Exam 1 Flashcards
(107 cards)
1
Q
What is the site of origin of the primordial germ cells in the early mammalian embryo?
A
Yolk sac
2
Q
Morphogenesis
A
Generation of form or assumption of new shape
3
Q
Differentiation
A
Complex of changes involved in progressive specialization of structure and function, often resulting in the formation of luxury molecules
4
Q
Determination
A
Process by which a cell or part of an embryo becomes restricted to a give developmental pathway
5
Q
Ontogeny
A
Study of developmental processes from conception to death
6
Q
At what sub-stage of meiosis I does pairing of homologous chromosomes occur?
A
Zygotene
7
Q
At what stage of meiosis I does crossing-over occur?
A
Begins in pachytene, continues in diakinesis, and is completed in Diplotene.
8
Q
Compare trisomy, monosomy, aneuploidy, and polyploidy and explain how they relate to human gametogenesis.
A
Nondisjunction (uneven separation during meiosis) leads to aneuploidy (abnormal number of chromosomes). This can be trisomy (1 more chromosome, 47 instead of 46) or monosomy (1 less chromosome, 45 instead of 46). Polyploidy is a type of euploidy (good thing) that involves more than two complete sets of chromosomes.
9
Q
During oogenesis, when does the first meiotic arrest occur?
A
In diplotene, right after birth.
10
Q
During oogenesis, when does the second meiotic arrest occur?
A
The second metaphase.
11
Q
Describe the oogonium in the ovary during the early fetal period with relation to meiotic stage and cellular makeup of the follicle.
A
Fetal period: oogonium, no follicle
mitosis
Before or at birth: primary oocyte, primordial follicle, meiosis in progress
After birth: primary oocyte, primary follicle, arrested in diplotene stage
After puberty: primary oocyte, secondary follicle, first meiotic division completed, start of second division
Secondary oocyte + polar body I, tertiary follicle, ovulation
Secondary oocyte + polar body I, ovulated ovum, arrested at metaphase II
Fertilized ovum + polar body II, fertilization , second meiotic division completed
12
Q
Which hormone is required for rapid transport of the egg through the isthmus of the oviduct?
A
Progesterone.
13
Q
What is the maximum number of germ cells present in the early female embryo, and how do these numbers change throughout the lifetime of the individual?
A
7 million in the early female embryo 2 million at birth 400,000 shortly after birth 40,000 survive to puberty 400 will actually be ovulated
14
Q
What is the fate of most of the female germ cells?
A
Most will become atretic (degenerate).
15
Q
Describe the oocyte at the time of ovulation.
A
During ovulation, the egg is release from the ovary.
16
Q
What is the role of LH in resumption of meiosis? How is this related to MPF?
A
The LH surge causes the shut down of gap junctions between granulosa cell and oocyte, allowing meiosis to resume. cAMP concentration is reduced, allowing activation of MPF.
17
Q
Distinguish between theca interna and externa and their relationships to angiogenesis factor and to LH receptors and testosterone?
A
Theca externa produces angiogenesis factor while the theca interna has LH receptors and secretes testosterone.
18
Q
What components of the Graafian follicle form the corpus luteum?
A
Residual theca and granulosa cells.
19
Q
What is the function of aromatase?
A
Converts testosterone into 17-B estradiol.
20
Q
What hormone stimulates formation of LH receptors on granulosa cells?
A
Estrogen.
21
Q
The principal energy source for ejaculated spermatozoa is:
A. Prostatic acid phosphatase
B. Internal glucose
C. Prostatic citric acid
D. Fructose in seminal vesicle fluid
E. Glycogen released from the vaginal epithelium
A
D. Fructose in seminal vesicle fluid
22
Q
Of the barriers to sperm survival and transport within the female reproductive tract, low pH is the most important in the: A. Upper uterine tube B. Lower uterine tube C. Uterine cavity D. Cervix E. Vagina
A
E. Vagina
23
Q
List the types of cells involved in spermatogenesis and indicate whether they are haploid or diploid.
A
Primordial germ cells (2N) Spermatogonia (2N) Primary spermatocytes (2N) Secondary spermatocytes (N) x 2 cells Spermatids (N) x 4 cells
24
Q
Which of the cellular stages of spermatogenesis lie outside the blood-testis barrier?
A
The first meiotic division and becoming primary spermatocytes are located outside the blood-testis barrier.
