- A nematode's genome, the genetic material encoded in DNA, is often similar to flatworms, annelids, and insects, but smaller than that of a molluscs or echinoderms genome.
- Nematodes genomes have a high rate of spontaneous deletions, which is one factor responsible for the genome's change in size.
- Repetition in the DNA sequence is also a cause of a nematode's change in size.
- Studies have shown that nematode species with a smaller number of individuals who can reproduce fertile offspring, have larger genomes, because they often have mutated DNA with duplications.
- Parasitic nematodes population size depends on their host organism. This means that nematodes produced within a herbivore have larger effective, able to reproduce, populations, than a population born within an omnivore or carnivore.
- Studies on nematodes from the same geographical area, show the species have very similar karyotypes.
- They all had the same gonad organization.
- Reproduction was found not to involve parthenogenesis.
- Spermatids are produced in adult females, and accumulated in the spermatheca before their is differentiation in gender.
- Spermatogenesis and oogenesis develop throughout a nematode's entire life.
- The image on the left represents different types of mutations in a nematodes ➡️
This image represents the developmental stages of a Nematoda. This is a process of several growing and molting stages. The growth of most nematode eggs happens within another host. For more on reproduction and the development of nematodes see Life Cycle.
Caenorhabditis elegans
This is a gif of a wild-type nematode, C. elegans, which is the first multicellular organism to have its entire genome sequenced and its connectome mapped. These are soil-living nematodes.
- C. elegans was studied because it has one of the simplest nervous systems.
- They explored the neural mechanisms that control many behaviors including chemotaxis, thermotaxis, mechanotransduction, and mating behavior.
- These multicellular eukaryotic organisms grow in population quick and simply which allow for them to be studied in great detail.
- The transparency of c. elegans helped to study cellular differentiation.
- The first cell divisions of early embryogenesis are examples of asymmetric cell division.
- Apoptosis, programmed cell death, helps to eliminate additional cells, that would become neurons.
- RNA interference is a method of disrupting the function of specific genes.
- Nematodes can be soaked or injected with a solution of double stranded RNA, which allows researchers to control specific functions.
- C. elegans DNA is approximately 100 million base pairs long.
- It has six chromosomes and a mitochondrial genome.
- Its gene density is one gene or five kilo-base pairs.
- Introns, non-expressed sequences, make up 26% of the genome.
- Some large intergenic regions have repetitive DNA sequences.
- Nematodes are among the few eukaryotes that have operons, which carry the information to translate into a polypeptide, and then protein.
- The genome has 20,470 protein-coding genes.
- 35% of C. elegans have human homologs, which are sometimes replaced by human genes.
- They also function similarly to mammalian genes.
- the genome is believed to contain more than 16,000 RNA genes, as of 2006.
- Nematodes have five pairs of autosomes and one pair of sex chromosomes.
- Nematode hermaphrodites have two X chromosomes and males have one X chromosome.
- Wild type nematodes have a consistently have 959 cells.
- Nematodes were studied for their aging, for their insulin-like growth factor, which signals a development in increase adult lifespan.
- Nematodes were studied in the International Space Station, to explore the effects of zero graviton muscle development and physiology.