Test 2 Flashcards
(149 cards)
1
Q
Stem cell
A
A cell that retains the ability to divide and re-create itself while also having the ability to generate more progeny capable of specializing into a more differentiated cell type
2
Q
What does a stem cell divide into
A
Another stem cell and progeny that can differentiate
3
Q
Single cell asymmetry
A
A stem cell and a committed cell is produced at each division
4
Q
Population asymmetry
A
Some cells in a population are more prone to produce a differentiated cell
5
Q
Is population asymmetry symmetrical or not
A
Symmetrical
6
Q
Population asymmetry example
A
One stem cell divides into two stem cells OR two committed cells
7
Q
Adult stem cell lineage
A
A cell which goes through many rounds of cell division but eventually will turn into a differentiated cell
8
Q
Renewal
A
Continuous division of the stem cell
9
Q
Totipotent
A
A stem cell capable of producing all the cell types of a lineage
10
Q
Pluripotent
A
Capable of producing all the cells of the embryo. Cannot produce any extra embryonic membranes
11
Q
Multipotent
A
Function to generate cell types with restricted specificity for the tissues in which they reside. (Stuck in position. Divides to build up the tissue theyre in)
12
Q
Progenitor
A
Can only divide a few times before it differentiates. Works to amplify the number of cells. Will differentiate soon
13
Q
Precursor
A
Any ancestoral cell type to the differentiated cell. Lineage may not be known
14
Q
How are stem cells regulated between these different states in a coordinated way to meet patterning and morphogenic need of the embryo and mature tissue
A
Regulation is highly influenced by the microenvironment that surrounds a stem cell and is known as the stem cell niche
15
Q
Where is the stem cell niche found
A
All tissues possess a unique stem cell niche. Extracellular and intracellular changes regulate stem cell behavior
16
Q
Extracellular mechanisms
A
- Physical mechanisms
2. Chemical mechanisms
17
Q
Physical mechanisms
A
Structural adhesion factors within the ECM that support architecture of the niche. Differences in cell to cell and cell to matrix adhesions as well as cell density within the niche can alter the mechanical forces that influence cell behavior
18
Q
Chemical regulation
A
Secreted proteins from surrounding cells influence stem cell states and progenitor differentiation through endocrine, paracrine and juxtacrine mechanisms. If stem cells are too far from niche, the factors cant reach them and differentiation commences
19
Q
Interstitial fluid
A
Fluid not in the bloodstream
20
Q
Intracellular mechanisms
A
- Regulation by cytoplasmic determinants
- Transcriptional regulation
- Epigenetic regulation
21
Q
Regulation of cytoplasmic determinants
A
Partitioning which occurs at cytokenisis. As a stem cell divides, the factors determining cell fate are either partitioned to one daughter cell (asymmetric) or shared evenly between daughter cells (symmetric)
22
Q
Transcriptional regulation
A
Occurs through a network of transcription factors that keep a stem cell in its proliferative state , as well as promoting maturation of daughter cells towards a particular fate
23
Q
Epigenetic regulation
A
Occurs at the level of chromatin. Different patterns of chromatin accessibility influence gene expression related to stem cell behavior
24
Q
Blastocoel
A
Space in the middle filled with fluid to shift morula cells to one spot (ICM)
25
Inner cell mass (ICM) creates the _____
Epiblast or embryo proper
26
Trophoectoderm cells
Create the extraembryonic membrane
27
What happens if we remove cells from the ICM
We produce embryonic stem cells which retain pluripotency and can generate any cell in the body
28
Blastocyst
Special name for a mammalian blastula
29
How does the blastocyst form
After fertilization, cleavage creates the morula. Division continues until it hollows out to become the fluid filled blastocoel. Cells are pushed to one side to become the ICM which retains pluripotency for a while. Trophoblast will become extra embryonic structures
