The Germ Line: Additional Concepts

Lange

BIOL 370 – Developmental Biology

Topic #19

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

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