25
Functions of Sertoli cells.
Physical support and maintenance
Maintain and coordinate spermatogenesis
Secrete inhibin, estrogen, and anti-mullerian factor
Maintain blood testis barrier
Secrete tubular fluid
Phagocytize residual bodies of sperm cells
26
Functions of cells of Leydig.
Produce testosterone from cholesterol.
27
LH
LH binds to LH receptors on the surface of Leydig cells, and stimulates the synthesis of testosterone from cholesterol.
28
FSH
Stimulates Sertoli cells.
29
Estrogen
Gets converted from testosterone, diffuses back to Leydig cells.
30
Testosterone
Stimulates the formation of a new blood testis barrier closer to the basal lamina.
31
Inhibin
Inhibits FSH secretion.
32
What changes to sperm occur in the head of the epididymis?
Maturation occurs, changes in glycoproteins in plasma membrane
33
A surge in which hormone level occurs 24 hours prior to ovulation?
LH
34
Describe the fate of the Graafian follicle after ovulation both in the event of fertilization and in the event of the absence of fertilization.
IF FERTILIZATION DOES NOT OCCUR:
The corpus luteum regresses and levels of progesterone and estradiol decrease, resulting in the beginning of the next menstrual phase. Inhibin inhibits the secretion of gonadotropins resulting in the regression of the corpus luteum. Replacement of the granulosa lutein cells with scar tissue.
IF FERTILIZATION DOES OCCUR:
Chorionic gonadotropin from future placental tissues maintains functional corpus luteum. Granulosa lutein cells are replaced by theca lutein cells. Corpus luteum remains functional for several months.
35
What is the role of inhibin in relation to the ovarian cycle?
Inhibin inhibits secretion of gonadotropins, especially FSH resulting in regression of the corpus luteum.
36
What is the most likely site of fertilization?
In the ampulla. In the upper 3rd of the uterine tube.
37
Compare fertilization and menstrual age with regard to establishing the age of the embryo.
Fertilization age: dates age of embryo from time of fertilization
Menstrual age: dates age of embryo from start of mother’s last menstrual period
38
What is the purpose of capacitation?
It is required for sperm to undergo arcosomal reaction.
39
Where does capacitation occur in the female tract?
Occurs inside the uterine tube in the isthmus.
40
What are the mechanisms involved in capacitation?
Removal of cholesterol from sperm surface, which acts to inhibit premature capacitation.
Removal of glycoproteins.
41
What is the major action of hyaluronidase?
it helps to breakdown the hyaluronic acid component of the intracellular matrix between the corona radiata cells.
42
zygote
The single celled stage at which the male and female pronuclei have fused together and share a common membrane.
43
With regard to fertilization, what are the characteristics of the fast block to polyspermy?
Consists of a rapid depolarization of egg plasmalemma.
May last a little longer in mammals.
Temporarily prevents polyspermy and allows time for egg to establish the slow block.
44
With regard to fertilization, what are the characteristics of the slow block to polyspermy?
Mostly characterized by release of polysaccharides from the cortical granules located under the plasmalemma of the egg.
45
What roles do ZP3 and phospholipase C zeta play in egg activation?
ZP3: stimulates acrosomal reaction, mediates attachment of sperm to the ZP
Phospholipase C zeta: introduced by sperm and initiates metabolic activation of egg by release of calcium ion with in egg cytoplasm
46
What ion initiates metabolic activation of the egg? What are the results of this activation?
Calcium initiates metabolic activation
Released calcium initiates blocks to polyspermy, stimulates increase in egg respiration and metabolism via the sodium-hydrogen ion exchange mechanism, and results in an increase in pH and an increase in oxidative metabolism
47
Describe the relationship and functions of each of the following hormones to the menstrual cycle—both the ovarian aspect of the cycle and the uterine aspect of the cycle.
GnRH, LHRH: stimulates release of LH and FSH by posterior pituitary
Prolactin inhibiting factor: inhibits release of prolactin by anterior pituitary
FSH: stimulates follicle cells to produce estrogen
LH: stimulates follicle cells and corpus luteum to produce progesterone
Estrogen: has multiple effects on reproductive tract, breasts, body fat, and bone growth
Progesterone: has multiple effects on reproductive tract and breast development
Testosterone: precursor for estrogen biosynthesis, includes follicular atresia
Inhibin: inhibits FSH secretion, has local effects on ovaries
Activin: stimulates granulosa cell proliferation
17B-estradiol: sharp rise causes preovulatory surge of LH and FSH
48
What is the relation of Oct-4 to early cleavage?
