Exam 4 Flashcards
What kind of cells are involved in sexual reproduction?
diploid & haploid cells
How does a hydra reproduce?
budding
Are all offspring genetically identical to the parent?
yes
Is there any genetic variability in a changing environment? If so, what?
yes, mutations
If a hydra gets stressed in certain ways, what happens?
it goes into sexual reproduction
Does a hydra live a longer life or a shorter one when it goes into sexual reproduction?
shorter life
How are sperm and egg gametes produced?
by meiosis
Parent cells are ________, while germ cells are ________.
diploid; haploid
What does fertilization result in?
diploid embryo
Why is there an advantage in sexual reproduction?
because of the separation and recombination or genes
How many gametes are the parental pair split into?
4 gametes
What is the function of gametes?
propagate genetic information to next generation
What is the function of somatic cells?
form body of the organism but they leave no progeny
Germ cells (gametes) are responsible for?
genetic variability
What are the three rounds involved in meiosis?
one round of DNA replication followed by two rounds of nuclear division
When do duplicated homologous chromosomes pair?
meiotic prophase
What does “crossing over” occur between?
the duplicated maternal and paternal chromosomes in each bivalent
What ensures the proper segregation of homologs?
chromosome pairing and crossing-over
What does the second meiotic division produce?
haploid daughter nuclei
What is “crossing-over”?
DNA exchange from chromosome to chromosome
Fertilization constitutes a…
complete diploid genome
Does DNA replication occur in meiosis 1 & 2?
no, it only occurs in meiosis 1
What is the difference, in stages, of mitosis and meiosis?
mitosis has replication followed by one round of division, meiosis has replication followed by two rounds of division
Meiosis generates…
four nonidentical haploid nuclei
Mitosis produces…
two identical diploid nuclei
What is a bivalent?
duplicated maternal and paternal chromosome pair
When does “crossing-over” occur?
during meiosis 1
What is exchanged between bivalent chromosomes during crossing-over?
pieces of chromosomes
Where and what do crossing-over points form?
form a chiasmata between non-sister chromatids in each bivalent
What occurs in meiosis 2?
chromatid separation that results in haploid gametes, also realignment and formation of new kinetochores
What is the result of meiosis 1?
primary oocyte and polar body 1 (diploid)
What is the result of meiosis 2?
secondary oocyte and polar body 2 (haploid)
What two aspects of genetic reassortment generate new chromosome combinations?
crossing-over during meiosis 1 and independent assortment of maternal/paternal chromosomes during meiosis 2
What is one example of infidelity in chromosome segregation?
nondisjunction
What is nondisjunction?
result of failure to separate duplicated chromosomes during meiosis
What is an example of nondisjunction?
trisomy 21
What is the result of nondisjunction?
aneuploid gametes
How are multicellular organisms built?
organized collections of cells
What gives a plant cell wall its tensile strength?
cellulose microfibrils
What do animal connective tissues consist largely of?
extracellular matrix
What provides tensile strength in animal connective tissues?
collagen
Do cells organize the collagen they secrete?
yes
What proteins couple the matrix outside of a cell to the cytoskeleton inside?
integrins
What fills spaces and resist compression?
gels of polysaccharides and proteins
What polysaccharides do cell walls contain?
cellulose and pectin
How is cellulose microfibril formed?
from a bundle of cellulose molecules
What helps direct the deposition of cellulose in the plant cell wall?
microtubules
What is cellulose synthetase?
transmembrane enzyme protein complex
What does cellulose synthetase do?
- assembles glucose into cellulose polymers to form microfibrils
- connected to linear arrays of sub membrane microtubules by connector proteins
How is the plant plasma membrane extended?
as glucose is supplied it is added to the membrane
What matrix protein provide strength and deformability?
collagen
Is collagen soluble?
no, it is very insoluble
How is collagen assembled?
- procollagen precursor protein is synthesized and secreted by the cell
- protease cleavage outside of cells release collagen molecule
- collagen molecules self-assemble to form collagen fibrils
Can collagen be formed by pro collagen?
no
Does the original pro collagen polymerize past the triplet?
no
What can incorrect collagen assembly cause?
skin to be hyperextensible
Fibronectin proteins do what?
bind collagen fibrils outside cells and also bind to integral proteins on plasma membranes
How do integrins transmit tension across the plasma membrane?
by anchoring to actin filaments in the cell cytoplasm
Some integrins bind to _______, but most bind to ________.
intermediate filaments; actin filaments
What happens if there is a fibronectin defect?
cells won’t attach and will migrate for forever waiting for the fibronectin signal
Epithelial sheets are polarized and rest on what?
the basal lamina
What are the two surfaces of epithelial cells?
apical and basal
Which of the two surface of an epithelial cell is free?
apical surface
What is the basal lamina composed of?
collagen, elastin, fibronectin, etc.
