Primordium Germ Cell part 1

Summary

This video explains the concept of primordial germ cells (PGCs), which are the precursors to gametes—sperm and egg cells. PGCs differentiate and eventually fuse to form a zygote, leading to the development of a new individual. The transcript discusses the migration of these cells in different species, such as vertebrates and invertebrates, and the molecular markers associated with PGCs, like alkaline phosphatase in mammals and glycogen synthase in birds. Additionally, it highlights the role of plasma germinal factors that guide cell development, particularly in species like drosophila and nematodes, showing how specific proteins ensure proper germ cell differentiation.

Takeaways

• 😀 The primordia cell (germinal precursor cells) will develop into germ cells, which differentiate into gametes—sperm for males and ovum for females.
• 😀 Germ cells play a crucial role in sexual reproduction by connecting the parental generation with the next, passing on genetic information.
• 😀 In vertebrates (such as reptiles, amphibians, and mammals), germ cells are located in the gonads, while in invertebrates (like earthworms and insects), germ cells also develop in the gonads.
• 😀 In some animals, primordial germ cells originate outside the gonads and migrate to complete their development.
• 😀 Early development in vertebrates shows a clear distinction between germ cells and somatic cells, while in some invertebrates, somatic cells can transform into germ cells even after the organism reaches adulthood.
• 😀 In species like Hydra and jellyfish, somatic cells can detach and become gametes, illustrating a unique developmental process.
• 😀 Hydra’s life cycle includes both vegetative (polyp) and generative (Medusa) phases, with Medusa producing male and female gametes.
• 😀 Molecular markers help distinguish germ cells, with mammals using alkaline phosphatase and other species like birds using glycogen synthetase to identify germ cells.
• 😀 Plasma germinal, composed of specific proteins and mRNA, is localized in certain areas of embryos and guides surrounding cells to become germ cells.
• 😀 Studies in nematodes like *Ascaris* show how plasma germinal influences chromosome preservation and cell differentiation in germ cells, with significant differences in cell division patterns.

Q & A

What are primordial germ cells and what is their significance in sexual reproduction?

Primordial germ cells are the precursor cells that eventually develop into germ cells. These germ cells differentiate into gametes (sperm or eggs), which combine during fertilization to form a zygote, leading to the development of a new organism. They play a crucial role in transferring genetic material from one generation to the next in sexually reproducing organisms.

Where are primordial germ cells located in vertebrates and invertebrates?

In vertebrates, such as reptiles, amphibians, and mammals, primordial germ cells are located in the gonads. In invertebrates like earthworms and insects, these cells are also found in the gonads.

How do primordial germ cells differ between vertebrates and some invertebrates?

In vertebrates, primordial germ cells are separated early from somatic cells, with a clear distinction between the two. In some invertebrates like Hydra and jellyfish, somatic cells can transform into germ cells, even in adulthood, which is not the case for vertebrates.

What role does plasma germinal play in germ cell development?

Plasma germinal consists of specific proteins and mRNA that guide certain cells in the embryo to develop into germ cells. This plasma is localized in specific areas of the embryo and directs surrounding cells to differentiate into primordial germ cells.

How does the gene 'Gisel' contribute to germ cell development in Drosophila?

The gene 'Gisel' in Drosophila plays a key role in stimulating centrosome aggregation, which is necessary for the formation of germ cells. Without the proper function of this gene, germ cells cannot develop.

What is the significance of molecular markers in identifying primordial germ cells?

Molecular markers are specific molecules found only in primordial germ cells and not in other cells. These markers, like alkaline phosphatase in mammals or glycogen synthetase in birds, help identify and confirm the presence of germ cells.

How do primordial germ cells migrate in certain organisms?

In some species, primordial germ cells originate outside the gonads and must migrate to the developing gonads to complete their development. This migration is essential for their proper differentiation into gametes.

What happens to the chromosomes of cells without plasma germinal in the nematode Parascaris?

In the nematode Parascaris, cells that lack plasma germinal undergo chromosomal fragmentation, resulting in the reduction of chromosome size. In contrast, cells with plasma germinal maintain intact chromosomes.

What is the difference between somatic and germ cell differentiation in Hydra?

In Hydra, somatic cells can transform into germ cells during the adult phase, a process not commonly seen in vertebrates. This allows Hydra to reproduce sexually through the development of gametes from somatic cells.

What is the relationship between the development of Medusa and gametogenesis in Hydrozoa?

In Hydrozoa, the Medusa stage is part of the organism's generative phase. During this phase, Medusa develops gametes (sperm and eggs). These gametes combine to form a zygote, which eventually develops into a new individual in the life cycle of Hydrozoa.