Required to permit cleavage and proceed to 2 cell stage
49
What gene(s) is/are involved in the initiation of cleavage and the first cleavage division?
Oct-4
50
Describe the general structure of the blastocyst, including the different components.
Surrounded by ZP
Consists of two cells types:
outer layer of cells = trophoblast
inner mass of cells = inner cell mass
51
Describe the role of specific transcription factors in the subdivision of the inner cell mass into epiblast and hypoblast.
Cells entering inner cell mass earliest express Nanog and are destined to become Epiblast cells; cells entering inner cell mast later express Gaga 6 and are destined to become hypoblast cells.
52
At what point in development does most transcription via the embryonic genome begin to occur?
By the four cell stage.
53
Be familiar with the methylation cycle and know at what point during early development would methylation be lowest in both the maternal and paternal chromosomes.
Methylation is the addition of methyl groups to specific regions of DNA molecules; it inactivates genes.
DNA of mature eggs is highly methylated.
Demethylation of maternal and paternal genomes occurs shortly after fertilization until the early morula
Methylation levels fall after primordial germ cells enter genital ridges
54
```
What is the most common condition associated with spontaneously aborted embryos?
A. Maternal imprinting
B. Paternal imprinting
C. Ectopic pregnancy
D. Chromosomal abnormalities
E. Lack of X-chromosomal inactivation
```
D. Chromosomal abnormalities
55
Inside-out hypothesis
Fate of blastomere is determined by its position within the embryo, not from intrinsic properties
56
Cell polarity model
Depends on plane of cell division during cleavage
Cleavage plane parallel to the other surface of the embryo:
-Outer daughter cell --> trophoblast cell (polar)
-Cells pick up a path of outer cell membrane containing microvilli and ezrin
-Inner daughter cell --> inner cell mass (apolar)
Cleavage plane perpendicular to outer surface of the embryo
-Both daughter cells become trophoblast cells
57
Nanog
Produced by inner cell in late morula stage
Maintains integrity of inner cell mass along with Oct-4
Without Nanog inner cells differentiate into endoderm
Without Oct-4 inner cells differentiate into trophoblast
58
Sox2
First expressed in 8-cell stage
| Along with Oct-4 it helps to control regulation of genes involved in differentiation
59
Oct-4
Expressed in developing oocytes and zygote
Required to permit cleavage to proceed to 2-cell stage
Expressed in all morula cells
May play a role in the maintenance of the undifferentiated state
60
Prader-Willi syndrome
```
Small hands and feet
Short stature
Poor sexual development
Mental retardation
Voracious appetites (usually obese)
Maturation is always inherited from father
-Deletion in long arm of chromosome 15
```
61
Angelman Syndrome
```
Exhibit frequent laughter
Uncontrolled muscle movement
Large mouth
Unusual seizures
Mutation is always inherited from mother
-Deletion is long arm of chromosome 15
```
62
What does Bateson’s rule refer to?
When duplicated structures are joined during critical developmental stages , one structure is the mirror of the other (think conjoined twins)
63
Regulation
Refers to ability of embryo to compensate for removal of structures or for addition of structures.
64
When does X-inactivation take place in humans?
During the 1st few weeks of development.
65
What role does Xist play in X-inactivation?
Xist brings along the action of X inactivation by producing an RNA molecule that coats the X chromosome and induces X-inactivation.
66
Describe the Barr body and numbers in normal male and female individuals and in individuals with abnormal numbers. Relate this to chromosome number in humans.
Barr Body = inactive X chromosome. X-inactivation is an example of dosage compensation and provides equal expression of X chromosome products in both male and females. Female (XX) have 1 Barr body and Male (XY) have 0 Barr bodies.
67
```
What tissue from implanting embryo directly interfaces with the endometrial connective tissue?
A. Corona radiata
B. Inner cell mass
C. Extraembryonic mesoderm
D. Epiblast
E. Syncytiotrophoblast
```
E. Syncytiotrophoblast
68
```
Identical twinning in made possible by what process property of the early embryo?
