Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

DEVELOPMENTAL > week 12 > Flashcards

week 12 Flashcards

1
Q

what is gametogenesis?

A

the formation of germ cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

gametogenesis includes which 5 processes?

A

the formation of the germ plasm and the determination of the PGCs

the migration of the PGCs into the developing gonads

the process of meiosis and the modifications of the PGCs into the developing gonads

the process of meiosis and the modifications of meiosis for forming sperm and egg

the differentiation of the sperm and egg

the hormonal control of gamete maturation and ovulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

there are 2 methods of PGC determination

A

PGCs can be specified by cytoplasmic determinants in the egg: the germ plasm

PGCs can be specified by interactions among neighbouring cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Germ cell determination by cytoplasmic determinants in nematodes (worms).
What happens to the chromosomes in nematodes?

A

chromosomes fragment into dozens of pieces in somatic cells. the germ plasm prevents fragmentation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

In the nematode c.elegans the germ line precursor cell is the ____

A

P4 blastomere

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

P-granules become localised to the P4 blastomere. What are these?

A

these are ribonucleoprotein complexes that specify the germ cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what do the P-granule proteins contain?

A

several transcriptional inhibitors and RNA binding proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

why dont germ line cells turn into somatic cells?

A

expression of somatic genes is inhibited in the P4 blastomere preventing the cell to differentiate into a somatic cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

In Drosophila PGCs form how?

A

as a group of pole cells at the posterior pole of the blastoderm. Nuclei migrate to the posterior area and become surrounded by the pole plasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

The __ ___ specifies the germ cells and inhibits somatic gene expression in these cells in Drosophila

A

pole plasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Drosophila - the mRNA of the maternal gene germ cell-less (gcl) is localised to the posterior pole. What is the protein?

A

the protein is a component of the pole plasm and is essential for pole cell production

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what are required in drosophila for localising mRNAs and proteins to the posterior pole?

A

posterior group determinants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is Oskar and Nanos?

A

Oskar functions by localising proteins and mRNAs necessary for germ cell formation.

Ectopic Oskar localisation results in ectopic germ cells.

Nanos is localised by Oskar.

Nanos prevents the pole cells from developing into somatic cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

In the unfertilised frog egg the germ plasm consists of what?

A

several islands bound to the yolk. these islands fuse together and migrate to the vegetal pole after fertilisation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the function of the germ plasm?

A

inhibition of transcription and translation of somatic genes

induction of germ cell development

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How is the germ cell determined in mammals?

A

no germ plasm

BMP signals from the extra embryonic ectoderm induce neighbouring embryonic cells to become germ cell precursors. During gastrulation the germ cell precursors become located in the posterior part

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

broadly how do germ cells migrate in drosophila?

A

germ cells form as a group of pole cells. Pole cells attach to endoderm (posterior midgut rudiment) and are displaced into the pmg by the gastrulation movements (passive movement)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Germ cell migration in Drosophila. :

Gut ____ triggers the pole cells to migrate (active movement) through the blind end of the ___

Pole cells attach to mesoderm. The ___ protein directs migration from endoderm to mesoderm by ____.

Pole cells align with gonadal mesoderm. The proteins ___ and ___ (produced by the gonads) attract the pole cells

Pole cells and gonad precursor cells are divided into two streams. The ____ protein is involved in the separation

The ____ coalesce around the germ cells, the germ cells can now divide and mature into gametes

A 
endoderm 
pmg
Wunen
Repulsion
Columbus
Hedgehog
Wunen
gonads
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Gonadal maturation occurs during ____

A

metamorphosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What happens to the PGCs at metamorphosis?

A

the PGCs in the anterior region of the gonad become stem cells. Asymmetric division occurs - stem cell + cytoblast

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How is the egg chamber formed?

A

The cytoblasts are interconnected by the ring canals (cytoplasmic bridges). One of these cells becomes the oocyte (egg), the remaining 15 cells become nurse cells. The nurse cells produce RNAs and proteins that are transported into the egg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How does the germ cell migrate in the zebra fish?

A

the germ plasm accumulates along the cleavage planes during the first two divisions. There are four clusters of germ cells in the early zebrafish embryo. The PGCs follow a gradient of the Sdf1 protein. Sdf1 is secreted by the developing gonads and the PGCs express the sdf1 receptor CXCR4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Germ cell migration in mammals.
PGCs move from the posterior region of the primitive streak into the ______.

PGCs then exit the gut and migrate towards the genital ridge (_____)

migration occurs along the __ and probably involves soluble proteins like Sdf1 in the zebrafish.

A

hindgut (endoderm)
gonade primordium
ECM

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

In mammals the PGCs proliferate during migration (from 10 to 5000). Proliferation depends on what?

A

FGF7 and the stem cell factor SCF

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

The maturation of germ cells occurs when?

