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EMBRYO EXAM 1 > The review > Flashcards

The review Flashcards

1
Q

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

A

Endodermal yolk sac

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2
Q

Define morphogenesis

A

generation of form or assumption of shape

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3
Q

Define differentiation

A

complex changes involved in progressive specialization of structure

can result in the formation of luxury molecules

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4
Q

Define ontogeny

A

all developmental processes from contraception to death

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5
Q

Define determination

A

process by which a cell or part of an embryo becomes restricted to a pathway

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6
Q

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

A

Prophase- zygotene

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7
Q

At what stage of meiosis I does crossing-over occur?

A

Pachytene and diplotene

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8
Q

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

A

Monosomy-1(haploid), trisomy-3, poly-more than two sets of chromosomes

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9
Q

During oogenesis, when does the first meiotic arrest occur?

A

In the early embryo

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10
Q

During oogenesis, when does the second meiotic arrest occur?

A

Before or after birth; diplotene phase is the second meiotic arrest

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11
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 that is not surrounded by follicle cells –No follicle
  • 1 chromosome
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12
Q

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

A

Progesterone? L2 S5

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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 germ cells are present at embryonic midterm
  • 2 million at birth
  • Decline pretty consistently from there
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14
Q

What is the fate of most of the female germ cells?

A

Atretic- degeneration of follicle

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15
Q

Describe the oocyte at the time of ovulation.

A

Arrested at metaphase 2

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16
Q

What is the role of LH in resumption of meiosis? How is this related to MPF?

A
  • Meiosis resumes and is arrested at metaphase 2

- cAMP decreases and activates MPF (matruration promoting factor) which leads to meiotic arrest

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17
Q

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

A
  • Theca externa-angiogenesis factor

- Interna- LH receptors, secrete testosterone

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18
Q

What components of the Graafian follicle form the corpus luteum?

A

Follicle after the ovum YEETs

residual theca and granulosa

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19
Q

What is the function of aromatase?

A

Converts testosterone into 17beta estradiol

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20
Q

What hormone stimulates formation of LH receptors on granulosa cells?

A

Estrogen

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21
Q

What is the principal energy source for ejaculated spermatozoa?

A

Fructose

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22
Q

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

A

Upper vagina

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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
  • Spermatids (N) x 4
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24
Q

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

A

Forming sperm on one side and spermatogonia on the other

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25
Q

Describe the functions of Sertoli cells and cells of Leydig.

A
  1. Cells of Leydig: produce testosterone
  2. Sertoli cells: physical support and maintenance, spermatogenesis, secrete estrogen, blood testis barrier, phagocytize residual bodies
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26
Q

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

A
  • LH: stimulates Leydig cells to synthesize testosterone from cholesterol
  • FSH: stimulates testosterone to estrogen -Testosterone is taken to the secondary sexual tissues
  • Inhibin increases sperm count
  • Estrogen: help to form spermatozoa
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27
Q

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

A

Maturation; changes in the sperm head (acrosomal)

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28
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.

  1. FSH
  2. LH
  3. Estradiol
  4. Progesterone
A
  1. FSH-growth of ovarian follicle
  2. LH-surge triggers ovulation
  3. Estradiol- proliferation phase of the endometrium; drop leads to menstrual bleeding 4.Progesterone- drop leads to bleeding
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29
Q

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

A

LH with a slight rise in FSH

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30
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
  • Luteal phase the follicle will secrete estrogen and progesterone
  • **If NOT fertilized
  • -No more progesterone and estradiol, inhibin inhibits FSH which causes regression of corpus luteum
  • **IF fertilized
  • Chorioic gonadotropin from future placenta come in, granulosa lutein cells replace theta lutein cells, corpus luteum keeps doing her thing for months
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31
Q

What is the role of inhibin in relation to the ovarian cycle?

A

Stops gonadotropins, FSH, and regresses corpus luteum

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32
Q

What is the most likely site of fertilization?

