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ANAT 381 Experimental Embryology > Making germ cells > Flashcards

Making germ cells Flashcards

1
Q

What are the two fates of primordial germ cells?

A

Oogonia -> oocytes
Spermatogonia -> spermatocytes

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2
Q

Germ cells that are fundamentally different from somatic cells live a(n)
a) Infinite life
b) Finite life

A

a) Infinite life

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3
Q

Germ cells that are not fundamentally different from somatic cells live a(n)
a) Infinite life
b) Finite life

A

b) Finite life

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4
Q

In nematodes, certain regions of chromatin are degraded in ____________ cells and all chromatin is retained in _____________ cells

A

Somatic; germ

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5
Q

In Drosophila, pole cells segregated at _____________ end of embryo contain ____________ cell determinants

A

Posterior; germ

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6
Q

In C. elegans, aggregates of mitochondria, RNA and protein in egg become segregated to _____________ cells

A

Germ

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7
Q

What does embryo biopsy search for?

A

The presence of mutations in the embryo by genetic analysis of one of the germ cells

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8
Q

What are the key events of differentiation of the PGCs?

A

PGC determination, sex determination, PGC migration and gametogenesis

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9
Q

Which cells of the embryo of a mouse form the embryo?

A

Posterior and anterior epiblast

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10
Q

How many anatomical positions of newly specified PGCs can be found in mouse and in humans?

A

Mouse: one
Humans: two

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11
Q

PGCs arise from the _____________ epiblast

A

Posterior

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12
Q

What experiment was done to determine that PGCs came from the posterior epiblast?

A

Cells from the distal tip of epiblast were transplanted to the posterior epiblast
Normally, they would give rise to neuroectoderm cells
Yet, they differentiated into PGCs

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13
Q

What cell signaling pathways are important in PGC specification?

A

Wnt and TGFb pathways

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14
Q

What is the mechanism of Wnt signaling?

A

Wnt binds to its receptor
This activates b-Cat which translocate to the nucleus and activates the transcription of genes
In the absence of Wnt, b-Cat is bound up and degraded in the cytoplasm

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15
Q

What is the mechanism of TGFb signaling?

A

TGFb and BMP bind to their receptors
SMAD proteins are activated and translocated to the nucleus to activate gene transcription

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16
Q

BMP is secreted by which cell type?

A

Extraembryonic ectoderm cells

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17
Q

What are some roles of the genes responsible for specification of PGCs?

A

DNA-binding domain regulator and TM protein/viral entry

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18
Q

DNA methylation modifies which nucleotide within the chromatin?

A

Cytosine

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19
Q

Which enzyme mediates DNA methylation?

A

DNMT1

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20
Q

DNA methylation can be transmitted ____________ DNA replication and therefore is _____________ during cell proliferation

A

After; heritable

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21
Q

DNA methylation of _________ ____________ is linked to the repression of gene expression

A

Gene promoters

22
Q

When does the DNA of PGCs become demethylated?

A

When they are specified

23
Q

What is totipotency?

A

Ability to acquire a pattern of any cell type

24
Q

DNA demethylation may help give germ cells ________________

A

Totipotency

25
Q

SRY was discovered in the _____________ chromosomes of __________

A

Y; males

26
Q

XX mice carrying SRY develop as _____________

A

Males

27
Q

How was the male-determining gene located in humans?

A

Translocate the region of Y chromosome to the X chromosome and observe through DNA sequencing where the region of Y-chr was found in X-chr of phenotypic males having XX genotype

28
Q

Which domain in SRY gene binds to DNA?

A

HMG domain

29
Q

What is the role of SRY in somatic cells of the genital ridge when it is expressed?

A

Production of testosterone from differentiation of Sertoli cells and Leydig cells

30
Q

What is the role of SRY in somatic cells of the genital ridge when it is not expressed?

A

Secondary female sexual differentiation from the differentiation of pre-granulosa cells and pre-theca cells

31
Q

SRY turns on the expression of _____________ gene in the genital ridge

A

Sox9

32
Q

Does Sox9 expression require SRY in other tissues?

A

No

33
Q

Sox9 gene expression leads to ____________ sex determination

A

Male

34
Q

Which other gene is required for male sex determination?

A

Fgf9

35
Q

Which genes are required for female sex determination?

A

Wnt4 and Rspo1

36
Q

Wnt4 and Rspo1 mutations lead to _____________

A

Partial female-to-male sex reversal

37
Q

What proteins are required for female sex determination?

A

b-Cat/Lef1 and FoxL2

38
Q

Germ cells in ____________ maintain mitotic arrest until puberty, while germ cells in ___________ enter meiosis

A

Males; females

39
Q

Which gene is correlated with the entry into meiosis?

A

Stra8 turned on by retinoic acid

40
Q

How does RA activate the expression of Stra8?

A

Retinol binds to Stra6 and is metabolized to retinoic acid by retinol dehydrogenase and retinal dehydrogenase
CRABP carries RA to the nucleus where it activates the expression of Stra8

41
Q

Why don’t XY germ cells respond to environmental RA?

A

Cyp26b1 degrades RA in embryonic male gonads

42
Q

True or false: Mice lacking Cyp26b1 will enter meiosis

A

True

43
Q

Which cells in male gonads block RA from acting?

A

Sertoli cells

44
Q

Gonochorism occurs when individuals reproduce as one ___________ throughout their lifetime

A

Sex

45
Q

Protogyny occurs when individuals first reproduce as _____________, change sex once with increasing size/age and then reproduce as ____________

A

Females; males

46
Q

Protoandry occurs when individuals first reproduce as _____________, change sex once with increasing sex/size and then reproduce as _______________

A

Males; females

47
Q

Bidirectional sex determination is when individuals can change sex more than once, in either ______________, throughout their lifespan

A

Direction

48
Q

Simultaneous sex determination is when individuals produce gametes of both _____________ at the same ____________

A

Sexes; time

49
Q

Mullerian duct gives rise to _____________ gonads and Wolffian duct gives rise to ____________ gonads

A

Female; male

50
Q

What triggers Mullerian duct regression?

A

AMH (Anti-Mullerian hormone)

51
Q

What is the phenotype of individuals with 5-a-reductase lacking the ability to convert testosterone to di-hydrotestosterone?

A

Females at birth, male external genitalia form at puberty, some individuals produce functional sperm

ANAT 381 Experimental Embryology (24 decks)

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