A

the germ cells reduce their chromosomes from the diploid to the haploid condition

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

meiosis differs from mitosis in that? (2)

A

homologous chromosomes pair together and combine genetic material

meiotic cells undergo two cell divisions without an intervening period of DNA replication

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

In higher eukaryotes all cells are diploid except?

A

the egg and sperm are haploid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Spermatogenesis in mammals

A

PGCs become incorporated in to the sex chords in the testis. The sex cords then hollow out and form the seminiferous tubules. The epithelium of the tubules differentiates into the sertoli cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what do the sertoli cells do?

A

protect and nourish

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

the initiation of spermatogenesis occurs at puberty and depends on high concentrations of ______ in the PGCs

A

BMP8b

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is the transition between spermatogonia and spermatocytes induced by? and where is this secreted?

A

GDNF

sertoli cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

As germ cells mature they progress where?

A

towards the lumen of the seminiferous tubule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Why does oogenesis differ from spermatogenesis?

A

the sperm are essentially motile nuclei, in contrast, the egg contains all the material needed to initiate development. Therefore in addition to forming a haploid nucleus, oogenesis also builds up a store of cytoplasmic enzymes, mRNAs, organelles and metabolic substrates

34
Q

Oocytes continuously die and only about 400 mature during a womans life time, explain more

A

between the 2 and 7 month of development about 7 million germ cells are formed. Most of the oogonia die before birth. The remaining oogonia become arrested in the first meiotic prophase. Only about 12 years later at puberty is meiosis completed

35
Q

In oogenic meiosis how is the cytoplasm distributed?

A

it is unequally distributed between the daughter cells

36
Q

oocyte maturation is arrested in the first meiotic prophase and actiavted by what?

A

progesterone

37
Q

In some animal species meiosis is greatly modified. How so?

A

The oocyte remains diploid and therefore need not be fertilised to develop. this is called parthenogenesis

38
Q

What are the primordial germ cells?

A

the precursors of the gametes - the sperm and egg

39
Q

The PGCs form outside the ___ and migrate to the ___ during development

A

gonads

40
Q

Until the 20th century it was believed that sex was determined by the __

A

environment

temperature and nutrition was thought to be important.

only after the rediscovery of Mendels work in 1900 and the discovery of the sex chromosome was a correlation made between sex chromosomes and sex determination

41
Q

What is chromosomal sex determination?

A

In mammals the presence of either a second X chromosome or a Y chromosome determines if hte embryo is to be female or male

in birds the situation is reversed males are ZZ and females heterozygote ZW

42
Q

What is sex determination like in insects?

A

the Y chromosome plays no role in sex determination, instead the ratio of sex chromosomes to autosomes determines the sex

43
Q

In mammals what are the 2 types of sex determination?

A

primary and secondary.

Primary - determination of the gonads, this is determined by the sex chromosomes.

Secondary - determines the phenotype outside the gonads e.g. musculature, body size etc

44
Q

Mammalian chromosomal sex determination results in what sort of sex ratio?

A

approximately equal

45
Q

The mammalian gonads develop through a _____ stage. explain

A

bipotential or indifferent

genital ridge epithelium proliferates, germ cells migrate into gonads, the paired gonadal rudiments develop next to the kidneys

46
Q

What is gonadal development like in males and females?

A

in males the sertoli cells in the testis cord secrete the anti mullerian hormone which blocks the development of the female ducts. Leydig cells produce testosterone, the Wolfifan duct is maintained.

In females each individual germ cell is surrounded by somatic cells. the mullerian duct is maintained. Due to the lack of testosterone the Wolffian duct degenerates. The mullerian duct develops into the oviduce, uterus etc

47
Q

what is the Wolffian duct?

A

tube through which the sperm pass into the urethra

48
Q

Why are clinical infertility studies useful in finding out which gene determines sex?

A

because the phenotype of mutations in sex determining genes is often sterility

49
Q

Which gene determines sex in humans?

A

in humans the major gene for testis determination is located on the short arm of the Y chromosome.
This gene is called SRY and is a transcription factor.

50
Q

what does SRY stand for?

A

sex determining region of the Y chromosome

51
Q

Where is SRY expressed?

A

SRY is expressed in the somatic cells of the bipotential mouse gonads of XY mice immediately before these cells differentiate into sertoli cells.

52
Q

What provides evidence that SRY controls male development?

A

XX mice which are transgenic for SRY develop into males in experiments

53
Q

What other gene is also required for sex determination?

A

SOX9

54
Q

what is SOX9

A

an autosomal gene that can induce testis formation.

55
Q

what is evidence that SOX9 is implicated in sex determination?

A

XX humans who have an extra copy of SOX9 develop into males.

Knocking out the SOX( gene in the gonads of XY mice causes complete sexreversal.

56
Q

SOX9 binds to the promotor of the gene for the ____hormone

A

anti mullerian

57
Q

Which growth factor may be regulated by SRY or SOX9?

what evidence?