30
Symmetrical division parallel to apicobasal axis
Trophectoderm expands
31
Asymmetrical division perpendicular to apicobasal axis
ICM cell created - will not have the same proteins as the original cell and becomes a different cell type
32
Apicobasal axis
Outer side of the embryo to inner side
33
When does the asymmetrical localization along the apicobasal axis occur
At the morula stage
34
What specific factors are localized
1. ICM
| 2. Tropoectoderm
35
ICM localization
Results in the recruitment of E-cadherin to the basolateral membrane where outer cells contact underlying ICM cells
36
Trophoectoderm localization
PAR and aPKC families are localized to the outside cells, these factors are called partitioning proteins
37
Is E-cadherin important in influencing these cell lineages
Yes. E- Cadherin activates Hippo patheay but only in the ICM
38
Result of E-cadherin influencing cell lineages
1. Hippo activated in ICM and the maintenace of pluripotent ICM development through Oct4
2. PAR and aPKC inhibit Hippo leading to yap-taz-tead transcription complex which causes an upregulation of cdx2 and the trophoectoderm fate
39
Hippo on
Oct 4 turned on --> can act as stem cell
40
Hippo off
Cdx2 turned on --> stops cell from having stem cell ability
41
What does the hippo pathway prevent
Prevents cdx2 from being transcribed
42
What must adult stem cells do
1. Maintain a long term ability to divide
2. Be able to produce some differentiated daughter cells
3. Be housed in and controlled by its own stem cell niche which regulates stem cell renewal, survival, and differentiation
43
Where are neural stem cells found
1. Subgranular zone of the hippocampus (SGZ)
| 2. The ventricular-subventricular zone (V-SVZ)of the lateral ventricles
44
Germ line
The gametes are the product of the germ line that is separate from the somatic cell lineages
45
Meiosis
Chromosomal content is halved so the union of two gametes restores the full chromosomal complement of the new organism
46
How many cells does meiosis produce
4 haploid unidentical cells
47
Primary sex determination
Determination of the gonads
48
Secondary sex determination
Determination of the male and female phenotype by the hormones produced by the gonads
49
Bipotential gonad
Common precursor that male and female gonads diverge from
50
Gonads
Paired regions of the mesoderm that are adjacent to the kidneys
51
Male gonadal type
Testes
52
Female gonadal type
Ovary
53
Male germ cell location
Inside testes cords (medulla of testes)
54
Female germ cell location
Inside follicles of ovarian cortex
55
Remaining duct male
Wolffian
56
Remaining duct female
Mullerian
57
Male duct differentiation
Vas deferens, epididymis, seminal vesicle
58
Female duct differentiation
Oviduct, uterus, cervix, upper portion of the vagina
59
Male urogenital sinus
Prostate
60
Female urogenital sinus
Skenes glands
61
Male labioscrotal folds
Scrotum
62
Female labioscrotal folds
Labia majora
63
Male genital tubercle
Penis
64
Female genital tubercle
Clitoris
65
Female karyotype
XX
66
Male karyotype
XY
67
What is it in the Y chromosome that makes a male a male
Testis-determining factor (SRY gene) which organizes the bipotential gonad into testes
68
SRY active at the proper time
Male gonads, inhibits ovary formation
69
SRY gene is not present or fails to act at the appropriate time
Ovary forming genes will function. Female gonads
70
When do gonadal rudiments appear
Week 4 and remain sexually indifferent until week 7
71
6 weeks wolffian duct
Indifferent gonad shows expanded epithelium. Mesoderm continues to proliferate
72
8 week testes development
Developing sertoli cells surround incoming germ cells and organize themselves into testes cord near kidney. Anti mullerian hormone secreted. Seminferous tublues form
73
16 weeks male