What polarized cell types make up the epithelial lining of the intestine?
absorptive cells and goblet cells
Describe absorptive cells.
take up nutrients
contain microvilli which increases surface area of plasma membrane for transport of molecules
Describe goblet cells.
secrete mucus
contain secretory vesicles loaded with mucus
What kind of tissue type is the basal lamina?
connective tissue
What makes the epithelium leak proof and separates its apical and basolateral surfaces?
tight junctions
Tight junctions in the epithelium only allow for what?
the selective transport of desirable molecules
Epithelial cell tight junctions allow what to serve as barriers to molecular diffusion?
cell sheets
What are claudin and occludin proteins?
plasma membrane proteins that span the membranes of interacting cells and seal tight junctions
Where are claudins and occuldins synthesized?
rough ER
Are claudins and occludins glycoproteins?
no because they form really tight junctions and are very exclusionary
Cytoskeleton-linked junctions bind epithelial cells to what?
robustly to one another and to the basal lamina
Describe tight junctions.
seals neighboring cells together in epithelial sheet to prevent leakage of molecules between them and helps polarize cells
Describe adherens junctions.
joins actin bundle in one cell to a similar bundle in a neighboring cell
Describe desmosomes.
joins intermediate filaments in one cell to those in a neighbor
Describe gap junctions.
form channels that allow small, intracellular, water-soluble molecules to pass from cell to cell
Describe hemidesmosomes.
anchors intermediate filaments in a cell to the basal lamina
What is the result of adherens junctions?
have actin filaments that go across cells like a band
How do hemidesmosomes bind?
through receptors
What is formed around epithelial cells in the small intestines?
adhesion belts
How are contractile bundles of actin filaments linked to adjacent cells?
by transmembrane cadherins
Where do contractile bundles of actin filaments run?
along cytoplasmic surface of plasma membrane near cell apex
What are signals for cell cell contact sites?
cadherins
What kind of proteins are cadherin proteins?
plasma membrane proteins
What happens when a cadherin mutates?
lowers the chances of forming bundles drastically
What do cadherin proteins attach to?
actin or keratin intermediate filaments via linker proteins
Cadherins concentrate at points of cell cell attachment to form…
adherens junctions
How do cadherins recruit linker proteins that dictate actin formation?
through interaction
How do epithelial sheets form epithelial tubes?
they bend
What are examples of epithelial sheets forming epithelial tubes?
neural tube formation during development
formation of eye cup and pinched off lens vesicle
Desmosomes link what of one epithelial cell to those of another?
keratin intermediate filaments
What anchors keratin filaments in an epithelial cell to the basal lamina?
hemidesmosomes
Is linkage in hemidesmosomes mediate by integrin or cadherin proteins?
integrin
What binds keratin filaments to integrin proteins?
plaques of linker proteins
Where do plaques form in hemidesmosomes?
at the touch points
Do hemidesmosomes interact with extracellular matrix?
yes
What do gap junctions allow to pass from cell to cell?
inorganic and small molecules
What do gap junctions provide for neighboring cells?
with a direct channel of intercystolic communication
interacting plasma membranes are penetrated by what complexes that make up gap junctions?
connexon protein complexes
What dictates the size of a gap junction?
by formation and structure of the portals
Connexon form portals through what?
interactions
What regulates the permeability of gap junctions?
extracellular signals
Treatment of the retina with what decreases permeability of gap junctions?
dopamine
Can many cell types go into making different types of tissues?
yes
What is an example of many cell types going into tissues?
the retina
Are different tissues renewed at different rates?
yes
What generates a continuous supply of terminally differentiated cells?
stem cells and proliferating precursor cells
What maintains stem cell populations?
specific signals
What can stem cells be used for?
repair lost of damaged tissues
What type of stem cells provide a convenient source of human embryonic cells?
induced pluripotent stem cells
What can mouse and human pluripotent stems cells form?
organdies in a culture
What is the epidermis?
epithelial cells
What is the dermis?
connective tissue, loose layer, and dense layer
What is the hypodermis?
fatty connective tissue
What two layers of skin are casularized and innervated?
dermis and hypodermis
What is keratins intermediate filament?
keratocytes
What generates the collagen matrix?
fibroblasts
What happens when a stem cell divides?
the daughter cells can either remain a stem cell or become terminally differentiated into a defined function
Precursor cells slide upward and terminally differentiate into what cells in the process of cell replacement in the epithelial lining of the intestine?
secretory and absorptive cells
Where are secretory and absorptive cells shed?
from the tip of the villus
Are microvilli and villi the same thing?
no
Collagen is a major protein of what?
