Exam 1 Flashcards
(121 cards)
1
Q
Embryology
A
Study of the embryo
2
Q
When does primordial germ cells first appear?
A
24 days
3
Q
List the Migration route of the primordial germ cell into the gonads
A
1) Yolk Sac
2) Hindgut Epithelium
3) Dorsal Mesentery
4) Into developing gonads
4
Q
Tetraoma
A
Growths from misdirected migrating primordial germ cells
5
Q
What are tetraomas made of?
A
Highly misdirected differentiated tissues
6
Q
Meiosis Prophase 1: Leptotene
A
- Chromosomes are thread like
- Each chromosome consists of two chromatids connected via cohesin
- Chromosomes begin to coil
7
Q
Meiosis Prophase 1: Zygotene
A
- Homologous chromosomes pair (Synapsis)
- Synaptonemal complex forms
8
Q
Meiosis Prophase 1: Pachytene
A
- Maximum coiling
- Tetrads
- Crossing over begins and occurs at hot spots
9
Q
Meiosis Prophase 1: Diplotene
A
- Crossing over continues
- Chiasmata are well defined
10
Q
Meiosis Prophase 1: Diakinesis
A
- Crossing- over is complete
- Terminalization
- Spindle apparatus is in place
- Nuclear membrane is disrupted
11
Q
Meiosis: Metaphase 1
A
- Tetrads line up along equatorial plate
- Centromeres do not divide
12
Q
Meiosis: Anaphase 1
A
- Homologous chromosomes consisting of two chromatids move to opposite poles
- Chromatids are not genetically identical b/c of crossing over
- Daughter cells will be haploid
13
Q
Meiosis: Telophase 1
A
- Cytokinesis occurs
- Nuclear membranous reform and spindle apparatus disassembles
- Chromosomes may uncoil to varying degrees
14
Q
Meiosis: Prophase II
A
- Chromosomes again condense
- Nuclear membrane disappear
- Each chromosome consists of two chromatids
- Each daughter cell has one complete set of chromosomes (haploid)
15
Q
Meiosis: Metaphase II
A
-Chromosomes line up on equatorial plate
16
Q
Meiosis: Anaphase II
A
- Centromeres divide
- Chromosomes move to opposite poles
- Each chromosome consists of a single chromatid
17
Q
Meiosis: Telophase II
A
- Chromosomes uncoil
- Cytokinesis is complete
- Nuclear membranes reform
- End result is four genetically unique haploid daughter cells
18
Q
Nondisjunction
A
Failure of homologous chromosomes or sister chromatids to separate properly
19
Q
Aneuploidy
A
Abnormal # of chromosomes
Examples: Monosomy and Trisomy
20
Q
Euploidy
A
Changes in number of complete sets of chromosomes
Examples: Monoploidy (Haploidy), Diploidy, Polyploidy
21
Q
oocyte at birth
A
2 million
22
Q
of oocyte shortly after birth
A
400,000
23
Q
of oocyte prior to puberty
A
40,000
24
Q
Describe the follicle and oocyte: Before Birth
A
- Primordial Follicle
- Primary oocyte (2n4c)
25
Describe the follicle and oocyte: After Birth
```
Primary Follicle
Primary Oocyte (2n4c)
```
26
Describe the follicle and oocyte: After Puberty
Secondary Follicle
| Primary Oocyte - arrested @ metaphase I
27
Describe the oocyte associated with a Tertiary Follicle
- Secondary Oocyte + Polar Body I
| - 1n2c
28
What come after the tertiary follicle
Secondary oocyte + Polar body I
| -1n2c
29
Fertilized Ovum
- Occurs after the ovulated ovum
- Fertilized ovum + Polar body II
- 1n1c + sperm
30
Describe the structure of the mature follicle
1) Theca Externa- Produces Angiogensis factor
2) Theca International - with LH receptors
- secretes testosterone
3) Membrane granulosa
4) Mural granulosa cells
- Develops FSH receptors
- Synthesizes aromatase in response to FSH
- Aromatase converts testosterone into 17B-estradiol
- Estrogen stimulates formation of LH receptors on granulosa cells
5) Antrum
6) Cumulus (oophorus) cells
- Facilitates the release of ovum @ ovulation
- Doesn’t express receptors
7) Zona Pellucida
- Involved in fertilization
8) Oocyte
31
How is aromatase synthesized and what does it do?
- FSH binds to FSH receptors on mural granulosa cells
- Stimulates the synthesis of aromatase
- Aromatase converts testosterone into 17-B Estradiol
32
Where are LH receptors located?
Granulosa cells of the Theca Interna
33
What is the action of LH?
