Download Developmental Biology, 9e

BIOL 370 – Developmental Biology
Topic #19
The Germ Line: Additional Concepts
Lange
In addition to creating their own body tissues, an animal must also
develop what are called germ cells. These cells will provide the
material and instructions for the next generation of that organism.
In most of the organisms we have studied, there is a clear
separation of germ cells from body (somatic) cells, but in some
organisms the demarcation is not so obvious (from class…. the
fern and the flatworm are examples).
In those groups that have a separate germ and somatic region, we
can see two different methods of specification:
• Autonomous germ cell specification (fruit flies for example)
• Induced germ cell specification (mammals for example)
Pole plasm of Drosophila
Here, we see Pole Cells
(both A&B) associated
with Drosophila.
Localization of germ cell-less gene products in the posterior of the Drosophila egg and embryo
Gcl is an allele refered to as “germ cell less”. In these images, we see the effects
of this abnormal allele in the mutant form. The lack of the germ plasm
component necessary for the proper formation of 'pole cells', the germ cell
precursors in Drosophila results in poor/no formation of pole cells.
Photomicrograph of a section through a mouse teratocarcinoma, showing numerous differentiated
cell types
A teratocarcinoma refers to a germ cell
tumor that is a mixture of teratoma with
embryonal carcinoma. This is a kind of
mixed germ cell tumor.
Teratomas have
been reported to
contain hair, teeth,
bone and, very
rarely, more
complex organs or
processes such as
eyes, torso, hands,
feet, or other limbs.
Protocol for breeding mice whose genes are derived largely from tumor cells
This technique allows us to
study specific tumor producing
genes that can be specifically
expressed throughout the who
organism.
Growth of oocytes in the frog
The number of germ cells in the human ovary changes over the life span
End.