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Embryo > Exam 1 Embryo Review > Flashcards

Exam 1 Embryo Review Flashcards

1
Q

Principal energy source of ejaculated spermatozoa is:

a. Prostatic acid phosphatase
b. Internal glucose
c. Prostatic citric acid
d. Fructose in seminal vesicle fluid
e. Glycogen released from vaginal epithelium

A

Fructose in Seminal Vesicle Fluid

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2
Q 
Of barriers of sperm survival and transport within female reproductive tract, low pH is most important in:
a. Upper uterine tube
B. Lower uterine tube
C. uterine cavity
D. Cervix
E. Vagina
A

Vagina

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3
Q

What is most common condition associated w/ spontaneously aborted embryos?

A.Maternal imprinting
b.Paternal imprinting
c.Ectopic pregnancy
D. Chromosomal abnormalities 
E. Lack of chromosomal inactivation
A

Chromosomal abnormalities

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4
Q

What tissue from implanting embryo directly interfaces w/ endometrial connective tissue?

a. Corona radiata
b. Inner cell mass
c. Extraembryonic mesoderm
d. Epiblast
e. Syncytiotrophoblast

A

Syncytiotrophoblast

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5
Q

Identical twinning is made possible by what process or property of early embryo?

a. Regulation
b. Aneuploidy
c. Paternal imprinting
d. Maternal imprinting
e. X-chromosomal inactivation

A

Regulation

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6
Q

Zona pellucida:

a. Aids in penetration of endometrial epithelium
b. Serves as source of nutrients for embryo
c. Prevents premature implantation of cleaving embryo
d. All of the above
e. None of the above

A

Prevents premature implantation of cleaving embryo

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7
Q

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

A

Delta. Notch

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8
Q

TGF-beta often utilizes which of the following kinds of pathways?

a. Hedgehog
b. Delta notch
c. Wnt
d. Receptor tyrosine kinase
e. Retinol

A

Receptor Tyrosine kinase

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9
Q

A mutation of what receptor is basis for basal carcinomas of the skin?

a. Patched
b. Retinoic acid
c. Notch
d. FGF receptor
e. None of the above

A

Patched

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10
Q

During oogenesis there are two meiotic arrests. The first meiotic arrest occurs at which of the following stages of meiosis

A

Prophase I (diplotene)

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11
Q

In mammalian embryos and many other vertebrate embryos, the primordial germ cells originate from and

A

Yolk sac

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12
Q

Which of the following best describes the oogonium in the ovary during the early fetal period?

A

a. Diploid oogonium w/ no follicle cells

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13
Q

In meiosis, pairing of homologous chromosomes begins during which of the following stages of prophase I?

a. Zygotene
b. Leptotene
c. Pachytene
d. Diplotene

A

Zygotene

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14
Q

Which of the following refers to the process by which a cell or part of an embryo becomes restricted to a given developmental pathway?

a. Morphogenesis
b. Differentiation
c. Ontogeny
d. Determination

A

Determination

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15
Q

Which of the following is responsible for shutting down gap junctions?

a. LH
b. FSH
c. Progesterone
d. Estrogen

A

LH

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16
Q

Capacitation occurs in which part of the following locations

a. Isthmus of oviduct
b. Ampulla of oviduct
c. Epididymis
d. Vas deferens

A

Isthmus of oviduct

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17
Q

During transport of the egg through the female tract following ovulation, most likely site of fertilization is which?

A

Ampulla

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18
Q

Which of the following cell types is located outside blood-testis barrier?

a. Primary spermatocyte
b. Spermatid
c. Secondary spermatocyte
d. Spermatozoa
e. Spermatogonium

A

Spermatogonium

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19
Q

Which of the following type of cells in male converts testosterone to estrogen?

a. Cells of Leydig
b. Sertoli cells
c. Interstitial cells
d. Spermatogonia

A

Sertoli Cells

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20
Q

Rapid transport of egg through isthmus of oviduct requires which of the following hormones?

a. LH
b. FSH
c. Progesterone
d. Estradiol

A

Progesterone

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21
Q

Which of the following cells are responsible for production of testosterone in testes?

a. Sertoli cells
b. Leydig cells
c. Granulosa
d. Spermatogonia cells

A

Leydig Cells

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22
Q

Endometrial growth increases endometrial thickness from 1-2mm to 8-10 mm by day 14. This
proliferation phase of the uterine cycle is the result of secretion of which of the following hormones by granulosa cells?
a. LH
b. Estradiol
c. Progesterone
d. FSH