LH stimulates the release of Testosterone
34
What does estrogen stimulate when interacting with granulosa cells of the Theca interna?
Cause the stimulation of LH receptors
35
When there is increased levels of cAMP in an embryonic oocyte what occurs?
cAMP inactivated maturation promoting factor (MPF) which causes meiosis arrest
36
LH causes closure of what type of junctions of cumulus cells
Gap Junctions
37
Describe the fate of the follicle after ovulation occurs
1) Oocyte is released (Ruptured Follicle)
2) Corpus Luteum forms
3) Corpus Albicans forms
38
Describe the events that propel the egg down the uterine tube
1) Fimbriae of uterine tube moves closer to ovary and sweeps across surface
- Increase in ciliation of tube epithelial cells
- Increase in activity of tubal smooth muscle cells
2) Capture of egg and surrounding follicle cells by uterine tube
3) Transport of egg occurs mostly via contractions of tubal smooth muscle
39
Describe the time it take for the egg to get to the Uterus
1) Slow transport in ampulla last about 72hrs
2) Rapid Transport through isthmus lasts about 8hrs: requires progesterone
3) Uterine arrival time is in about 3-4 days
40
What does a surge in LH cause?
Release of oocyte and corona radiata
41
Define Spermiogensis
The differentiation and maturation of the spermatids into motile spermatozoa (Final part of spermatogenesis)
42
Define Spermatogenesis
Complete process of the production of functional male gametes
43
List the stages of spermatogenesis
1) Primordial Germ Cells (2N)
2) Spermatogonia (2N
- Type A: Stem Cells
- Type B ~ leave mitotic cycle and enter meiosis cycle under influence of retinoic acid
3) Primary Spermatocytes (2N)
- First maturation division (meiosis I)
4) Secondary Spermatocytes (N) x 2
- Second maturation division (meiosis II)
5) Spermatids (N) x 4
- immature haploid gametes
6) Spermatozoa via spermiogensis
- haploid gametes
44
Location of Leydig cells
Testes
45
Function of Leydig cells
Produce Testosterone
46
Describe major meiosis events that occurs at each stage of spermatogenesis
1) First meiotic division occurs in primary Spermatocytes
| 2) Second meiotic division occurs on secondary Spermatocytes
47
List four major stages of spermiogenesis
1) Golgi Phase
2) Cap Phase
3) Acrosomal Phase
4) Maturation Phase
48
Describe the major events that occur during the four stages of spermiogenesis
1) Golgi Phase
- Proacromal vesicles
- Acromal vesicles
2) Cap Phase
- mature acromosome forms a cap over nucleus
3) Acrosomal Phase
- Rotation of sperm so that Acrosomal pole faces wall of seminiferous tubule cytoplasm displaced toward tail
4) Maturation Phase
- Completion of flagellum
- completion of nuclear condensation
49
Where are steroli cells (sustentacular cells) located
Seminiferous Tubules of the testes
50
Describe the Functions of Sertoli Cells
1) Physical Spport and maintenance
2) Maintain and coordinate spermatogenesis
3) Secrete estrogen, inhibin and anti-mullerian factor
4) Maintain blood-testis barrier
5) Secrete tubular fluid
6) Phagocytose residual bodies of sperm cells
51
Describe the relation of steroli cells to the blood testis barrier
They form an immunological barrier between the forming sperm cells and the rest of the body and spermatogonia
52
Role of testosterone in the blood testis barrier
Stimulates the formation of a new blood testis barrier closer to the basal lamina
53
Describe the action of LH on interstitial cells and Sertoli cells with regard to sperm cell production
1)LH is secreted by a anterior pituitary in response to GnRH from hypothalamus
2) LH binds to receptors on interstitial cells of leydig
- cause leydig cells to synthesize testosterone from cholesterol
3) Testosterone is carried via the blood to Sertoli cells and to secondary tissues
4) FSH stimulates sertoli cells to convert testosterone to estrogen and stimulate leydig cell stimulatory factor
5) Sertoli cells produce androgen-binding protein
- Binds testosterone and Carries it to fluid compartment of seminiferous vesicles
6)Sertoli cells produce inhibin
54
List the mechanisms that propel the immobile sperm through male tract
1) Passive transport via testicular fluid
2) Smooth muscle contractions
3) Cilia form seminiferous tubules
- Occurring through rate testis, efferent ductules, head of epididymis
55
Where does sperm maturation occur, and how long does it require
1) Maturation occurs in Epididymis
| 2) up to two weeks
56
What contributions are made to semen by the seminal vesicles and the prostate gland
Seminal vesicles: Fructose and Prostaglandins
| Prostate: Citric Acid, Zn, Mg, Phosphatase
57
Optimal pH for stem motility
6.0-6.5 (Found in. The Cervix)
58
How does the optimal pH compare to the upper Vagina
1) Upper Virginia has a pH of 4.3 and the optimal pH of the sperm is 6.0-6.5
2) Seminal Fluid buffers the acidity and increases pH to 7.2
59
What mechanisms move sperm up the oviduct
1) Swimming movements
| 2) Peristaltic contractions
60
Where does fertilization usually occur
Ampulla
61
Describe Sperms Rapid Transport through the cervical canal
1) Some spermatozoa reach uterine tubes within 15-20min after ejaculation
2) Relies mostly on muscular movements of female tract
3) Sperm not as capable of fertilizing egg
62
Describe sperm slow transport
1) Involves swimming through cervical mucous
2) 2-3mm per hr
3) Storage in cervical crypts
4) may not reach oviducts for 2-4 days
63
When does ovulation occur in the ovarian cycle and what role do FSH and LH play in ovulation
1) Ovulation occurs on day 14 of the cycle
2) FSH cause development of the Graffian Follicle
3) LH surge causes development of corpus luteum
64
What is the source of estradiol during the follicular phase and what is it responsible for?
