The germline is a cell line that passes on genetic inheritance to the next generation, including gametocytes and gametogonia. Somatic cells are not part of the germline, and mutations to somatic cells cannot be passed on. Germline gene therapy could make changes to the lineage of cells that contain genetic information that will be passed on. The germline provides information about heredity and can be used to examine relationships between different groups of individuals.
A germline is a cell line made up of cells used to pass on genetic inheritance to the next generation. Known as germ cells, these cells include gametocytes, which produce eggs and sperm, as well as eggs and sperm themselves, and gametogonia, cells that give rise to gametocytes. The germline is an unbroken hereditary chain that can be traced back many generations.
The germ line is present from the very beginning when an egg and a sperm fuse. As the cell begins to divide and develop into an embryo, the germ cells are specifically set aside; these cells will later generate eggs or sperm in the adult organism which will eventually become the embryo. Non-germ cells, known as somatic cells, will grow into various structures in the body. Somatic cells contain complete copies of the genome, but they differentiate to perform different functions, developing into neurons, muscle cells, bone cells, and so on.
Although somatic cells are derived from the germline, they are not part of it. Mutations to somatic cells cannot be passed on to future generations, while germline changes will be perpetuated. Some researchers have theorized that this could be valuable for gene-based therapies; in germline gene therapy, changes could be made to the lineage of cells that contain genetic information that will be passed on.
A mutation in the line will not affect the body of the organism in which the mutation occurs, but it will impact the organism’s offspring. For example, if a problem occurs during the production of egg or sperm cells and that particular egg or sperm cell becomes part of a zygote, this problem will impact the baby. A simple example of such a mutation is trisomy, in which someone inherits three chromosomes instead of two because two chromosomes failed to separate during egg or sperm production.
In addition to being of medical interest, the germline also provides a wealth of information about heredity. Changes can be tracked through it to learn more about an organism’s history, and this cell lineage can also be used to examine relationships between different groups of individuals. Humans, for example, share a common germline even though it has diverged in a wide variety of directions as new human generations have been born.
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