A. Regulation
B. Aneuploidy
C. Paternal imprinting
D. Maternal imprinting
E. X-chromosomal inactivation
```
A. Regulation
69
The Zona pellucida:
A. Aids in penetration of the endometrial epithelium
B. Serve as a source of nutrients For the embryo
C. Prevents premature implantation of the cleaving embryo
D. All of the above
E. None of the above
C. Prevents premature implantation of the cleaving embryo
70
Describe the trophoblast and relate to its two main divisions. Which division directly interfaces with the endometrial connective tissue?
Trophoblast separates into a cellular cytotrophoblast and a multinucleated syncytiotrophoblast. Syncytiotrophoblast projection penetrate the endometrial basal lamina and the begin to invade the endometrial stroma.
71
Describe the process of implantation.
Attachment of expanded blastocyst to the endometrial epithelium
Penetration of the uterine epithelium
Invasion into tissues underlying the epithelium
Erosion of the maternal vascular supply
72
What is the most common site for ectopic pregnancy?
Ampulla
73
Decidual reaction
The response of the endometrial stroma cells to the invading blastocyst. W/o decidual reaction, the trophoblast potentially might rode all the way through the endometrial wall.
74
```
Which of the following signaling pathways is often involved in lateral inhibition?
A. Hedgehog
B. Delta notch
C. Wnt
D. Receptor tyrosine kinase
E. Retinol
```
B. Delta notch
75
```
TGF-B often utilizes which of the following kinds of pathways?
A. Hedgehog
B. Delta notch
C. Wnt
D. Receptor tyrosine kinase
E. Retinol
```
D. Receptor tyrosine kinase
76
Describe functions of the egg-polarity, gap, pair-rule, segment polarity, and homeotic genes in Drosophila.
Egg polarity genes are transcribed into mRNAs in the ovary during egg formation. The mRNAs migrate into the eggs and are translated into proteins after fertilization (example of genetic maternal effect)
Gap genes delete adjacent segments
Pair rule genes delete same part of pattern in every other segment
Segment polarity genes affect polarity of segment
Homeotic genes determine the identity of individual segments; products of homeotic genes activate other genes that encode these segment-specific characteristics
77
What signaling factor family is related to the segment polarity molecules in Drosophila?
Hedgehog family
78
Describe the MiRNA pathway and its components.
Small RNAs are small non coding RNAS that influence gene expression.
2 major groups of miRNAS: piwi-interacting RNAs (piRNAs)- act during gametogensis. Endogenous small interfering RNAs (endo-siRNAs) - expressed in somatic tissues throughout development.
Components of pathway include Dicer and AGO (the argonauts protein)
79
Describe the interrelationships among the Dorsal protein, Cactus protein, and Toll protein in establishing the dorsal-ventral axis of Drosophila.
Dorsal protein is a product of the dorsal gene and is expressed in the ovary; cactus protein is also expressed in the ovary and binds to the dorsal protein and traps it in the cytoplasm; Toll protein is also expressed in the overlay and leads to the degradation of the cactus protein, allowing the dorsal protein to move to the nuclei of the ventral cells.
80
Which genes in Drosophila play a role in the establishment of the anterior-posterior axis?
Bicoid, Nanos, and hunchback
81
Zinc-finger transcription factors are associated with which gene family?
Sox genes and WT1
82
What is a morphogen?
Protein that varies in concentration and causes developmental responses as a result of the concentration differences.
83
What are bottle cells and what role do they play in gastrulation?
As the cells enter the primitive streak they elongate and lose their basal lamina making them appear bottle like
When they become free of the epiblastic layer in the primitive groove, they assume characteristic of mesenchymal cells
84
What are the two major signaling molecules that play a role in the formation of the primitive streak?
TGF-B and Wnt
85
What tissues are derived from the hypoblast?
Extraembryonic endoderm
| Yolk sac endoderm
86
What tissues are derived from the epiblast?
Ectoderm
Mesoderm
Endoderm
87
When does gastrulation occur in humans?
At the end of the second week of gestation
88
```
During oogenesis there are 2 meiotic arrests. The first meiotic arrest occurs at which of the following states of meiosis?
A. Diplotene stage of prophase I
B. Diakinesis stage of prophase I
C. Metaphase I
D. Anaphase I
E. Metaphase II
```
A. Diplotene stage of prophase I
89
```
Primordial germ cells migrate from their point of origin in the very early embryo into the developing gonads. In mammalian embryos and many other vertebrate embryos, the primordial germ cells originate from and are first observed in which of the following locations?
