To save content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about saving content to .
To save content items to your Kindle, first ensure firstname.lastname@example.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
This chapter reviews molecular mechanisms that control germline formation through a complex cascade of gene activation. In mammals, primordial germ cells (PGCs) are derived from the proximal epiblast during early embryogenesis. Interestingly, although both FRAGILIS and STELLA are differentially expressed in PGCs, neither appears to be essential for PGC specification. In general, migration of PGCs from primitive streak to genital ridges is believed to be governed by chemotactic cytokines, cell surface receptors, and cell adhesion factors. Until the colonization of the genital ridges, XX and XY PGCs are indistinguishable in terms of morphology and behavior. Mammalian male sex determination is initiated by sex-determining region Y (SRY) expression in XY genital ridges, which triggers Sertoli cell differentiation in supporting cell precursors. Germ-cell colonization of the gonads is followed by sex determination. Expression of sex-specific genes in somatic tissues initiates molecular events that lead to testis or ovary development.