪ Variable expressivity – some individuals may be lacking
certain clinical findings
* i.e. skeletal findings with no ocular findings
* Prognosis: Variable, main cause of mortality and morbidity are
aneurysms and valvular defects
▪ Surgical repair of aneurysms, heart valves

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81
Q

Autosomal recessive disorders

A

Largest category of Mendelian disorders

The expression of the defect tends to be more uniform than in
autosomal dominant disorders.
▪ Complete penetrance is common.
▪ Onset is frequently early in life.
▪ Although new mutations associated with recessive disorders do
occur, they are rarely detected clinically, since the individual with
a new mutation is an asymptomatic heterozygote
▪ Many of the mutated genes encode enzymes
* In heterozygotes, equal amounts of normal and defective enzyme
are synthesized
* Usually the natural “margin of safety” ensures that cells with half
the usual complement of the enzyme function normally

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82
Q

Consequences of Enzyme Defects

A

Accumulation of a substrate
Blockade of a metabolic pathway
Failure to inactivate another enzyme or substrate

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83
Q

Lysosomal storage diseases

A

Lysosomal storage disorders can be from a range of
problems with lysosomal enzymes:
▪ Lack of the enzyme, leading up to a build-up of a
substrate within a cell that is toxic
▪ Misfolding of the lysosomal enzyme
▪ Lack of a protein “activator” that binds to the substrate
and improves the ability of the enzyme to act on it

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84
Q

Pathophysiogy of lysosomal storage diseases

A
  • In the example shown, a complex
    substrate is normally degraded by a
    series of lysosomal enzymes (A, B,
    and C) into soluble end products
  • deficiency or malfunction of one of
    the enzymes (e.g., B) → incomplete
    catabolism → insoluble
    intermediates that accumulate in
    the lysosomes → “primary
    storage” problem
    ▪ huge, numerous lysosomes
    interfere with cellular function
  • secondary storage problem = toxic
    effects from defective autophagy
    ▪ autophagy = “cellular
    housecleaning”
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85
Q

Gaucher Disease

A
  • Most common lysosomal storage disease
    ▪ Between 1 in 20,000 and 1 in 40,000 live births
    ▪ Autosomal recessive inheritance
  • Defect in the gene for glucocerebrosidase
    ▪ Enzyme cleaves the
  • glucose residues from ceramide, found in cell membranes
  • glucosylceramide accumulates in lysosomes
    ▪ Metabolites accumulate mainly within macrophages and
    other phagocytic cells as they phagocytose dying cells
    and metabolize the membranes
  • This can lead to the activation or loss of function of the
    phagocytes
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86
Q

Gaucher Disease type 1 vs type 2

A

Type I – involves organs outside the
central nervous system – 99% of cases
▪ Findings are mostly within the spleen
and bone
* Enlargement of the spleen and liver
* Weakened bones → frequent
fractures
▪ Often relatively mild course

  • Type II – involves the CNS as well as
    other organs
    ▪ Hepatosplenomegaly and rapid
    neurological deterioration, with
    death in early childhood
    ▪ CNS macrophage activation →
    production of toxic signals by
    macrophages → neuronal death
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87
Q

An affected male does not transmit the disorder to his
….., but all …. are carriers.

A

sons
daughters

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88
Q

Sons of heterozygous women have a … in …. chance of receiving the mutant gene

A

1 in 2

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89
Q

A male with a mutant allele on his single X chromosome is ……..

