Germline
Encyclopedia
In biology
and genetics
, the germline of a mature or developing
individual is the line (sequence) of germ cell
s that have genetic material that may be passed to a child.
For example, gamete
s such as the sperm or the egg
, are part of the germline. So are the cells that divide to produce the gametes, called gametocyte
s, the cells that produce those, called gametogonia
, and all the way back to the zygote
, the cell from which the individual developed.
Cells that are not in the germline are called somatic cell
s. This refers to all of the cells of body apart from the gametes. If there is a mutation
or other genetic change in the germline, it can potentially be passed to offspring, but a change in a somatic cell will not be.
Germline cells are immortal, in the sense that they have the potential to reproduce indefinitely. This is largely due to the activity of the enzyme
known as telomerase
. This enzyme extends the telomeres of the chromosome
, preventing chromosome fusions and other negative effects of shortened telomeres. Most somatic cells, by comparison, can only divide around 30-50 times according to the Hayflick limit
. Certain somatic cells, known as stem cells, also express telomerase
and are potentially immortal.
Not all multicellular organisms differentiate cells into somatic and germ lines. Notably, plants have no germline cells separate from stem cells.
Germline can refer to a lineage of cells spanning many generations of individuals—for example, the germline that links any living individual to the hypothetical first eukaryote
of about 2 billion years ago, from which all plants and animals descend
.
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...
and genetics
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
, the germline of a mature or developing
Morphogenesis
Morphogenesis , is the biological process that causes an organism to develop its shape...
individual is the line (sequence) of germ cell
Germ cell
A germ cell is any biological cell that gives rise to the gametes of an organism that reproduces sexually. In many animals, the germ cells originate near the gut of an embryo and migrate to the developing gonads. There, they undergo cell division of two types, mitosis and meiosis, followed by...
s that have genetic material that may be passed to a child.
For example, gamete
Gamete
A gamete is a cell that fuses with another cell during fertilization in organisms that reproduce sexually...
s such as the sperm or the egg
Ovum
An ovum is a haploid female reproductive cell or gamete. Both animals and embryophytes have ova. The term ovule is used for the young ovum of an animal, as well as the plant structure that carries the female gametophyte and egg cell and develops into a seed after fertilization...
, are part of the germline. So are the cells that divide to produce the gametes, called gametocyte
Gametocyte
A gametocyte is a eukaryotic germ cell that divides by mitosis into other gametocytes or by meiosis into gametids during gametogenesis. Male gametocytes are called spermatocytes, and female gametocytes are called oocytes....
s, the cells that produce those, called gametogonia
Gametogonium
A gametogonium is a germ cell that divides into gametocytes during gametogenesis. Male gametogonia are called spermatogonia, and female gametogonia are called oogonia....
, and all the way back to the zygote
Zygote
A zygote , or zygocyte, is the initial cell formed when two gamete cells are joined by means of sexual reproduction. In multicellular organisms, it is the earliest developmental stage of the embryo...
, the cell from which the individual developed.
Cells that are not in the germline are called somatic cell
Somatic cell
A somatic cell is any biological cell forming the body of an organism; that is, in a multicellular organism, any cell other than a gamete, germ cell, gametocyte or undifferentiated stem cell...
s. This refers to all of the cells of body apart from the gametes. If there is a mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
or other genetic change in the germline, it can potentially be passed to offspring, but a change in a somatic cell will not be.
Germline cells are immortal, in the sense that they have the potential to reproduce indefinitely. This is largely due to the activity of the enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
known as telomerase
Telomerase
Telomerase is an enzyme that adds DNA sequence repeats to the 3' end of DNA strands in the telomere regions, which are found at the ends of eukaryotic chromosomes. This region of repeated nucleotide called telomeres contains non-coding DNA material and prevents constant loss of important DNA from...
. This enzyme extends the telomeres of the chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
, preventing chromosome fusions and other negative effects of shortened telomeres. Most somatic cells, by comparison, can only divide around 30-50 times according to the Hayflick limit
Hayflick limit
The Hayflick limit is the number of times a normal cell population will divide before it stops, presumably because the telomeres reach a critical length....
. Certain somatic cells, known as stem cells, also express telomerase
Telomerase
Telomerase is an enzyme that adds DNA sequence repeats to the 3' end of DNA strands in the telomere regions, which are found at the ends of eukaryotic chromosomes. This region of repeated nucleotide called telomeres contains non-coding DNA material and prevents constant loss of important DNA from...
and are potentially immortal.
Not all multicellular organisms differentiate cells into somatic and germ lines. Notably, plants have no germline cells separate from stem cells.
Germline can refer to a lineage of cells spanning many generations of individuals—for example, the germline that links any living individual to the hypothetical first eukaryote
Eukaryote
A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...
of about 2 billion years ago, from which all plants and animals descend
Common descent
In evolutionary biology, a group of organisms share common descent if they have a common ancestor. There is strong quantitative support for the theory that all living organisms on Earth are descended from a common ancestor....
.
See also
- August WeismannAugust WeismannFriedrich Leopold August Weismann was a German evolutionary biologist. Ernst Mayr ranked him the second most notable evolutionary theorist of the 19th century, after Charles Darwin...
- EpigeneticsEpigeneticsIn biology, and specifically genetics, epigenetics is the study of heritable changes in gene expression or cellular phenotype caused by mechanisms other than changes in the underlying DNA sequence – hence the name epi- -genetics...
- Weismann barrierWeismann barrierThe Weismann barrier is the principle that hereditary information moves only from genes to body cells, and never in reverse. In more precise terminology hereditary information moves only from germline cells to somatic cells .This does not refer to the central dogma of molecular biology which...
- Germ line developmentGerm line developmentThe cells that give rise to the gametes are often set aside during cleavage. During development, these cells will differentiate into primordial germ cells, migrate to the location of the gonad, and form the germ line of the animal....