A. Hindgut
B. Dorsal mesentary
C. Primitive streak
D. Yolk sac
E. Chorion
```
D. Yolk sac
90
Which of the following best describes the oogonium in the ovary during the early fetal period?
A. Haploid oogonium with a single layer of cuboidal follicle cels
B. Diploid oogonium with no follicle cells
C. Haploid oogonium with no follicle cells
D. Diploid oogonium with a few flattened follicle cells
B. Diploid oogonium with no follicle cells
91
```
In meiosis, pairing of homologous chromosomes begins during which of the following stages of prophase 1?
A. Leptotene
B. Zygotene
C. Patchytene
D. Diplotene
```
B. Zygotene
92
```
Which of the following refers to the process by which a cell of part of an embryo becomes restricted to a given developmental pathway?
A. Morphogenesis
B. Differentiation
C. Ontogeny
D. Determination
```
D. Determination
93
```
After the 1st meiotic arrest, the secondary oocyte resumes meiosis at the time ovulation. This resumption of meiosis is enabled by closure of gap junctions between granulosa cells and the oocyte, resulting in a reduction in the flow of cAMP into the oocyte. Which of the following is responsible for shutting down the gap junctions?
A. LH
B. FSH
C. Progesterone
D. Estrogen
```
A. LH
94
```
Capacitation involves the removal of cholesterol and glycoproteins from the sperm surface. It is necessary the sperm to fertilize the egg. Capacitation occurs in which part of the following location?
A. Isthmus of the oviduct
B. Ampulla of the oviduct
C. Epididymus
D. Vas deferens
```
A. Isthmus of the oviduct
95
```
During spermatogenesis, histone is replaced by which of the following, to allow better packing of the condensed chromatin in the head of the spermatozoon?
A. Inhibin
B. Prostaglandin E
C. Testosterone
D. Protamine
E. Androgen-binding protein
```
D. Protamine
96
```
Which cell type is located outside the blood-testis barrier?
A. Spermatozoon
B. Secondary spermatocyte
C. Spermatid
D. Primary spermatocyte
E. Spermatogonium
```
E. Spermatogonium
97
```
Which of the following cells normally participates in mitotic divisions?
A. Primary oocyte
B. Oogonium
C. Primary spermatocyte
D. Spermatid
E. Secondary spermatocyte
```
B. Oogonium
98
```
Which of the following is a transcription factor?
A. FGF
B. Pax
C. TGF
D. Notch
E. Wnt
```
B. Pax
99
```
A mutation in what receptor is the basis for basal carcinomas of the skin?
A. Patched
B. Retinoic Acid
C. Notch
D. FGF receptor
E. None of the above
```
A. Patched
100
```
Zinc finger or helix-loop-helix arrangements are characteristic of members of what class of molecules?
A. Proto-oncogenes
B. Signaling molecules
C. Receptors
D. Transcription factors
E. None of the above
```
D. Transcription factors
101
```
Based on your knowledge of paralogous groups, which gene would be expressed most anteriorly in the embryo?
A. Hoxa-13
B. Hoxc-9
C. Hoxd-13
D. Hoxb-1
E. Hoxb-6
```
D. Hoxb-1
102
Sonic hedgehog is produced on which signaling center?
A. Notochord
B. Intestinal portals
C. Floor plate of neural tube
D. Zone of polarizing activity in the limb bud
E. All of the above
E. All of the above
103
```
The principal inducer in primary neural induction is the:
A. Hypoblast
B. Primitive streak
C. Extraembryonic mesoderm
D. Notochordal process
E. Embryonic ectoderm
```
D. Notochordal process
104
```
Which of the following tissues arises from cells passing through the primitive streak?
A. Embryonic mesoderm
B. Hypoblast
C. Cytotrophoblast
D. Primary yolk sac
E. Amnion
```
A. Embryonic mesoderm
105
```
Cells of which germ layer are NOT present in the oropharyngeal membrane?
A. Ectoderm
B. Mesoderm
C. Endoderm
D. All are present
```
B. Mesoderm
106
```
The prechordal plate plays an important role in regionalization of the:
A. Notochord
B. Forebrain
C. Embryonic mesoderm
D. Primitive node
E. Hindbrain
```
B. Forebrain
107
```
Brachyury, a deficiency in caudal tissues in the body is caused by a mutation in what gene?
A. Lim-1
B. Noggin
C. T
D. Sonic hedgehog
E. Activin
```
C. T