Wolffian duct differentiates to become epididymus and vas deferns. Efferent ducts are the remodeled tubules of the developing kidney
74
8 weeks ovarian development
Each germ cell gets enveloped by a cluster of sex cord epithelial cells. Germ cells become eggs and surrounding cortical epithelial cells will differentiate into granulosa cells
75
20 weeks female
Remaining mesanchyme cells differentiate into thecal cells. Thecal and granulosa cells form follicles that envelope germ cells and secrete steroid hormones. Ovary does not connect to the wolffian duct
76
Cells that surround oocyte
Granulosa closest
| Theca on outer layer
77
Genes expressed in bipotential gonad
Wt1, Lhx9, GATA4, Sf1
78
Where is Wnt4 expressed
In the bipotential gonad and ovaries, not the testes
79
____ acts with Wnt4 to produce _____
Rspo1, B-catenin
80
What is beta catenin important for
Activating further ovarian development and blocking synthesis of Sox9 (a testes determining factor)
81
What transcription factors for development does B-catenin activate
FoxI2 and follistatin
82
What is follistatin responsible for
Organizing epithelium in granulosa cells
83
Evidence that the SRY gene is located on the Y and determines sex
Inserting SRY into genome of a normal XX zygote will make the XX mouse form testes
84
What gene goes the SRY gene activate to induce testes formation
Sox9
85
Meiosis vs mitosis
1. Meiosis is two cell divisions without an intervening period of DNA replication
2. Homologous chromosomes pair together and recombine genetic material
86
How do homologous chromosomes find eachother
Based on size and sequence
87
Leptotene
Search
88
Zygotene
Association of homologous chromosomes -synapse
89
Pachytene
Homologous chromosomes completely aligned
90
Diplotene
Recombination
91
Spermatogenesis
The development pathway from germ cell to mature sperm cell
92
Spermatogonia
Sperm stem cell
93
Spermiogenesis
Physical maturation of a sperm cell
94
Step 1 spermatogenesis
Spermatogonia divide -proliferative phase
95
Step 2 spermatogenesis
Meiotic phase - meiosis occurs (completes before spermiogenesis)
96
Step 3 spermatogenesis
Spermiogenesis - sperm is shaped and matured
97
Spermatogonia division
One stem cell, one cell that will go into meiosis and spermatogenesis
98
Layers of cells in the seminiferous tubule
- Stem cells outside
- 1 st meiotic division
- 2nd meitoic division
- Meiosis complete
- Mature sperm in center
99
Low levels of GDNF favor_____
Differentiation of spermatogonium
100
Oogonia
Stem cell that divides
101
Primary oocyte
Undergoes one round of meiosis and is stuck in the diplotein stage until puberty
102
Secondary oocyte
Released by the ovary in the stage of metaphase II. Meiosis is completed upon fertilization
103
Meiosis in oocyte
oogonia --> primary oocyte (meiosis round 1, stops in diplotein phase) --> secondary oocyte (stops at metaphase 2 until fertilization) --> meiosis is complete
104
What does an oogonia split into
Primary oocyte and stem cell to replace itself
105
Why do older women have a higher chance of giving birth to a fetus with an extra chromosome
Break down of cohesion proteins needed during meiosis which causes aneuploidy
106
How long is meiosis
16 hours to assemble meiosis spindle, 4 hours in mice
107
Why are more downs syndrome babies born to younger women if older women have a higher chance of having them
Younger women have more babies in general
108
Four major events of fertilization
1. Contact and recognition between sperm and egg
2. Regulation of sperm entry into the egg
3. Fusion of genetic material of the sperm and egg
4. Activation of egg metabolism to start development
109
What is the sperm tail made of
Centrioles, made of microtubules
110
What powers the tail of the sperm
Mitochondria
111
What does the golgi form in the sperm
Acrosomal vesicle
112
What happens to the remaining cytoplasm in the sperm
It is expelled to get rid of extra weight
113
What enters the egg from the sperm during fertilization
The nucelus and centriole