A

Ampulla

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33
Q

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

A
  • Fertilization age: from the time of fertilization

- Menstrual age: from the last menstrual period; two weeks later than fertilization

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34
Q

Describe capacitation and explain where it occurs.

A

Sperm binds to egg, acrosomal reaction

35
Q

What is the major action of hyaluronidase?

A

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

36
Q

Define “zygote.”

A

Diploid cell from the fusion of two haploid gametes, a fertilized ovum

37
Q

With regard to fertilization, what are the characteristics of the fast block to polyspermy?

A

Prevents polyspermy and allows for slow block establishment

38
Q

With regard to fertilization, what are the characteristics of the slow block to polyspermy?

A

Release of polysaccharides from cortical granules, which go in between plasmalemma and zona pellucida, become hydrated and swell

39
Q

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

A
  • ZP3- stimulates acrosomal reaction
  • Phospholipase C zeta- produced by the sperm to increase the calcium release in the egg which blocks polyspermy, increases egg respiration, and increases the pH
40
Q

What ion initiates metabolic activation of the egg? What are the results of this activation?

A

Calcium; blocks polyspermy, increases the respiration of the egg, and increases the pH

41
Q

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

A

Required to permit cleavage to the 2-cell stage

42
Q

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

A

Cdx-2, Oct-4, Nanog, Sox2

43
Q

Describe the general structure of the blastocyst, including the different components.

A

Surrounded by the zona pellucida, has two cells: outer layer=trophoblast which forms the extraembryonic structures like the placenta. Inner mass of cells+ inner cell mass which is the embryo and a lil bit

44
Q

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

A
  • Nanog become epiblast cells

- Gata 6 become hypoblast cells which are induced by FGF-4

45
Q

At what point in development does most transcription via the embryonic genome begin to occur?

A

4 cell stage

46
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
  • Demethylation occurs shortly after fertilization until the early morula
  • Methylation levels fall after the primordial germ cells enter the genital ridges
47
Q

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

A

Polyploidy; abnl chromosome number

48
Q

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

A
  1. Inside-out hypothesis: Fate of the blastomere is determined by the position within the embryo, not intrinsic properties
  2. Cell polarity model: depends on plane of cell division
49
Q

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

A
  • Cdx-2: trophoblast cell differentiation
  • Oct-4: required to proceed to the 2-cell stage; maintain the undifferentiated state; without differentiates into the trophoblast
  • Nanog: maintains integrity of inner cell mass; without it differentiates into endoderm
  • Sox-2: 8 cell stage, control regulation of genes
50
Q

Compare Prader-Willi and Angelman syndromes and relate to genomic imprinting.

A

Prader Willi is due to a deletion in the paternal allele and Angelman is due to a maternal allele; both on chromosome 15

51
Q

When does X-inactivation take place in humans?

A

First few weeks of development

52
Q

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

A

XO- Turner
XXY/XXYY/XXXY/XXXXY- Kleinfelter
XXX- triploX
XXX+: Poly X female

53
Q

When does X-inactivation take place in humans?

A

First few weeks of development

54
Q

What role does Xist play in X-inactivation?

A

Produces an RNA molecule that coats the X chromosome and induces inactivation; removes acetyl groups from histones, methylates histones, alteration of histone composition

55
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

Females will have 1 inactivated X and it would be V bad if the male has one

-provides equal expression of X-chromosome products in both males and females

56
Q

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

A

Expanded blastocyst; embryonic pole

Syncytiotrophoblast

57
Q

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

A

Splitting of the inner cell mass of a blastocyst of the two embryos enclosed in a common trophoblast

58
Q

List functions of the zona pellucida.

A

Surround the embryo until it reaches the uterus

59
Q

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

A
  • Cellular cytotrophoblast (closest to inner cell mass)

- Multinucleated syncytiotrophoblast (closest to the endometrium)

60
Q

Describe the process of implantation.