1) Granulosa lutein cells secrete increased amounts of progesterone + estrogen
2) Necessary to maintain the implantation of the fertilized oocyte
65
What components of the Graafian follicle form the corpus luteum
Residual Theca and Granulosa Cells
66
What is the fate of the corpus luteum in absence of fertilization
1) Corpus luteum regresses due to decrease in FSH secretion via inhibin
2) Levels of progesterone and estradiol decreases which results in new menstrual phase
67
Function of Inhibin
1) Released by granulosa cells
2) Inhibits secretion of gonadotropins (esp. FSH)
- Results in regression of corpus luteum
* *Replacement of granulosa lutein cells with collagenous scar tissue results in the formation fo the corpus albicans
68
What is the function of ZP3 in Acrosomal reaction
1) Zona Pellucida (ZP) mediates attachment of sperm to ZP
- Glycoproteins cause an increased influx of Ca2+ through sperm plasma membrane
- Influx Na+ and Efflux H+ increase the pH
69
Where is acrosin (Zona Lysin) initially found and what’s its function in fertilization
1) Acrosin is from the acrosome and is linked to the plasma membrane when acrosome fuses with membrane
2) Has serine protease activity and involved in penetration of ZP
- Allows spermatozoa through ZP
70
Fast Block
- Rapid depolarization of egg plasmalemma
| - Temporarily prevents polyspermy for the egg to set up slow block
71
Slow Block
Swelling that increases width of periviteline space cause by carbohydrate release from cortical granules
72
Describe the formation of the fertilization membrane from the Vitelline membrane and cortical granules
1) Sperm penetrates the jelly coat
2) Lytic enzymes of the acrosomal filaments allows penetration of vitelline and plasma membrane
3) Hyaline cytoplasm flows toward sperm creating fertilization cone
4) Cortical granules with dark bodies move closer and fuse with vitelline membrane when dark bodies are released
5) Space between vitelline membrane and plasmalemme increase due to increased H20 in space
6) Dark bodies form continuous layer fused with the undersurface of the vitelline membrane
73
What is the role of phospholipase C zeta in metabolic activation of egg following fertilization
-Phospholipase C Zeta is released by sperm and initiates release of Ca2+ within egg cytoplasm
74
Distinguish between pronuclei and Zygote
1) Proneucleus: Nuclear material of spermatozoa or oocyte after oocyte has been penetrated
2) Male and female pronuclei fused and share common membrane
75
Dating Pregnancy
1) Fertilization Age: Dates of embryo from time of fertilization
2) Menstrual Age: Dates age of embryo from start of mother’s last menstrual period
- 2 weeks greater than fertilization age
76
Describe events that occur following fertilization and prior to implantation as the embryo travels down the oviduct
1) Zygote becomes metabolically active
2) Zygote begins to undergo cleavage (mitotic activity)
3) Embryo is transported down uterine tube to uterus
4) Journey takes several days
5) Embryo loses ZP prior to implantation
6) Implantation
77
Describe the process of cleavage in the mammalian embryo, including the formation of the blastocyst
1) Zygote undergoes mitotic division to form an 8 cell embryp
2) Cell division continues and compaction occurs
- Outer blastomere adhere via gap junctions facilitated by E-cadherins and Ca2+-dependent CAMs
- Out blastomere lose their individual identity
3) Water is transported into the ball of cells
- Occurs 4 days after fertilization
- Results in the formation of a blastocell as a result of cavitation
- Requires Na and K-ATPase transport
4) Embryo is referred to as blastocyst at this stage (58 cells)
78
Describe and compare trophoblast cells and cells in the inner cell mass
Trophoblast = outerlayer of cells of blastocyst
-Forms extraembryonic structures including placenta
Inner cell mass = inner mass of cells of blastocyst
-Forms embryo proper and some extraembryonic structures
79
Define Blastocoel
Fluid filled cavity of blastula and results from cleavage of oocyte after fertilization
- Creates polarization
- Embryonic Pole = @ location of inner cell mass
- Abembryonic Pole = Marks opposite pole
80
Compare genetic control of cleavage between mammalian and non-mammalian embryos
1) Non-mammalian vertebrates
- Early controls of cleavage via gene products transcribed from maternal genome
