X0 sex-determination system
Encyclopedia
The X0 sex-determination system is a system that hymenoptera
ns, grasshopper
s, cricket
s, cockroaches
, and some other insects use to determine the sex of their offspring. In this system, there is only one sex chromosome, referred to as X. Males only have one X chromosome (X0), while females have two (XX). The zero (sometimes, the letter O) signifies the lack of a second X maternal gametes always contain an X chromosome, so the sex of the animals' offspring is decided by the male. Its sperm
normally contain either one X chromosome or no sex chromosomes at all.
In a variant of this system, certain animals are hermaphroditic
with two sex chromosomes (XX) and male with only one (X0). The model organism
Caenorhabditis elegans
— a nematode
frequently used in biological research — is one such organism.
Some Drosophila
species have X0 males. These are thought to arise via the loss of the Y chromosome
.
. However, such individuals generally present as female
, as humans have an XY sex-determination system
.
Hymenoptera
Hymenoptera is one of the largest orders of insects, comprising the sawflies, wasps, bees and ants. There are over 130,000 recognized species, with many more remaining to be described. The name refers to the heavy wings of the insects, and is derived from the Ancient Greek ὑμήν : membrane and...
ns, grasshopper
Grasshopper
The grasshopper is an insect of the suborder Caelifera in the order Orthoptera. To distinguish it from bush crickets or katydids, it is sometimes referred to as the short-horned grasshopper...
s, cricket
Cricket (insect)
Crickets, family Gryllidae , are insects somewhat related to grasshoppers, and more closely related to katydids or bush crickets . They have somewhat flattened bodies and long antennae. There are about 900 species of crickets...
s, cockroaches
Cockroaches
A cockroach is an insect of the order Blattaria. "Cockroach" may also refer to:*Cockroach , a 2001 album by Danger Danger*Cockroach , a 2008 novel by Rawi Hage...
, and some other insects use to determine the sex of their offspring. In this system, there is only one sex chromosome, referred to as X. Males only have one X chromosome (X0), while females have two (XX). The zero (sometimes, the letter O) signifies the lack of a second X maternal gametes always contain an X chromosome, so the sex of the animals' offspring is decided by the male. Its sperm
Spermatozoon
A spermatozoon is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote...
normally contain either one X chromosome or no sex chromosomes at all.
In a variant of this system, certain animals are hermaphroditic
Hermaphrodite
In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...
with two sex chromosomes (XX) and male with only one (X0). The model organism
Model organism
A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to...
Caenorhabditis elegans
Caenorhabditis elegans
Caenorhabditis elegans is a free-living, transparent nematode , about 1 mm in length, which lives in temperate soil environments. Research into the molecular and developmental biology of C. elegans was begun in 1974 by Sydney Brenner and it has since been used extensively as a model...
— a nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
frequently used in biological research — is one such organism.
Some Drosophila
Drosophila
Drosophila is a genus of small flies, belonging to the family Drosophilidae, whose members are often called "fruit flies" or more appropriately pomace flies, vinegar flies, or wine flies, a reference to the characteristic of many species to linger around overripe or rotting fruit...
species have X0 males. These are thought to arise via the loss of the Y chromosome
Y chromosome
The Y chromosome is one of the two sex-determining chromosomes in most mammals, including humans. In mammals, it contains the gene SRY, which triggers testis development if present. The human Y chromosome is composed of about 60 million base pairs...
.
In humans
In humans, having only a single X chromosome is known as Turner syndromeTurner syndrome
Turner syndrome or Ullrich-Turner syndrome encompasses several conditions in human females, of which monosomy X is most common. It is a chromosomal abnormality in which all or part of one of the sex chromosomes is absent...
. However, such individuals generally present as female
Female
Female is the sex of an organism, or a part of an organism, which produces non-mobile ova .- Defining characteristics :The ova are defined as the larger gametes in a heterogamous reproduction system, while the smaller, usually motile gamete, the spermatozoon, is produced by the male...
, as humans have an XY sex-determination system
XY sex-determination system
The XY sex-determination system is the sex-determination system found in humans, most other mammals, some insects and some plants . In this system, females have two of the same kind of sex chromosome , and are called the homogametic sex. Males have two distinct sex chromosomes , and are called...
.
See also
- X chromosomeX chromosomeThe X chromosome is one of the two sex-determining chromosomes in many animal species, including mammals and is common in both males and females. It is a part of the XY sex-determination system and X0 sex-determination system...
- Y chromosomeY chromosomeThe Y chromosome is one of the two sex-determining chromosomes in most mammals, including humans. In mammals, it contains the gene SRY, which triggers testis development if present. The human Y chromosome is composed of about 60 million base pairs...
- chromosomeChromosomeA 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...
- sexual differentiationSexual differentiationSexual differentiation is the process of development of the differences between males and females from an undifferentiated zygote...
- Sex-determination systemSex-determination systemA sex-determination system is a biological system that determines the development of sexual characteristics in an organism. Most sexual organisms have two sexes. In many cases, sex determination is genetic: males and females have different alleles or even different genes that specify their sexual...
- XY sex-determination systemXY sex-determination systemThe XY sex-determination system is the sex-determination system found in humans, most other mammals, some insects and some plants . In this system, females have two of the same kind of sex chromosome , and are called the homogametic sex. Males have two distinct sex chromosomes , and are called...
- ZW sex-determination systemZW sex-determination systemThe ZW sex-determination system is a system that determines the sex of offspring in birds, some fish and crustaceans such as the giant river prawn, some insects , and some reptiles, including Komodo dragons...
- Haplodiploid sex-determination system
- XY sex-determination system