A

Estradiol

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23
Q

Graafian follicle in addition to participating in ovulation, also has endocrine functions. What
components of graafian follicle form corpus luteum?
a. Granulosa cells
b. Thecal cells
c. Corona radiata cells
d. Both granulosa and thecal cells

A

Both granulosa and thecal cells

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24
Q

Inhibin, released by granulosa cells during ovarian cycle, inhibits secretion of gonadotropins, especially FSH, resulting in which of the following:

a. Proliferative phase of endometrial cycle
b. Replacement of granulosa lutein cells w/ thecal lutein cells
c. Regression of corpus luteum
d. Ovulation

A

Regression of corpus luteum

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25
Q

During menstrual cycle, sharp spike in plasma levels of which of the following hormone just before ovulation is responsible for ovulation?

a. FSH
b. LH
c. Estrogen
d. Progesterone

A

LH

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26
Q 
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
A

Hoxb-1

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27
Q

Principal inductor in primary neural induction is the:

a. Hypoblast
b. Primitive streak
c. Extraembryonic mesoderm
d. Notochordal process
e. Embryonic ectoderm

A

Notochordal Process

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28
Q

Cells of which germ layer are not present in oropharyngeal membrane?

a. Ectoderm
b. Mesoderm
c. Endoderm
d. All are present

A

Mesoderm

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29
Q

Brachyury, a deficiency in caudal tissue sin body is caused by mutation in what gene?

a. Lim-1
b. Noggin
c. T (tails)
d. Sonic hedgehog
e. Activin

A

T (tails)

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30
Q

Hypoblast of bilaminar early embryo gives rise to which of following tissue types?

a. Embryonic endoderm only
b. Extraembryonic endoderm only
c. Both embryonic and extraembryonic endoderm
d. Both extraembryonic endoderm and mesoderm

A

Extraembryonic endoderm only

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31
Q

Splitting of blastocyst during early development resulting in two complete but separate blastocysts enclosed within single trophoblast is common mode of twining. Assuming that completely normal identical twins result, what developmental property is illustrated?

a. Differentiation
b. Determination
c. Regulation
d. Morphogenesis

A

Regulation

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32
Q

Which of the following is thought to be one of the 2 signaling molecules that plays a role in formation of primitive streak?

a. TGF-beta
b. Retinoic acid
c. Shh
d. Chordin

A

TGF-beta

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33
Q

In one type of signaling pathway, a dominant cell expresses Delta, which binds to receptors on needing cells, What is the receptor for delta in this pathway?

a. Tyrosine kinase
b. STAT
c. Notch

A

Notch

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34
Q

In mammalian embryos, unlike non mammalian and invertebrate, most transcription via embryonic genome, as opposed to maternal genome, occurs as early as which of the following stages?

a. Zygote
b. 4-cell stage
c. Blastula
d. Gastrula

A

4-cell stage

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35
Q 
In Drosophila, from which of the following gene categories are mRNAs derived from maternal
genome rather than embryonic genome?
a. Pair-rule genes
b. Homeotic genes
c. Egg-polarity genes
d. Gap genes
A

Egg-polarity genes

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36
Q

Which of the following is a transcription factor?

a. FGF
b. Pax
c. TGF
d. Notch
e. Wnt

A

Pax

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37
Q

Zinc fingers or helix-loop-helix arrangements are characteristics of members of what class of molecules

A

Transcription factors

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38
Q

What is most common condition associated w/ spontaneously aborted embryos?

a. Maternal imprinting
b. Chromosomal abnormalities

A

Chromosomal abnormalities

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39
Q

What tissue from implanting embryo directly interfaces w/ endometrial connective tissue?

a. Corona radiata
b. Inner cell mass
c. Extraembryonic mesoderm
d. Epiblast
e. Syncytiotrophoblast

A

Syncytiotrophoblast

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40
Q

Which of the following signaling pathways is often involved in lateral inhibition?

A

Delta Notch

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41
Q
  1. TGF-beta often utilizes which of the following kinds of pathways?
A

Receptor tyrosine kinase

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42
Q

Transcription of which of the following genes is required to permit cleavage to proceed to 2-cell stage in mammalian embryos?