- Embryonic gene products often don’t appear until after blastulation
2) Mammalian Embryo
- Mammalian gene products are produced but generally degraded by 2 cell stage of development
- By the four cell stage, most transcription is via embryonic genome
81
Describe the methylation cycle in mammalian gametes and embryo
1) DNA of mature eggs and sperm is highly methylated
2) Demethylation of maternal and parental genomes occurs shortly after fertilization until the early morula
3) Remethylation of inner cell mass occurs until late blastocyst state
4) Methylation levels fall after primordial germ cells enter genital ridges
5) Remethylation occurs later during gametogenesis and may lead to maternal/parental imprinting
82
Cdx-2
Essential for trophoblast cell differentiation and antagonistic toward Oct-4
83
Oct-4
Oocyte and Zygotes express in order to permit cleavage to proceed to 2 cell stage along with Oct-4
84
All morula cells express what?
Oct-4
85
Nanog
Produced by inner cells in late morula stage and maintains integrity of inner cells along with Oct-4
86
What occurs when Nanog is absent
Inner cells differentiate into ectoderm
87
What occurs when Oct-4 is absent
Inner cells differentiate into trophoblast
88
Sox-2
-First expressed in 8 cell stage along with Oct-4 it helps control regulation of genes involved in differentiation
89
Define Regulation
Refers to ability of embryo to compensate for removal of structures or for addition of structures
90
Barr Bodies
Inactive X chromosome
| -Tells us about the basis for the sex chromatin
91
Define regulation
Refers to ability of embryo to compensate for removal of structures or for addition of structures
92
Fraternal (dizygotic) twins
Fertilization of two ovulated eggs and mechanisms of formation involves endocrine control of ovulation
93
Identical (monozygotic) twins
Product of a single fertilized egg. Unite from subdivision and splitting of a single embryo
94
Conjoined twins
Incomplete separation of portions of an embryo although two embryos take shape.
They are joined by a tissue bridge
95
Parasitic Twin
Complete portion of body protrudes from the body of an otherwise normal host twin
*Partial secondary fusion of originally separated portions of inner cell mass or formation of two primitive streaks in single embryo
96
Bateson’s Rule
Duplicated structures that are joined are marrow image of the other
97
Define Homeobox-Containing genes
Genes that contain a highly conserved sequence of 180 nucleotides called the homeobox which codes for the 60 amino acid homeodomain transcription factor proteins
98
Homeobox vs homeodomain
Homeobox = codes for the 60 amino acid homeodomains found in homeodomain transcription factor proteins
Homeodomain: Made up of 60 AA
99
What role do homeobox-containing genes play in vertebrate development
Cranio-caudal segmentation, not only along main body axis but with in the development of many organs
100
In regards to homeobox-containing genes, what differentiate loss-of-function mutations and gain-of-function mutations
1) Loss-of-Function: Result in posterior to anterior transformations
2) Gain-of-function mutations: Result in anterior to posterior transformations
101
Describe the organization of the human Hox complex
1) Genes on the 3’ ends of each of the complexes are expressed eariler and more anteriorly than those on the 5’ right
102
Destruct Homeobox-Containing Genes: T-box genes(Tbx), Helix-loop-helix genes, Forkhead (Fox) genes
1) T-box genes (Tbx) - Plays a role in inducing mesodermal germ layer and in coordinating the outgrowth of the arm or leg
2) Helix-loop-Helix genes: Code for helix-loop-helix transcription factors that are involved in homodimerization and heterodimerization and important for myogenesis
3) Forkhead (Fox) genes: Type of Helix-Loop-Helix family and is expressed in many developing organs through the the body
103
Compare the Hox gene complex in mammals to that in Drosophila
1) The mammalian Hox genes are similar in sequence to the homeotic genes found in Drosophila, and they are in the same order
104
Describe the helix-loop-helix and zinc finger transcription factor motif
1) Helix loop helix: Basic regions of proteins bind to DNA; Can be found as hetero or homodimer; important for myogenesis
