The Germ Line: Additional Concepts

1
The Germ Line Additional Concepts
BIOL 370 Developmental Biology Topic 19

• Lange

2

• 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)

3
Pole plasm of Drosophila
Here, we see Pole Cells (both AB) associated
with Drosophila.
4
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.
5
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.
6
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.
7
Growth of oocytes in the frog
8
The number of germ cells in the human ovary
changes over the life span
9
(No Transcript)
10
End.