A

a. 4-Oct

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43
Q

Which of the following organizes the border between dorsal and ventral thalamus?

a. Prechordal plate
b. Anterior neural ridge
c. Isthmic organizer
d. Zona limitans

A

Zona limitans

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44
Q
  1. In the late primitive streak stage, which of the following signal molecules released from primitive streak activates Hox genes?
    a. Noggin
    b. FGF
    c. Chordin
    d. SHH
A

FGF

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45
Q

Which of the following pathways ensures that neural tube closure occurs?

a. Convergent extension
b. Planar cell polarity
c. Signaling pathway involving Otx-2 and Gbx-2
d. Anterior neural ridge signaling

A

Planar cell polarity

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46
Q

Which of the following is located at the junction of future midbrain and hindbrain and expresses FGF-8?

a. Prechordal plate
b. Anterior neural ridge
c. Isthmic organizer
d. Zona limitans

A

Isthmus Organizer

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47
Q

Which of the following interpretations best summarizes the effect of grafting a second dorsal lip to blastocoel of early amphibian embryo?

a. Dorsal lip can induce formation of a second embryo
b. Second dorsal lip counteracts polarizing effects of original dorsal lip

A

Dorsal lip can induce formation of a second embryo

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48
Q 
In drosophila, which of the following classes of genes is involved in deletion of adjacent
segments?
a. Gap genes
b. Pair rule
c. Segment polarity genes
d. Hox genes
A

Gap genes

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49
Q

What are the two major signaling molecules that play a role in the formation of the primitive streak?

A

TFG-B

WNT

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50
Q

What is the site of origin of the primordial germ cells in the early mammalian embryo?

A

Yolk sac

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51
Q

At what sub-stage of meiosis I does pairing of homologous chromosomes occur?

A

Zygotene (of Prohase I)

52
Q

At what stage of meiosis I does crossing-over occur

A

Prophase I (Pachytene – Diplotene)

53
Q

Compare trisomy, monosomy, aneuploidy, and polyploidy and explain how they relate to human gametogenesis.

A

Aneupoidy: abnormal number of chromosomes o -Trisomy: 3 (47 chromosomes)
-Monosomy: 1 (45 chromosomes)
Polyploidy: more than one abnormal set of chromsosmes

54
Q

During oogenesis, when does the first meiotic arrest occur?

A

Prophase I (Diplotene)

55
Q

During oogenesis, when does the second meiotic arrest occur?

A

Metaphase II

56
Q

Describe the oogonium in the ovary during the early fetal period with relation to meiotic stage and cellular make-up of the follicle.

A

Diploid oogonium with NO follice

57
Q

Which hormone is required for rapid transport of the egg through the isthmus of the oviduct?

A

Progesterone

58
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→2 million at birth→400,000 after birth→40,000 puberty→400 ovulated

59
Q
  1. What is the fate of most of the female germ cells?
A

Atretic

60
Q

Describe the oocyte at the time of ovulation.

A

Diploid primary oocyte with granulosa cells outside of follicle cells
Haploid secondary oocyte (+ haploid polar body)→2 chromatids/chromosome

61
Q
  1. What is the role of LH in resumption of meiosis? How is this related to MPF?
A
  • LH surge→shuts down gap junctions between granulosa cells and oocyte.
  • This causes cAMP concentration to be reduced which allows activation of MPF.
62
Q

Distinguish between theca interna and externa and their relationships to angiogenesis factor and to LH receptors and testosterone?

A
  • Theca externa: produce angiogenesis factor

* Theca interna: with LH receptors, secrete testosterone

63
Q

What components of the Graafian follicle form the corpus luteum?

A
  • Granulosa cells

* Residue theca

64
Q
  1. What is the function of aromatase?
A

Converts testosterone into 17B-estradiol

65
Q

What hormone stimulates formation of LH receptors on granulosa cells?

A

Estrogen

66
Q

What is the principal energy source for ejaculated spermatozoa?

A

Fructose

67
Q

With regard to the passage of sperm through the female reproductive tract, where do they encounter the lowest pH?

A

Vagina

68
Q

List the types of cells involved in spermatogenesis and indicate whether they are haploid or diploid.

A
  • Primordial germ cells (2N – Diploid)
  • Spermatogonia (2N – Diploid)
  • Primary oocytes (2N – Diploid)
  • Secondary oocytes (N – Haploid) x 2
  • Spermatids (N – Haploid) x 4
69
Q

Which of the cellular stages of spermatogenesis lie outside the blood-testis barrier?