A

= hemizygous for the allele

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90
Q

X-linked recessive inheritance is

A

transmitted by healthy heterozygous female carriers to affected males

affected males to their obligate carrier daughters

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91
Q

Hemophilia A is the

A

Loss of function of a coagulation factor necessary
for clotting

▪ Affects over 20,000 men in North America
▪ Different mutations confer different bleeding risk –
thousands of mutations have been identified with
variable impacts on coagulation

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92
Q

clinical features of hemophilia A

A

▪ Bruising and prolonged bleeding with minimal trauma
▪ Mucosal bleeding, hematomas in joint spaces
(hemarthrosis)

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93
Q

proband

A

The person being “examined” (usually the one with a genetic condition)

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94
Q

Position of the proband in the family tree is indicated by

A

an arrow

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95
Q

A complete family history is then taken “centered”
around the

A

proband

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96
Q

autosomal dominant in a pedigree

A
  • Frequent
    appearance of
    the disease
    throughout
    generations

may not show
typical 50%
chance of
transmission
(remember
reduced
penetrance)

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97
Q

autosomal recessive in a pedigree

A

The risk of
autosomal
recessive
disorders
manifesting
increases if there
is consanguinity

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98
Q

X-linked recessive in a pedigree

A

Only males appear affected

Trait is never passed from
father to son

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99
Q

DNA replication happens during what phase

A

S

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100
Q

each daughter strand cell will inherit a …… containing ….. and …..

A

DNA double helix
1 original strand
1 new strand

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101
Q

DNA four main steps

A

strand separation
primer creation
DNA replication
primer removal

102
Q

what two protiens are needed to open up the DNA helix

A

DNA helicase
single stranded binding proteins

103
Q

what bonds do DNA helicase break

A

H bonds between complimentary base pairs

104
Q

what is the purpose of single stranded binding pairs

A

stablility

105
Q

what are the two limitations of DNA polymerase

A

DNA polymerase can only add nucleotides to an existing strand of DNA
only works in 5- 3 prime direction

106
Q

what will a primer be used for DNA polymerase ?

A

serves as a base paired chain on which to add new nucleotides

107
Q

leading strands are synthesized

A

continuously

108
Q

the lagging strand is synthesized

A

discontinuously

  • direction of polymerization is opposite to chain growth
109
Q

how many primers do we need for lagging strands

A

one for each okazaki fragment

110
Q

RNA primers are removed by

A

DNA repair system and then are replaced with DNA

111
Q

DNA ligase …

A

joins the 3’ end of the new DNA fragment with the 5’ end of the previous fragment

seals the gap

112
Q

what fixes supercoiling

A

DNA topoisomerase

  • breaks phosphodiester bonds
  • allows DNA to rotate freely
  • bonds will reform as the enzyme leaves
113
Q

in addition to DNa replication, …. must also be synthesized so that newly replicated DNA can be packaged into nucleosomes

A

histones

114
Q

histone synthesis happens during what phase of the cell cycle

A

S

115
Q

what is the DNA polymerase activity

A
  • takes place prior to a new nucleotide being covalently added to the growing daughter chain
  • correct nucleotide has a higher affinity for the DNA polymerae than an incorrect nucleotide
  • more energetically favourable to add the correct nucleotide
116
Q

what is exonuceolitic proofreading

A

occurs right after an incorrect nucleotide has been covalently added to a growing daughter chain

  • will not provide an effective 3’OH end for the DNA polymerase to add on the next nucleotide
  • separate catalytic site on DNA polymerase will initate DNA polymerase to move in a 3’ to 5’ direction, clipping off any unpaired or mispaired residues

using proofreading exonuclease

117
Q

what are telomeres

A

specialized nucleotide sequences at the end of the chromosome

  • many tandem repeats
118
Q

what are telomere sequences recognized by

A

telomerse
- can replenish sequences each time a cell divides
- activity of telomerase varies based on the cell type

119
Q

replicative cell senescence

A

cell has withdrawn from the cell cycle and is no longer dividing

120
Q

telomerase recogonized the … of an exisiting ……. repeat on the parent strand and will ….. it in the …. direction

A

tip
telomere DNA
elongate
5’ to 3’