114
Structure of sea urchin egg
Plasma membrane (inner), Vitelline envelope (middle), Jelly coat (outer)
115
How is polyspermy prevented in the sea urchin egg
The vitelline envelope condenses to prevent more than one sperm from fertilizing the egg
116
Germinal vesicle
Name given to the large diploid nucelus of the primary oocyte
117
When does the sperm enter the egg in most mammals
Second metaphase
118
When does the sperm enter the egg in sea urchins
Meiosis complete
119
Structure of mammalian eggs
Plasma membrane (inner), zona pelicuida (middle), cumulus (outer)
120
What is the vitilline analogous to in the mammal
Zona pelucida
121
What is the jelly layer analogous to in the mammal
Cumulus
122
Steps of fertilization in sea urchin
1. Sperm contacts jelly layer
2. Acrosome reaction
3. Digestion of jelly layer
4. Binding to vitelling envelope
5. Fusion of acrosomal process membrane and egg membrane
123
Steps of fertilization in mammals
1. Sperm activated by female reproductive tract
2. Sperm binds to zona pelucida
3. Acrosome reaction
4. Sperm lyses hole in zona
5. Sperm and egg membrane fuse
124
How does sperm travel through the female
Chemotaxis, sperm goes towards higher concentration of chemotaxis faster
125
Chemotaxis pathway in sea urchin
Resact from egg binds to RGC --> GTP --> cGMP--> Ca2+ --> sperm swim towards egg
126
Protein for sperm egg recognition
Bindin
127
Why cant different species have offspring
Bindin is species specific
128
How do sperm know where to bind to the egg
Sperm only bind where bindin receptors are on egg
129
Dispermic sea urchin process
1. Fusion of three haploid nuclei (18 chromosomes each)
2. 54 chromosomes randomly assort on the four spindles
3. Duplicated chromosomes pulled to four poles during anaphase I
4. Four cells contain different numbers and types of chromosomes
5. Early death of embryo
130
Potential of egg membrane before sperm
-70 mV
131
Slow block to polyspermy
1. Sperm surround egg 10 seconds after addition
2. 25 and 35 seconds after, fertilization envelope is formed around the egg starting at point of sperm entry
3. Fertilization envelope is complete and excess sperm are removed
132
Fast block to polyspermy
-70 mV to +120 mV
133
Formation of sea urchin fertilization envelope
Corticle granules fuse with plasma membrane, H20 breaks connection
134
Where are calcium ions released from
The ER
135
Where is the bindin protein on the sperm
In the acrosomal process
136
Mucopolysaccharides
Produce the osmotic gradient for the fertilization envelope
137
Peroxidase enzyme
Crosslinking tyrosine residues. Hardens envelope
138
Hyalin
Coating around the egg
139
What surrounds the cortical granules in sea urchin eggs
Endoplasmic reticulum
140
Formation of fertilization envelope pathway (mechanism of egg activation)
PIP2 --> IP3 --> Ca released from ER --> cortical granule exocytosis (fertilization envelope develops)
141
What else does PIP2 activate
DAG
142
G protein involvement in Ca entry into sea urchin eggs
Sperm contact and fusion --> G protein activation --> Src activation --> PLCy activation --> PIP2 --> IP3/DAG --> Ca release --> cortical granule exocytosis (slow block) OR inactivation of MAP kinase (reinitiation of cell cycle)
143
Sperm capacitation
Removal of cholesterol by albumin --> influx of ca and bicarbonate --> promote AC activity --> make cAMP from AMP --> protein kinase A (inhibit PTP) --> PTK --> phosphorylate capacitation proteins
144
What must a sperm go through in order to fertilize
Capacitation
145
Why doesn't the first sperm to reach the egg fertilize it
It probably did not go through capacitation. Capacitation is a long process
146
Where does the acrosomal reaction occur in mammals
Cumulus
147
What is the zona pellucida made of
Four glycoproteins: ZP1, ZP2, ZP3, ZP4
148
Which glycoprotein blocks polyspermy in mammals
ZP2
149
How does the nuclei of the egg and sperm migrate to eachother
Migrate following microtubules