A

Sertoli cells – barrier between forming sperm cells and the rest of the body and spermatogonia

70
Q

Describe the functions of Sertoli cells and cells of Leydig.

A
  • Sertoli cells: secrete estrogen, inhibin, anti-Mullerian factor
  • Leydig cells: produce testosterone
71
Q

What role do LH, FSH, estrogen, testosterone, and inhibin play in sperm cell production?

A
  • LH: bind receptors on Leydig cells→synthesize testosterone from cholestrol
  • FSH: bind receptors on Sertoli cells→convert testosterone into estrogen
  • Estrogen: converted from testosterone, gives sperm its reproductive punch
  • Testosterone: to get testicle to make sperm→spermatogenesis
  • Inhibin: secreted by Sertoli cells
72
Q

What changes to sperm occur in the head of the epididymis?

A

• Changes in glycoproteins in plasma membrane

73
Q

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.

A

• Ovarian Cycle
o Follicular Phase: FSH
o Ovulation Phase: FSH + LH Surge
o Luteal Phase: Estrogen + Progesterone

• Uterine/Endometrial Cycle
o Menstrual Phase: endometrial build-up from previous cycle sloughs off→period (prostaglandins → vasoconstriction)
o Proliferation Phase: Estradiol allows endometrial growth
o Secretory Phase: Estrogen decreases, endometrial growth stops, controlled by rising
levels of progesterone

74
Q

A surge in which hormone level occurs 24 hours prior to ovulation?

A

LH

75
Q

Describe the fate of the Graafian follicle after ovulation both in the event of fertilization and in the event of the absence of fertilization.

A
  • In event of fertilization: Functional corpus luteum, granulosa lutein cells replaced by thecal lutein cells and corpus luteum stays functional for several months into pregnancy
  • In absence of fertilization: Corpus luteum regresses with decrease in progesterone and estradiol→vasoconstriction = period
76
Q
  1. What is the role of inhibin in relation to the ovarian cycle?
A

Inhibits section of gonadotrophins, especially FHS, resulting in regression of corpus luteum

77
Q

What is the most likely site of fertilization?

A

Ampulla

78
Q

Compare fertilization and menstrual age with regard to establishing the age of the embryo.

A
  • Fertilization age: dates age of embryo from time of fertilization
  • Menstrual age: dates age of embryo from start of mother’s last menstrual period
  • Menstrual age is TWO WEEK GREATER than fertilization age
79
Q
  1. Describe capacitation and explain where it occurs.
A
  • Capacitation: required for sperm to undergo acrosomal reaction
  • Isthmus of the oviduct
80
Q

What is the major action of hyaluronidase?

A

Helps break down hyaluronic acid component of the intracellular matrix between corona radiate
cells

81
Q

Define “zygote.”

A

Single-celled stage at which the male and female pronuclei have fused together and share a
common membrane, establishing the diploid chromosome number

82
Q
  1. With regard to fertilization, what are the characteristics of the fast block to polyspermy?
A
  • Consists of rapid depolarization of egg plasmalemma
  • -70 to +10 mV within 2-3 seconds (can be several minutes in mammals)
  • Temporarily prevents polyspermy and allows time for the egg to establish slow block
83
Q
  1. With regard to fertilization, what are the characteristics of the slow block to polyspermy?
A

• Mostly characterized by release of polysaccharides from the cortical granules located just under
the plasmalemma of the egg

84
Q

What roles do ZP3 and phospholipase C zeta play in egg activation?

A

• ZP3:
o helps attachment of sperm to ZP
o ZP3 stimulates acrosomal reaction in mammals, by acting through G-proteins in sperm
plasma membrane
• Phospholipase C:
o Initiates release of calcium ion within egg cytoplasm

85
Q
  1. What ion initiates metabolic activation of the egg? What are the results of this activation?
A

• Calcium
o Initiates block to polyspermy
o Stimulates increase in egg respiration and metabolism via Na+/H+ exchange mechanism o Increase in pH and increase in oxidative metabolism

86
Q

What is the relation of Oct-4 to early cleavage?

A
  • Required to permit cleavage to proceed to 2-cell stage

* Without Oct-4, inner cells differentiate into trophoblast

87
Q

What gene(s) is/are involved in the initiation of cleavage and the first cleavage division?