121
Q

what does telomerase use as a template

A

RNA template

  • reverse transcriptase
122
Q

what is a centrosome

A
  • protein organelle
  • consists of a pair of centrioles surrounded by a cloud or amorphous material
  • undergo replication in preparation for mitosis
123
Q

in prometaphase

A
  • nuclear envelope breaks down
  • chromosomes attach to spindle microtubules via a protein called a kinetochore
124
Q

in metaphase

A
  • chromosomes will align at the equator of the cell
  • kinetochore microtubules attach to sister chromatics to opposite poles of the spindle
125
Q

in anaphase

A
  • chromatids synchronously separate forming two daughter chromosomes
  • kinetochore microtubules get shorter while spindle pole moves apart
126
Q

in telophase/cytokinesis

A
  • daughter chromosomes arrive at poles of spindle
  • chromosomes decondensce and a new nuclear envelope reassembles around each set
127
Q

cytokinesis is when

A

the membranes separate

128
Q

in G1 the number of chromosomes is

A

2n

129
Q

in prophase the number of chromosomes is

A

2n

130
Q

in cytokiesis the number of chromosomes

A

2n

131
Q

what is neoplasia

A

new growth
aka tumour

132
Q

neoplasm

A

abnormal mass of tissue
- uncoordinated and excessive growth
- continues beyond cessation of growth stimuli

133
Q

what does benign mean

A

remains localized

134
Q

what is maligment

A

moves and invades various tissue

135
Q

the ending of “oma” is

A

often denotes a benign tumour

eg. lipoma , adeoma

136
Q

what does suffix carcinoma mean

A

malignant tumour of epithelial cell

137
Q

what does the suffix sarcoma mean

A

malignant tumour of mesofermal . mesenchymal origin
muscle, cartilage and bone

138
Q

what are two key factors for tumour differenetiation

A

morphological and functional

139
Q

what is the difference between well differentiated and poorly differentiated

A

well differentiated, very different looking

139
Q

pleomorphism is

A

cells that vary in size and shape

139
Q

why is age a risk factor in cancer

A

accumulations of somatic mutations that accompanies aging of cells

a decline in immune competence may also play a role

140
Q

anaplasia is …

A

poorly differentiated
- pleomorphism
- abnormal nuclear morphology
- nuclei disproportionally large
- presence of a large numbers and abnormal mitoses
- loss of cell polarity

140
Q

why is chronic inflammation a risk factor for cancer

A

tissue damage
cell proliferation must occur to repair damage
activated immune cells to produce reactive oxygen species that can damage DNA

inflammatory mediators produced can promote cell survival

140
Q

in addition to anaplasia, malignant tumours will often show

A

-ischemic necrosis (lack of blood supply, grown so quickly with not enough blood)
- areas of hemorrhage
- local invasion
(lack a capsule)
- metastasis (migration to distant tissues via lymphatics or blood vessels)

140
Q

what are some acquired conditions that increase the risk of cancer

A

chronic inflammatory disorders
precursor lesions
immunodeficiency states

140
Q

why are precursor lesions a risk factor for cancer

A

localized morphologic changes in epithelial tissue that increase the risk of malignant transformation

(hyperplasia, metaplasia, dysplasia)

141
Q

what is hyperplasia

A

increase in number of normal cells

142
Q

what is metaplasia

A

replacement of one differentiated somatic cells with another

  • occurs in response to chronic irritation so that cells can better withstand the stress
  • occurs due to reprogramming of stem cells or undifferentiated mesenchymal cells found in connective tissues
143
Q

what is dysplasia

A

presence of abnormal cells

144
Q

why are immunodeficient patients at an increased risk for cancer

A

they have a higher than normal incidence of chronic infection from viruses

145
Q

repeated rounds of cell replication creates a …… the higher likehood of accumulating mutations resulting in malignancy

A

fertile ground for development of malignant tumours

146
Q

what are the three types od mutations

A

initiating
driver
passanger

147
Q

what is an initiating mutation

A

found in all progeny, begins
the process towards malignant transformation

Essentially the first driver mutation
- Often include loss-of-function mutations in genes that maintain genomic integrity
* Leading to genomic instability