A

fibroblast growth factor 9

When Fgf9 is knocked out in mice, almost all mice become females.

Fgf9 causes proliferation of the sertoli precursors and stimulates their differentiation

Fgf9 is also required for bringing mesonepheric cells into the gonads

58
Q

what is the role of the mesonepheric cells?

A

important in forming the testis cords

59
Q

what evidence shows that the mesonepheric cells are important in forming the testis cords?

A

the gonad rudiment was removed from XX mice and combined with the XX or XY mesonephros of blue mice = no migration

the gonad rudiment was removed from XX mice and incubated in Fgf9 and then combined with mesonephric cells from blue mice = migration

60
Q

Are there genes that produce the ovary?

A

at present there is no known gene that is ovary specific

61
Q

which gene has been suggested to produce the ovary?

A

the gene DAX1 which is located on the X chromosome seems to antagonise the expression of the testis forming gene SRY.

2 copies of DAX1 supress SRY expression, male gonads do not develop.

62
Q

what is secondary sex determination (more detail)

A

the development of the female and male phenotypes in response to hormones secreted by the ovaries and testis

63
Q

what are the 2 phases of secondary sex determination?

A

within the embryo

at puberty

64
Q

the formation of the male phenotype involves the secretion of 2 testicular hormones?

A

AMH - anti mullerian hormone

steroid hormone

65
Q

where is the AMH made and what does it do?

A

sertoli cells

degeneration of the mullerian duct

66
Q

where is the steroid hormone secreted? what do?

A

leydig cells

testosterone causes the Wolffian duct to differentiate into the internal and external male genitals

67
Q

Why do people with androgen insensitivity syndrome develop as sterile women?

A

these XY individuals produce testosterone and AMH.
AMH causes the female mullerian duct to degenerate.

but they lack the receptor protein for testosterone and can therefore not respond to the testosterone made by the testis - no male reproductive organs

but they can respond to the estrogen made by adrenal glands - overall female appearance

despite their female appearance these women do not develop a uterus and oviducts because the mullerian duct degenerates

68
Q

what is female pseudohermaphroditism?

A

the gonadal sex is female but the person is outwardly male

69
Q

what causes female pseudohermaphroditism?

A

the most common cause is the overproduction of androgens (male hormones) in the ovary or in the adrenal gland due to the absence of an enzyme that metabolises cortisol steroids which results in accumulation of testosterone like steroids. the embryo is masculinised.

70
Q

what are the sex differences in the brain that can be observed even before the gonads form?

A

XX embryonic rat brains have more epinephrin-expressing neurons than XY rat brains.

The SRY gene is not only expressed in the embryonic testis but also in the male embryonic and adult brain

71
Q

In finches there are sex differences in the brain, what are they?

A

in male finches large regions of the brain are devoted to producing songs. female finches do not sing but if hormones are added experimentally singing can be induced in females.

72
Q

how is sex determined in Drosophila melanogaster?

A

the y chromosome is not involved in determining sex. the y chromosome is important in sperm cell differentiation. the fruit flys sex is determined by a balance of female determinants on the x chromosomes to male determinants on the autosomes.

73
Q

What are gynandromorhps?

A

half male and half female. there are no sex hormones in insects, each cell makes its own sexual decision. the loss of an x chromosome from one embryonic nucleus results in gynandromorphs in insects.

74
Q

what is the sex determination cascade?

A

comes down to what type of mRNA is processed from the dsx transcript. If the ratio is 1 (2X:2A), Sxl is activated and causes the tra transcript to be spliced in female specific manner. Tra then interacts with tra2 to cause the dsx transcript to be spliced in a female specific manner. In males the double sex transcript is processed in a default manner to make the male specific message.

75
Q

Male courtship behaviour is regulated by which protein in Drosophila?

A

Fruitless protein

76
Q

What happens when fruitless is misexpressed in female flies?

A

they perform the entire male courtship ritual. try to mate with other female

77
Q

Temperature dependent sex determination - alligator, red turtle, green turtle?

A

alligator = females at low temperature

red turtle = females at hot and cold temperatures

green turtle = females at hot temperature

78
Q

How does temperature regulate sex determination? theory 1

A

cell proliferation and maleness

rapid cell divisions are required for testis formation (rapid production of sertoli cells). Higher temperatures could increase cell proliferation and direct gonadogenesis in the male direction

79
Q

how does the temperature regulate sex determination? theory 2

A

hormones determine the sex

the enzyme aromatase which converts testosterone into estrogen may be critical in temperature dependent sex determination. If the aromatase level is low male offspring are produced. There is a correlation under natural conditions, male producing temperatures = low aromatase level

80
Q

Pollutants introduced into the environment by humans can act like estrogens?

A

PCBs can reverse the sex of turtles raised at male temperatures. this knowledge is important for protecting endangered species.

DEVELOPMENTAL (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions