germ cells

Question 1

in humans, what is the period of embryonic organogenesis

Answer 1

3-8 weeks

Question 2

where do gametes arise from?

Answer 2

primordial germ cells

Question 3

primordial germ cells

Answer 3

PGCs lie at the posterior part of the embryo just outside of the developing embryo
PGCs migrate to the gonads + become the progenitor population for eggs and sperm

Question 4

P cells in C elegans

Answer 4

Early, asymmetrical divisions of the cell produces a P cell - inherited P granules through asymmetric division.
P granules bind P cell DNA and turns off all transcription to block differentiation + blocks translation in cytoplasm. Activates 10-20 genes promoting stem cell fate + causing P cell to undergo meiosis.

Question 5

Nanos

Answer 5

gene expressed by germ cells

blocks transcription

Question 6

mammalian primordial germ cells

Answer 6

1. PGCs arise from mesoendodermal extra-embryonic tissue and sit below future posterior hindgut (anus). remain in this position to protect themselves from signals causing differentiation during early embryogenesis.
2. at 8 weeks (when embryonic organogenesis ends), PGCs migrate into the embryo
3. PGCs attach to endoderm and migrate through the hindgut by following a fibronectin trail using their integrin receptors
4. genital ridges secrete a chemoattractant to guide PGCs to migrate laterally out of the midgut and into the genital ridges
5. genital ridges and PGCs communicate by reciprocal inductive interactions to form gonadal niche protecting PCGs in totipotent state + supporting meiotic dvisions + egg or sperm formation

Question 7

what is the Drosophila equivalent of germ cells?

Answer 7

pole cells

Question 8

what gene do pole cells express?

Answer 8

vasa

Question 9

what is the drosophila support cell in the ovary microenvironment?

Answer 9

stromal cap

Question 10

what are genital ridges

Answer 10

2 bilateral intermediate mesoderm structures

Question 11

Drosophila and PGCs

Answer 11

at gonads, PGCs proliferate throughout larval stage
during metamorphosis, PGCs differentiate into eggs or sperm (depends on whether the microenvironment is an ovaries or testes microenvironment)

Question 12

what is the drosophila support cell in the testes microenvironment?

Answer 12

hub cells

Question 13

where do genital ridges arise from?

Answer 13

Wolffian duct

Question 14

Stem Cell Factor

Answer 14

secreted by support cells travelling with migrating PGCs creating a microenvironment to maintain stem cell fate