148
Q

what is a driver mutation

A

mutation that increases
malignant potential of the cell

149
Q

what is a passanger mutation

A

mutation with low malignant
effect

150
Q

what are the classes of mutated genes in driver mutations

A

proto-oncogenes
tumour supressor genes
genes regulating apoptosis
genes responsible for DNA repair

151
Q

what is a proto oncogene

A
  • gain of function mutations => oncogenes

promote excessive cell growth
- created by mutations

  • can include growth factors for their receptors, signal transducers, transcription factors or cell cycle components
152
Q

what are tumour suppressor genes

A
  • generally loss of
    function mutations
153
Q

are genes regualting apoptosis

A

can be gain or loss of
a function

154
Q

what do genes responsible for DNA repair do?

A
  • generally loss of
    function
    - affected cells aquire
    mutations at an
    accelerated rate
155
Q

tumour progression once established, tumours evolve …… based on …….. of the fittest

A

genetically
survival/selection

mutations occur at random

156
Q

Tumour subclones have to compete for

A

access to nutrients

best at accessing nutrients remain in tumour = more aggressive tumour

157
Q

onco genes can turn on … without growth promoting signals

A

proliferation

158
Q

Ras in oncogenes

A
  • Downstream component of receptor tyrosine kinases
    signaling pathways
  • tyrosine then activates Ras
  • Ras activates MAP kinase
  • Map kinase activates Mek
  • Point mutation of RAS family genes is the single most common abnormality of proto-oncogenes in human tumors
  • downstream signaler for lots of growth factors
  • EGF, PDGF, and CSF-1
159
Q

proto onco genes are …… but when mutated are named …

A

present in healthy cells

oncogenes

160
Q

PI3K in oncogenes

A
  • common in certain cancers
  • promotes cell proliferation
  • inhibits apoptosis

PI3K in healthy cell receives signal and activates and works downstream to activate Akt
(Akt activates cyclin A and D and decreases/ inactivates p21 and p27)

161
Q

Myc in oncogenes
what is it?
what happens when Myc is induced and activated?

A

MYC is a transcription factor
- IMMEDIATE early response gene

INDUCED BY - Ras/MAPK
- stimulates transcription
of CDKs

WHEN ACTIVATED
- increases cell proliferation and growth

  • increased telomerase activity
  • May also allow more terminally differentiated cells to gain characteristics of stem cells
162
Q

what is the warburg effect

A

glycolytic enzymes are up- regulated

chooses the lactate to pyruvate even though there is oxygen

163
Q

Cdks and cyclins in oncogenes

A
  • most important checkpoint is G1/S
    - if you can get it going
    rapidly, there is more
    success
164
Q

tumour suppressor genes apply …… to cell proligeration

A

the brakes

165
Q

abnormalities in tumour supressor genes lead to …..

A

failure of growth inhibition

166
Q

many such as RB and p53 recognize genotoxic stress resulting in

A
  • shutting down proliferation
  • Activation of oncogenes aren’t enough for cancer
    induction, usually requires loss of tumour suppressor
    genes as well
167
Q

what is the enabler of genomic stablity

A

TP53
- cell cycle arrest and apoptosis in result of DNA damage

168
Q

what are the two main inhibitors of cell cycle progression

A

Rb
(inhibitor of G1/S transition)
CDKN2A
(p16 negative regulator of cyclin dependant kinases)

169
Q

hypophosphorylated RB

A

releases E2F
more G1s2 complex is synthesized in favourable conditions

170
Q

what form do we usually find Rb in a quiescent cell

A

hypophosphorylated

(hugging of E2F)

ACTIVATED FORM

171
Q

what form is RB in to facilitate passing through the G1/S checkpoint

A

hyperphosphorylated

172
Q

what is direct loss of function of Rb

A

loss of function involving both RB alleles

173
Q

what is the indirect loss of function of RB

A
  • Gain of function mutation upregulating CDK4 /cyclin D
  • Loss of function mutation of CKIs (p16)
174
Q