A
  1. Attachment of blastocyst
  2. Penetration of the uterine epithelium
  3. Invasion of the tissues underlying the epithelium
  4. Erosion of the maternal vascular supply
61
Q

What is the most common site for ectopic pregnancy?

A

Ampulla

62
Q

Describe the decidual reaction and its function(s).

A

Response of the endometrial stroma cells to the invading blastocyst; without it the blastocyst may eat all the way through the wall. INSTEAD the reaction encapsulates the embryo and also releases IL-2 so that the mother’s body does not attack the fetus

63
Q

Which signaling pathway is often involved in lateral inhibition?

A

Delta notch

64
Q

Which signaling pathway is often utilized by TGF-β?

A

Receptor kinase pathway

65
Q

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

A
  • Loss of function: result in posterior to anterior transformations
  • Gain of function: result in anterior to posterior transformations
66
Q

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

A
  1. Egg polarity genes include genes that establish the dorsal-ventral axis, and the anterior-posterior axis
    - –Transcribed into mRNA’s in the ovary and the eggs are translated into proteins after fertilization
  2. Gap genes-gene segmentation; delete adjacent segments
  3. Pair-rule genes- segmentation genes, delete the same part of pattern in every other segment
  4. Segment-polarity genes- affect the polarity of segment
  5. Homeotic genes- determine the identity of individual segments; encode the segment specific characteristics; expressed after fertilization-contain homeobox
67
Q

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

A

Hedgehog

68
Q

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

A
  1. Dorsal-from dorsal gene and is expressed in the ovary; becomes concentrated on the ventral surface
  2. Cactus- from the cactus gene and binds to the dorsal protein to trap it in the cytoplasm
  3. Toll protein- produced by the toll gene in the ovary and leads to the degradation of cactus which lets dorsal protein move into ventral cells
69
Q

Describe the MiRNA pathway and its components.

A
  1. Has 2 groups, Piwi-interacting RNA’s (piRNA) that act during gametogenesis and endo-siRNAs that are expressed throughout development
  2. Dicer cleaves the miRNA and the AGO loading protein goes and loads it into the target (THESE ARE IN RED IN LECTURE)
70
Q

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

A
  • Bicoid, nanos, hunchback
  • Bicoid regulates the anterior structures and stimulates hunchback
  • Nanos genes are responsible for the posterior structures and inhibits hunchback
71
Q

Zinc-finger transcription factors are associated with which gene family?

A

Sox genes (including SRY) and WT1 important for the kidney

72
Q

What is a morphogen?

A

A protein that varies in concentration and causes different developmental responses based on concentration gradients

73
Q

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

A

Bottle cell is the primitive streak?? Which marks the start of gastrulation and starts the formation of the three germ layers

74
Q

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

A

Nodal and Wnt3?

75
Q

What tissues are derived from the hypoblast?

A

Extraembryonic structures

76
Q

What tissues are derived from the epiblast?

A

Amniotic endoderm and the embryo

77
Q

When does gastrulation occur in humans?

A

End of the second week of gestation

78
Q

What factor represents the first sign of asymmetry in the mammalian embryo?

A

Beating of cilia around the primitive node, which forms a directional current and expression of TGF-beta molecules; nodal and lefty

additional factors: Shh, retinoid acid, FGF-8

79
Q

Name the three classical markers of the organizer region in many vertebrates.

A

Chordin, Gossecoid, Fox-2

80
Q

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

A

PCP pathways are important in folding the neural plate into the neural tube; without it, the neural folds would remain far apart and the neural tube closure is absent

81
Q

Which signal molecule is expressed by the isthmic organizer?

A

Wnt-1 anteriorly and FGF-8 posteriorly

82
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

83
Q

What are the two arrests that occur in the oocyte?

A

1: Diplotene of prophase 1
2: metaphase 2

EMBRYO EXAM 1 (2 decks)

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