A
  • Ccx-2
  • Oct-4
  • Nanog
  • Sox2
88
Q
  1. Describe the general structure of the blastocyst, including the different components.
A 
• Surrounded by zona pellucida
• Large, eccentrically placed blastocoel, POLARIZED
• Two types of cells:
o Outer layer of cells= Trophoblast
o Inner layer of cells= Inner cell mass
89
Q

Describe the role of specific transcription factors in the subdivision of the inner cell mass into epiblast and hypoblast.

A
  • Nanog → epiblast

* (FGF-4) → Gata-6 → hypoblast

90
Q
  1. At what point in development does most transcription via the embryonic genome begin to occur?
A

• By the four-cell stage

91
Q

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?

A

• Methylation cycle:
o DNA of mature eggs and sperm is highly methylated
o Demethylation of maternal and paternal genomes occurs shortly after fertilization until
the early morula
o Remethylation of inner cell mass occurs until late blastocyst state
o Methylation levels fall after primordial germ cells enter genital ridges
o Remethylation occurs later during gametogenesis and may lead to maternal/paternal
imprinting
• Methylation lowest: after fertilization
• Methylation is erased in the germ cells of each generation and then reestablished in the course of gamete formation

92
Q

What is the most common condition associated with spontaneously aborted embryos?

A

Chromosomal abnormalities

93
Q

Describe the inside-out hypothesis and cell polarity model theories for the establishment of polarity.

A

• Inside-Out Hypothesis: fate of blastomere is determined by its position within the embryo, not
from intrinsic properties
• Cell Polarity Model Theories: depends on the plan of cell division during cleavage
o Parallel plane to outer surface of embryo:
▪ Outer daughter cell→trophoblast cell (polar)
▪ Inner daughter cell→inner cell mass cell (apolar)
o Perpendicular plane to outer surface of embryo:
▪ Both daughter cells become trophoblast cells

94
Q

Describe the role of Nanog, Sox2, and Oct-4 in early differentiation.

A

• Nanog: produced by inner cells in late morula stage, maintains integrity of inner cell mass along
with Oct-4 (without Nanog, inner cells differentiate into endoderm)
• Sox2: first expressed in 8-cell stage, along with Oct-4 it helps to control regulation of genes
involved in differentiation
• Oct-4: required to permit cleavage to proceed to 2-cell stage, expressed in all morula cells, may
play a role in maintenance of undifferentiated state

95
Q
  1. Compare Prader-Willi and Angelman syndromes and relate to genomic imprinting.
A
  • Prader-Willi: deletion in Chr. 15 from DAD

* Angelman syndromes: deletion in Chr. 15 fom MOM

96
Q
  1. What does Bateson’s rule refer to?
A

Mendel genetics

97
Q

Define regulation and relate to twinning.

A
  • Regulation: Ability for the embryo to compensate for an additional/removal of structures
  • How identical twinning is made possible in the early embryo
98
Q

Relate number of X chromosomes to various phenotypes discussed in lecture and to Barr body formation.

A

• XX (1) , XY (0) , XO (0) , XXY (1) , XXX (2)

99
Q

When does X-inactivation take place in humans?

A

During first few weeks of development

100
Q

What role does Xist play in X-inactivation?

A

• Xist = X inactivation specific transcript→it produces an RNA molecule that coats the X
chromosome and induces X inactivation (removal of acetyl, addition of methyl)

101
Q

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.

A
  • Barr Body= inactive X chromosome
  • Females= XX (1 Barr Body)
  • Males= XY (0 Barr Body)
102
Q

What tissue from the implanting embryo directly interfaces with the endometrial connective tissue?

A

Syncytiotrophoblast

103
Q
  1. Identical twinning is made possible by what process or property of the early embryo?
A

Regulation

104
Q

Describe the trophoblast and relate to its two main divisions. Which division directly interfaces with the endometrial connective tissue?

A
  • Trophoblast: cytotrophoblast + syncytiotrophoblast

* Syncytiotrophoblast interfaces with endometrial connective tissue

105
Q

Describe the process of implantation.

A
  • Attachment of expanded blastocyst to the endometrial epithelium
  • Penetration of the uterine epithelium
  • Invasion into the tissues underlying the epithelium
  • Erosion of the maternal vascular supply
106
Q

What is the most common site for ectopic pregnancy?