TP52 codes for

A

is the actual gene that codes for : p53
- regulates cell progression, DNA repair, cellular senescence and apoptosis

Most frequently mutated gene in human cancer

175
Q

p53 functions in the presence of

A

DNA damage

  • stimulates DNA repair

if DNA is repaired -> cell cycle can resume
if DNA repair fails -> p53 will activate pro-apoptosis pathways

176
Q

what does p53 induce

A

p21
- can shut down checkpoints in the cell cycle

177
Q

is mdm2 is mutated what does it do

A

it hugs p53 and inhibits it

178
Q

what is senescence in a cell

A

permanently exited the cell cycle and never divides again

179
Q

With loss of p53,

A

DNA damage goes
unrepaired & driver
mutations
accumulate in
oncogenes & other
cancer genes —>
malignant
transformation

180
Q

what would happen if there was a mutation of p16

A

Acquired mutations detected in many cancers

can also be silenced by hypermethylation rather than mutation

Inhibits Cdk4-
Cyclin D complex (G1-
cdk complex) needed for
progression through the cell
cycle

181
Q

At least 1 of the 4 key regulators of the cell cycle is
dysregulated in the significant majority of all human cancers

what are the 4?

A

p16, cyclin D, Cdk4, RB

182
Q

APC in tumour surpressor genes

A
  • Very commonly
    mutated in colorectal
    cancers
  • Part of Wnt-B-catenin
    pathway
183
Q

E- cadherin in tumour supressor genes

A

Loss of function
mutations can
contribute to loss of
contact-inhibition in
tumours and
metastasis

184
Q

All cancers display 8 fundamental changes in cell
physiology:

A
  1. Self-sufficiency in growth signals
  2. Insensitivity to growth-inhibitory signals
  3. Altered cellular metabolism
  4. Evasion of apoptosis
  5. Limitless replicative potential
  6. Sustained angiogenesis
  7. Ability to invade and metastasize
  8. Ability to invade the host immune system
185
Q

Warburg effect is when

A

Cancer cells take up high levels of glucose and
demonstrate increased conversion of glucose to lactate

  • Even in the presence of ample oxygen
  • Also called aerobic glycolysis
186
Q

Why do you suppose a cancer cell is relying on glycolysis alone for ATP production?

A

Provides rapidly diving tumour cell with metabolic
intermediates needed for synthesis of cellular
components

187
Q

T or F Cancer cells can evade senescence

A

T
- Likely due to loss of functions mutations in p53 and p16
- Allows cell to pass through G1/S checkpoint

188
Q

normal cells divide ….. times and then become senescent

A

60-70

189
Q

what are the componenets of the GI system

A

Alimentary canal
- esophagus
- stomach
- small intestine
- large intestine

accessory organs
- liver / galbladder
- pancreas

190
Q

what is the alimentary canal

A

tubular like structure that makes direct contact with food
- has a typical set of histologic layers that surrond the lumen

composed of :

oral cavity
pharynx
esophagus
stomach
small intestine
(duodenum , jejunum and ileum)
large intestine
( cecum, appendix, ascending , transverse, descending, rectum)

191
Q

what are the accessory organs

A

derived as outgrowths from alimentary canal

  • not part of the straight tube
  • function as glands and secrete substances into the canal

include
- salviary glands
- liver
- galbladder

192
Q

what is the main function of alimentary canal

A

propulsion
moving food along the tube

193
Q

what are the two secretions of the alimentary canal

A

hormonal
fluid or mucous

194
Q

what are the two types of digestion

A

chemical
- enzymes and acid that break down the bonds in food

mechanical
movements of the canal to mix food and break it apart and increase the SA : volume of food

195
Q

how is the absorbtion done in the alimentary canal

A

movement of lumen into blood stream

we ingest 1L of water a day, and 4-6 L of water into the canal

macro and micro nutrients

196
Q

what is the immune function of the alimentary canal

A
  • protection from ingested microbes that are harmful
  • aiding microbes that are useful
  • educating the immune system about weather something has been ingested is harmful or harmless
197
Q

what are the layers of the alimentary canal

A

mucosa - epithelial lining , laminal propria , muscularis mucosa

submucosa
muscularis
serosa

198
Q

where are neuroendocrine cells in the alimentary canal

A

interspersed among the epithelium and release signals in response to different nutrients or chemical conditions in the lumen

199
Q

columnar with microvilli help in what? cubodial or squamous?

A

absorbtion and secretion

protection from abrasion

200
Q

what is the purpose of goblet cells in the epithelial layer

A

mucous secretion

201
Q

what is the lamina propria a site of?

A
  • blood and lymphatic vessels
  • immune tissue
202
Q

what is the muscularis mucosa

A

used to alter the shape of the mucosa to optimize mixing and exposure of the epithelial cells to lumen contents

203
Q

the submucosa is

A

a loose connective tissue with larger blood vessels and lymphatics

  • larger glands
  • large lymphatic nodules
  • a plexus of neurons exist
204
Q

what is meissners plexus

A

tends to regulate secretions and convey sensory info about whats in the lumen

205
Q

muscularis layer is usually an …. and …. layer.

A

inner and outer

206
Q

the inner layer of the muscularis is

A

the circular layer
- smooth muscle fibres concentrically surround the lumen

when it contracts, it squeezes the lumen shut

207
Q

the outer layer of the muscularis is

A

the longitudinal layer
- smooth muscle fibres run along the length of the canal

208
Q

what is auerbachs or myenteric plexus

A
  • muscularis layer
  • regulates the movements of these muscular layers
    • found in between the two layers
209
Q

the adventitia layer of the alimentary canal

A

in the esophagus
- connective tissue that anchors the esophagus in the chest cavity

210
Q

the serosa layer of the alimentary canal

A

loose connective tissue that is covered by simple squamous mesothelium

  • mesothelium secretes fluid that collects in the abdominal (peritoneal) cavity
    • source of peritoneal fluid
    • serosa is continuous with what is known as the visceral peritoneum
211
Q

what is the peritoneal cavity

A

fluid filled gap between the wall of the abdomen and the organs that are contained within the abdomen

212
Q

where is visceral formed

A

by the serosa and the capsule of the layer

213
Q

what does the mesothelia secrete

A

fluid that collects in the abdominal (peritoneal) cavity

214
Q

the parietal is the ….. of the abdominal wall and is …… to inflammation and other …

A

inner lining
extremely sensitive
chemical irritants

215
Q

the only function of the esophagus is …..

A

propulsion of the food forward

216
Q

peritoneal cavity is to …

A

host the organs

217
Q

how long is the esophagus

A

25 cm long, located behind sternum

218
Q

what is the esophagus divided into

A

upper and lower sphincter

219
Q

what is the role of the upper sphincter

A

when it closes, it pushes the food from the pharynx to the esophagus

220
Q

what is the role of the lower sphincter

A

limits movement of the stomach acid into the esophagus

relaxes to receive swallowed food

221
Q

what type of cells does the esophagus have

A

stratified squamous, adventitia instead of serosa

222
Q

what is the purpose of the stomach muscular movements

A

mechanical digestion and propulsion into the small intestine

223
Q

what are the chemical digestion roles of the stomach

A

acid denatures proteins and kills ingested bacteria

secreted enzymes help to digest protein

tells when the stomach is full
(regulates food intake)

224
Q

in the stomach what kind of cells are there

A

low columnar cells

parietal cells
- secretes acid and intrinsic factors (B12 absorbtion)