2) Zinc Finger: Proteins have Zinc ions bound to polypeptide chain that cause the chain to form finger-like projections that can be inserted into the DNA helix
105
List the characteristics of Sox genes and WT1
1) Both are Gene families for Zinc Fingers
2) Sox genes: Transcribe transcription factors that have a high-mobility group domain that binds to minor groove on DNA rather than major groove; Involved in sex determination
3) WT1: Important in development of embryonic kidney and the adult kidney. Knock out WT1 cards Wilms tumor in children
106
What is a morphogen
A protein that varies in concentration and causes different developmental responses as a result of the concentration differences
107
Describe the function of each of the following sets of genes in the development of Drosophila body plan: Egg polarity genes, gap genes, pair-rule genes, segment-polarity genes, antennapedia-complex genes, and bithorax complex genes
1) Egg Polarity Genes: These genes are transcribed into mRNA in the ovary during egg formation and are translated into proteins after fertilization (genetic maternal effect); Establish the dorsal-ventral axis and anterior posterior axis
2) Gap genes: Delete adjacent segments
3) Pair-rule genes: Delete same part of pattern in every other segment
4) Segment-polarity genes: Affect polarity of segment
5) Antennapedia complex: Affects development of head and thorax
6) Bithorax Complex Genes: Affects development of posterior thorax and abdominal segments
108
SIGNALING FACTOR FAMILIES
1) Transforming Growth Factor-B Superfamily
2) Fibroblast Growth Factor Family
3) Hedgehog Family
4) Wnt Family
109
True or False; Hedgehog and Wnt families are apart of the growth factor family
True
110
Fibroblast growth factor and TGF-B factor receptors possess what type of receptor activity?
1) Protein Kinase Activity
2) Receptors for FBF possesses tyrosine kinase activity
3) Receptors for TGF-B factors possesses serine/theronine kinase-activity
111
List examples of signaling pathways
1) Delta Notch
2) Receptor Tyrosine Kinase Pathway
3) Hedgehog pathway
4) Wnt Signaling pathway
5) MicroRNA pathway
6) Retinol Pathway
112
Describe the Delta Notch Pathway
1) Delta binds to notch
2) The complex binds to suppressor of hairless
3) Notch-Deltex-Suppressor of hairless complex binds to enhancer of split
4) Resultant inhibitory signal expresses Gene expression
113
Hedgehog pathway
1) hedgehog protein complexes with cholesterol
2) Shh-cholesterol is trans located to cell surface via action of Dispersed
3) Shh-cholesterol inhibits the inhibitory actions of patched on smoothened on the target cell
4) Uninhibited smoothened signals the release of transcription Gli form a complex on Microtubule
5) Gli trans locates to the nucleus and influences gene expression
114
What occurs in the absence of Wnt?
B- catering are bound to an intracellular destruction complex within the target cell
115
Pathway for Wnt signaling
1) Wnt molecule (ligand) binds to Frizzled on target cell
2) Frizzled interacts with intracellular disheveled
3) Disheveled prevents the degradation of the B-catenins by the destruction complex
4) B-catenins translocations to nucleus and activates transcription factors
116
What are the two major groups of miRNA
Piwi-interacting RNAs: Acts during gametogenesis (esp. Spermatogenesis)
Endogenous small interfering TNAs (Endo-siRNAs): Expressed in somatic tissues throughout development
117
Roles of Dicer and Argonauts (AGO) Proteins
1) Dicer cleaves miRNA precursors
| 2) AGO binds to miRNA and creates a complex and then cleaves target mRNA
118
What is another name for retinol
Vitamin A
119
Describe the Retinol Pathway
1) Retinol binds to retinol-binding protein (RBP)
2) Complex binds to membrane RBP
3) Retinol is released into cytoplasm and binds to a CRBP 1
4) Complex trans locates into nucleus
5) Retinoic acid binds to Dimer RCR-RAR which binds to RARE which activates transcription
120
Uterine Tube Transport Timeline
1) End of day 1: 2-cell stage in isthmus
2) Day 3: Morula is in the isthmus and corona radiata is lost by this time
3) Day 4: Blastocyst is in the uterus
4) Day 5: Loss of Zona Pellucida
5) Day 6: Beginning of implantation
121
What long is the Zona Pellucida around?
Until the developing embryo reaches the uterus and then shedding of the ZP is accomplished through blastocyst hatching