A

• Ampulla

107
Q

Describe the decidual reaction and its function(s).

A

• The response of the endometrial stroma cells to invading blastocyst
• Without decidual reaction, the trophoblast potentially might erode all the way through the
endometrial wall
• Primary function: to provide an immunologically (IL-2) privileged site to protect the developing
embryo form being rejected

108
Q

Which signaling pathway is often involved in lateral inhibition?

A

Delta Notch

109
Q

Describe loss-of-function and gain-of-function mutations and give examples.

A

• Loss-of-function: posterior to anterior transformations (i.e. Ab to XIHBox injected into early frog
embryo→anterior spinal cord region into expansion of hindbrain)
• Gain-of-fuction: anterior to posterior transformations (i.e. Drosophila and mouse)

110
Q

Know which of the Drosophila genes involved in symmetry of the early embryo are derived from the maternal genome (maternal effect genes) rather than the embryonic genome.

A

Egg Polarity Genes

111
Q

Describe functions of the egg-polarity, gap, pair-rule, segment polarity, and homeotic genes in Drosophila.

A
  • Egg-polarity: Establish gradients from anterior and posterior poles of the egg
  • Gap genes: define broad regions of egg (delete adjacent segments)
  • Pair-rule genes: Define 7 segments (delete same part of pattern in every other segment)
  • Segment-polarity genes: Define 14 segments (affect polarity of segment)
  • Homeotic genes: Determine regional characteristics (identity of individual segments)
112
Q

What signaling factor family is related to the segment polarity molecules in Drosophila?

A

• Hedgehog family

113
Q
  1. Describe the MiRNA pathway and its components.
A

• Precursor miRINA cleaved by DICER→miRINA + AGO to cleave target protein

114
Q

Describe the interrelationships among the Dorsal protein, Cactus protein, and Toll protein in establishing the dorsal-ventral axis of Drosophila.

A

• Dorsal protein: expressed in ovary, becomes concentrated in nuclei on ventral surface
• Cactus protein: expressed in ovary, binds to dorsal protein and traps it in cytoplasm
• Toll protein: expressed in ovary, leads to degradation of the cactus protein, allowing dorsal
protein to move into the nuclei of the ventral cells

115
Q

Which genes in Drosophila play a role in the establishment of the anterior-posterior axis?

A
  • Bicoid
  • Nanos
  • Hunchback
116
Q
  1. Zinc-finger transcription factors are associated with which gene family?
A
  • Sox genes **

* WT1

117
Q

What are bottle cells and what role do they play in gastrulation?

A

• Cellular motility is a ubiquitous biological phenomenon that occurs constantly throughout
embryogenesis. During gastrulation groups of cells move from the surface and come to rest at consistent internal locations. This movement is directed, not random. Differences in migration tendencies seem to be inherent in cells from different regions of the embryo. In some instances, groups of cells isolated from different regions of the gastrula undergo movements they would have accomplished in situ. That cellular movement during gastrulation is active, not passive, is also demonstrated by bottle cells.

118
Q
  1. What tissues are derived from the hypoblast?
A

• Extraembryonic endoderm, yolk sac endoderm

119
Q

. What tissues are derived from the epiblast?

A

• Ectoderm, Mesoderm, Endoderm

120
Q

When does gastrulation occur in humans?

A

• Occurs at the end of the second week of gestation (into epiblast + hypoblast)

121
Q
  1. Describe the results of grafting a second dorsal lip to the blastocoel of an early amphibian embryo.
A

• Induces a secondary embryo to form

122
Q
  1. What factor represents the first sign of asymmetry in the mammalian embryo?
A

• Involves the beating of cilia around the primitive node: TGF-B
o Nodal + Lefty-1

123
Q
  1. Name the three classical markers of the organizer region in many vertebrates.
A
  • Chordin
  • Gossecoid
  • Fox-2
124
Q
  1. Which signal molecule is expressed by the isthmic organizer?
A
  • Signaling center boundary between Otx-2 and Gbx-2

* Releases Wnt-1 anteriorly (En-1) and FGF-8 (En-2) posteriorly

125
Q

Describe the results to neurulation that would be caused by the absence of the planar cell polarity pathway.

A

Neural folds remain far apart and neural tube closure is absent.

Embryo (3 decks)

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