  • other mucous secreting cells

muscularis
- oblique layer

225
Q

what is a pyloric sphincter

A

regulates the amount of acidic chyme that enders the duodenum

226
Q

the small intestine is the main

A

digestive organ

227
Q

what is the small intestine the site of

A
  • chemical digetion , absorbtion and secretion in the alimentary canal
  • large surface area
228
Q

what are the three seperate components of the small intestine

A

duodenum
- short C shaped tube that recieves chyme from the stomach and overlies the head of the pancreas

jejunum
- both the dudenum and jejunum have specialized immune tissue

ileum
- longest portion
- main function is reabsorbtion of bile, salts, water, micronutrients

229
Q

the small intestine has ……. , ….. and ….. meant to optimize surface area

A

highly folded epithlium
mucosa(villi)
submucosal layers(circular folds)

230
Q

small intestine consists of …. with many …. and is interspersed with ….. and cells that secrete chemical messages into the blood

A

columar epithelium

micorvilli

goblet cells

231
Q

messangers in the small intestine can help regulate

A

propulsion, overall metabolic function , secretions from the pancreas and liver

232
Q

the main function of the large intestine is

A

absorbtion of water , storage of stool , houses majority of microbes in the gut

  • not really involved in nutrient absorbtion
233
Q

what cells are the large intestine composed of

A

low columar cells with fewer microvilli

plenty of goblet cells

234
Q

what is unique about the muscular layer of the large intestine

A
  • continuous circular muscle layer
  • longitudinal muscle layer is separated into bands that do not completely surround the canal but always have circular layer
235
Q

why do we need the turns in the large intestine

A

slow down stool, accumulate stool , more mucous

236
Q

the accessory organs dont contact …….. directly. they all have ….. that convey their secretions to the lumen of the ….

A

ingested substances

secretions , duodenum

237
Q

what are the main roles of the liver

A
  • carb metabolism
  • protein synthesis
  • lipid metabolism
  • detox of molecules so that they can be secreted into bile and defecated
  • making hydrophobic molecules water soluble so that they can be eliminated by the kidney
  • storage of vitamins and minerals
  • synthesis of bile
  • endocrine secretion of IGF-1 (growth)
238
Q

what are the main functions of gallbladder and pancreas

A

galbladder
- storage and modification of bile (release into dudenum)

pancreas
- exocrine, secretes digestive enzymes that are crucial for carb , protein and lipid chemical digestion

endocrine
- secretes hormones that impact glucose , protein and lipid metabolism into the blood stream
(insulin, gluagon, lipids)

239
Q

increased bowel sounds (hyperactive) can be a indication of

A

diarrhea, gastoenteritis , IBS , laxitive use

early bowel obstruction

240
Q

what are some indications of decreased (hypoactive) bowel sounds

A

emergent conditions
- bowel obstruction , peritonitis , intestinal ischemia

241
Q

deep or visceral abdominal pain can come from

A

stretching, ischemia or chemical irritation of a component of the alimentary tract or accessory organ

242
Q

guarding of the abdomen is

A

voluntary contraction of the abdominal musculature due to abdominal discomfort

  • anxiety
  • can be serious but more often less
243
Q

what is rigidity of the abdomin

A

involentary contraction of the abdominal musculature , severe pain

bile (ruptured colecytitis) , infected material (rupture or ishemic intestinal wall), pancreatic secretions (pancreatitis) , gastric or duodenal contents (perforted peptic ulcer)

inflamed structure rubbing against the parietal peritoneum (appendicitis)

244
Q

abdominal pain in the centre is a sign of

A

visceral pain from the alimentary tract or accessory organs

245
Q

pain in the 6 side regions can be a sign of

A

irritation of the parietal peritoneum

non Gi organs

246
Q

hepatomegaly pathology

A

normal soft to abnormally hard or firm liver

increased size of liver

irregular edge - heppatocellular carcinoma

liver cirrhosis is
large liver with firm , non tender edge

Biomed (9 decks)

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