Gametogenesis Flashcards
What is the default sex in gametogenesis?
Female.
What is the Sry?
The test-determining factor.
What happens if Sry is absent?
The sex is female.
What does the Sry activate?
Sox9.
What is the result of Sry being present?
It induces sex cords that form seminiferous tubules.
What do seminiferous tubules contain?
Sertoli cells and leydig cells.
What are sertoli cells?
They are cells that secrete anti-Mullerian hormone to prevent female development.
What are leydig cells?
Cells that secrete testosterone to promote development of the male reproductive system.
What is spermatogenesis?
The process from which haploid spermatozoa develop from germ cells in the seminiferous tubules of the testes.
When does spermatogenesis initiate?
Puberty.
When does differentiation of spermatozoa occur?
When the threshold of BMP8b is reached.
What else happens in mammalian spermatogenesis?
There is anchoring to sertoli cells via N-cadherin.
What is the first committed stem cell type in mammalian spermatogenesis?
The intermediate spermatogonia.
What is the last mitotic division in mammalian spermatogenesis?
The change from type B spermatogonia to primary spermatocytes.
What is differentiation favoured by?
Low concentration GDNF and high concentration SCF.
What produces GDNF and SCF?
Sertoli cells.
What happens in meiosis?
Secondary spermatocytes form from primary spermatocytes.
What happens in spermiogenesis?
Residual bodies are formed from spermatids.
What is spermiogenesis?
Post-meiotic generation of sperm.
What happens in post-meiotic generation of sperm?
A round spermatid develops to a testicular sperm.
What is the starting point of mammalian spermiogenesis?
It begins with a non-flaggelar haploid round spermatid.
What happens with the golgi apparatus in spermiogenesis?
It forms the acrosome which covers part of the nucleus. On the basement side, the flagella sticks into the lumen.
What are histones replaced in during spermiogenesis?
Protamine.
What happens when histones are replaced with protamine?
There is non-nucleosomal chromatin and transcription almost completely shuts down.
What is the structure of chromatin at the start of spermiogenesis?
It is nucleosomal.
What are histones replaced with in spermatids in sperm chromatin formation?
Transition proteins - tnp1 and tnp2 in round spermatids.
What is established in spermiogenesis?
Paternal imprints.
What does spermiogenesis result in?
Non-nucleosomal chromatin.
What happens to transcription during spermiogenesis?
It almost completely shuts down.
What is significant about chromatin at the beginning of spermiogenesis?
It is nucleosomal.
What are histones replaced by in spermiogenesis?
Transition proteins TNp1 and Tnp2 in round spermatids.
What is the distinction between round spermatids and elongating spermatids?
Round spermatids contain transition proteins that have replaced histones, whereas elongating spermatids
How long does spermatogenesis take in humans?
65 days.
What happens to cells, in terms of distance from the basal lamina, during differentiation?
They move further away.
What transcription factor is essential for spermatogenesis?
TAF4b testis-specific TBP associated transcription factor.
What is the epididymis?
A duct behind the testis where sperm passes to the vas deferens.
What needs to happen to testicular sperm?
As testicular sperm are not capable of fertilisation (and lack forward motility), this ability needs to be acquired during epidymidal transit.
What happens during epididymidal transit?
They undergo extensive membrane changes.
What is oogenesis?
Differentiation of the female gamete, the oocyte.
What are the two types of oogenesis?
Continuous and finite oogenesis.
What is continuous oogenesis?
Ooogenesis from self-sustaining population of mitotically dividing oogonia. It is similar to spermatogonia and occurs in fish, amphibia, sea urchins and insects.
What is finite oogenesis?
When it is generated in the embryo and arrested until small numbers resume meiosis. This occurs in birds, mammals and reptiles - only a few eggs are generated until they are released or fertilised.
Where does oogenesis occur in mammals?
It occurs in the ovaries and is associated with granulosa cells that become cumulus cells.
What are granulosa cells?
A somatic cell of the sex cord closely associated with the developing female gamete.
What is the purpose of granulosa cells?
They provide nutrition and support maturation.
What are some of the hormones that are involved in oogenesis?
Follicle stimulating hormone and luteinizing hormone.
What produces follicle stimulating hormone (FSH)?
The anterior pituatory gland.
What is the purpose of follicle stimulating hormone?
It stimulates the growth of ovarian follicles.
What is ovulation stimulated by?
A surge in leteinizing hormone.
What is luteinizing hormone produced by?
The anterior pituatory gland.
What is the structure of FSH?
It is an alpha/beta subunit heterodimer.
What is the structure of leutinizing hormone?
It is an alpha/beta heterodimer. The alpha subunit is shared with FSH.
What is the zona pellucida?
A unique glycoprotein matrix surround the oocyte.
What happens if the zona pellucida is removed?
Infertility.
What proteins is the zona pellucida made up of in humans and mice?
3 proteins in mice and 4 in human - ZP1, ZP2, ZP3, (ZP4).
What are the glycoproteins linked to in the zona pellucida?
O and N.
When are the zona pellucida proteins synthesised?
Oocyte growth phase.
What is significant about the ZP2 in the zona pellucida?
It is a receptor for sperm binding.
When is meiosis resumed in the oocyte?
It resumes from prophase 1 (check this ?) arrest after follicle growth, which is stimulated by FSH.
What is GVBD?
Germinal vesicle breakdown.
When does GVBD occur?
The end of prophase 1 - diplotene.
What is the polar body a product of?
Asymmetric cytokinesis.
When were mouse spermatids produced in vitro?
March 2016. They started from embryonic stem cells.
What can spermatids produced in vitro be used for?
Injection into a naturally produced mii oocytes - 1.9-2.7% 2-cell embryos develop to healthy offspring.
When were oocytes produced in vitro?
October 2016.
How were oocytes produced in vitro?
iPS cells or ES cells.