the basal lamina
Cells attach to what by integrin in cell replacement in the epithelial lining of the intestine.
fibronectin
What kind of epithelium is renewed from stem cells in the basal layer?
stratified
Cells undergo programmed cell death leaving what packed with keratin intermediate filaments that are ultimately shed?
flattened scales
Does blood contain many circulating cell types?
yes
Blood is derived from what?
a single type of stem cell in the bone marrow
Hemopoietic stem cells divide to do what?
generate more stem cells and various types of precursor cells
Precursor cells divide and differentiate into what found in the circulation?
mature blood cell types
What does the Wnt signal pathway do in the intestinal crypt?
maintains proliferation of the stem cells and precursor cells
What happens in the absence of Wnt?
cells stop mitosis and proliferation and differentiate to final cell types
What do you have to stop in order to go into differentiation in the intestinal crypt?
mitosis
When there is no Wnt what happens?
they go down the pathways of their differentiations
Wnt signaling pathways controls the degradation of what?
beta catenin
What does beta catenin control?
transcription
What protein keeps the Wnt signaling pathway inactive in the absence of Wnt?
APC
When Wnt is active, APC is inactive which releases what?
active beta catenin
Mutations in APC initiate what?
tumors
Does beta catenin ever reach a threshold?
no
Mouse Es are harvested from the inner cell mass of the embryo during what stage of development in the culture?
blastocyst stage
Treatment with what of the Mouse ES induced differentiation into specific cell types?
different signaling
What are pluripotent stem cells?
cells that have the ability to undergo self renewal and give rise to all cells of the tissues of the body
Can pluripotent cells be deprogrammed and made into embryonic stem cells?
yes
Can embryonic stem cells be differentiated into any cell of the body?
yes
What happens to human pluripotent cells in a culture?
proliferate, differentiate, and self assemble into tissues
What is the eye cup and example of?
3D, multilayered, retina with similar organization to normal eye during development
What do cancer cells do?
proliferate excessively and migrate inappropriately
Do cancer cells exhibit contact inhibition?
no
How does cancer develop?
by accumulation of somatic mutations
What are the two main classes of genes that are critical for cancer?
oncogenes and tumor suppressor genes
Do cancer critical mutations cluster in one or a few fundamental pathways?
a few
Oncogenes are what in the genes which can cause cancer?
single mutations
What do tumor suppressors do?
suppress cell growth
Are cadherins distributed throughout the cells?
yes
What are cadherins important for?
the formation of cell junctions
What are cell cell contact issues due to?
cadherins
What is Wnt?
a ligand for GPCR receptor
Wnt controls beta catenin levels through…
APC proteolysis
Cadherins form cell cell adhesions and bind beta catenin which controls what?
free beta catenin levels
What are the multiple steps in processing encompassing of metastasis?
- infiltration of tumor cells into the adjacent tissue (intravascular system)
- migration of cancer cells into vessels known as intravasation
- survival into circulatory system
- extravasation, entry into receptive organs
- proliferation to competent organs
Where can cancer cell migrate?
through the basal lamina, blood, or lymphatic vessels
What do cancer cells secrete?
matrix metalloproteinases (MMPs) invlved in digesting connective tissues
What has a lot to do with the specificity of targeted secondary sites?
integrin expression and mutations
What are the common sites of lung cancer metastases?
bones, liver, brain, lymph nodes, adrenal glands
What is colon cancer a function of?
aging
What are the factors that can contribute to genetic instability?
- defects in DNA replication
- defects in DNA repair
- defects in cell cycle checkpoints
- mistakes in mitosis
- abnormal chromsome numbers
What is genetic instability the result of?
failed cell cycled regulatory checkpoints and mitosis
Breast cancer karyotypes show what?
multiple chromosome translocations
What happens to cancer cells over time due to mutations?
become more aggressive and less responsive
How do tumors evolve?
repeated rounds o mutation, proliferation, and natural selection
What becomes a dominant clone in the tumor?
daughter cell progeny
Mutations in what are dominant?
proto-oncogenes
Mutations in single gene copy induces what?
cell proliferation and cancer
Are mutations in tumor suppressor genes dominant or recessive?
recessive
What in a single copy of the proto-oncogene can drive a cell towards cancer?
gain of function mutation
In a tumor suppressor gene both copies of the gene must what in order to drive the cell towards cancer?
lose function
What converts proto-oncogenes to oncogenes?
gain of function mutations
Both copies of a tumor suppressor gene must be lost in order to…
eliminate tumor suppressor function
What are the key regulatory pathways perturbed in most human cancers?
- alterations in cell proliferation
- alterations in DNA damage response
- alterations in cell growth
- alterations in cell survival
Can years pass before tumors become noticeable>
yes
Typical treat tumor doubles cell number how often?
about every 100 days
