Metafemale

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A metafemale (or superfemale) is a low viability Drosophila fruit fly with a female phenotype in which the ratio of X chromosomes to sets of autosomes (A) exceeds 1.0. [1] For example: a fly with one X chromosome and two sets of autosomes is a normal male, a fly with two X chromosomes and two sets of autosomes is a normal female, and a fly with three X chromosomes and two sets of autosomes (or four X chromosomes and three sets of autosomes) is a metafemale.

<i>Drosophila</i> genus of insects

Drosophila is a genus of flies, belonging to the family Drosophilidae, whose members are often called "small fruit flies" or pomace flies, vinegar flies, or wine flies, a reference to the characteristic of many species to linger around overripe or rotting fruit. They should not be confused with the Tephritidae, a related family, which are also called fruit flies ; tephritids feed primarily on unripe or ripe fruit, with many species being regarded as destructive agricultural pests, especially the Mediterranean fruit fly. One species of Drosophila in particular, D. melanogaster, has been heavily used in research in genetics and is a common model organism in developmental biology. The terms "fruit fly" and "Drosophila" are often used synonymously with D. melanogaster in modern biological literature. The entire genus, however, contains more than 1,500 species and is very diverse in appearance, behavior, and breeding habitat.

Phenotype classification system used to categorize organisms based on their appearance

The phenotype of an organism is the composite of the organism's observable characteristics or traits, including its morphology or physical form and structure; its developmental processes; its biochemical and physiological properties; its behavior, and the products of behavior, for example, a bird's nest. An organism's phenotype results from two basic factors: the expression of an organism's genetic code, or its genotype, and the influence of environmental factors, which may interact, further affecting phenotype. When two or more clearly different phenotypes exist in the same population of a species, the species is called polymorphic. A well-documented polymorphism is Labrador Retriever coloring; while the coat color depends on many genes, it is clearly seen in the environment as yellow, black and brown. Richard Dawkins in 1978 and then again in his 1982 book The Extended Phenotype suggested that bird nests and other built structures such as caddis fly larvae cases and beaver dams can be considered as "extended phenotypes".

Autosome Any chromosome other than a sex chromosome.

An autosome is a chromosome that is not an allosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosome pairs which may have different structures. The DNA in autosomes is collectively known as atDNA or auDNA.

American geneticist Calvin Bridges, who discovered the genic balance sex-determination system in Drosophila in 1921, used the terms "superfemale" and "supermale". [2] German-American geneticist Curt Stern proposed the alternative terms "metafemale" and "metamale" in 1959. [3]

Calvin Blackman Bridges was an American scientist known for his contributions to the field of genetics. Along with Alfred Sturtevant and H.J. Muller, Bridges was part of Thomas Hunt Morgan's famous "Fly Room" at Columbia University.

Sex-determination system A biological system that determines the development of sexual characteristics in an organism

A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. Most organisms that create their offspring using sexual reproduction have two sexes. Occasionally, there are hermaphrodites in place of one or both sexes. There are also some species that are only one sex due to parthenogenesis, the act of a female reproducing without fertilization.

Curt Stern was a German-born American geneticist.

Related Research Articles

<i>Drosophila melanogaster</i> Species of fruit fly

Drosophila melanogaster is a species of fly in the family Drosophilidae. The species is known generally as the common fruit fly or vinegar fly. Starting with Charles W. Woodworth's proposal of the use of this species as a model organism, D. melanogaster continues to be widely used for biological research in genetics, physiology, microbial pathogenesis, and life history evolution. As of 2017, eight Nobel prizes had been awarded for research using Drosophila.

Y chromosome The sex chromosome present in males of species in which the male is the heterogametic sex; generally, the sex chromosome that pairs with the X chromosome in the heterogametic sex. The Y chromosome is absent from the cells of females and present in on

The Y chromosome is one of two sex chromosomes (allosomes) in mammals, including humans, and many other animals. The other is the X chromosome. Y is normally the sex-determining chromosome in many species, since it is the presence or absence of Y that typically determines the male or female sex of offspring produced in sexual reproduction. In mammals, the Y chromosome contains the gene SRY, which by default triggers male development. The DNA in the human Y chromosome is composed of about 59 million base pairs. The Y chromosome is passed only from father to son. With a 30% difference between humans and chimpanzees, the Y chromosome is one of the fastest-evolving parts of the human genome. To date, over 200 Y-linked genes have been identified. All Y-linked genes are expressed and hemizygous except in the cases of aneuploidy such as XYY syndrome or XXYY syndrome.

Haldanes rule

Haldane's rule is an observation about the early stage of speciation, formulated in 1922 by the British evolutionary biologist J.B.S. Haldane, that states that if in a species hybrid only one sex is inviable or sterile, that sex is more likely to be the heterogametic sex. The heterogametic sex is the one with two different sex chromosomes; in therian mammals, for example, this is the male.

Triple X syndrome

Triple X syndrome, also known as trisomy X and 47,XXX, is characterized by the presence of an extra X chromosome in each cell of a female. Those affected are often taller than average. Usually there are no other physical differences and normal fertility. Occasionally there are learning difficulties, decreased muscle tone, seizures, or kidney problems.

Sex linkage the sex-specific patterns of inheritance and presentation when a gene mutation is present on a sex chromosome rather than a non-sex chromosome

Sex linkage is the patterns of inheritance and presentation when a gene mutation (allele) is present on a sex chromosome (allosome) rather than a non-sex chromosome (autosome). They are characteristically different from the autosomal forms of dominance and recessiveness as they are different depending on the sex of the individual.

Dosage compensation Compensating for the variation in the unpaired sex chromosome:autosome chromosome ratios between sexes by activation or inactivation of genes on one or both of the sex chromosomes.

Dosage compensation is the process by which organisms equalize the expression of genes between members of different biological sexes. Across species, different sexes are often characterized by different types and numbers of sex chromosomes. In order to neutralize the large difference in gene dosage produced by differing numbers of sex chromosomes among the sexes, various evolutionary branches have acquired various methods to equalize gene expression among the sexes. Because sex chromosomes contain different numbers of genes, different species of organisms have developed different mechanisms to cope with this inequality. Replicating the actual gene is impossible; thus organisms instead equalize the expression from each gene. For example, in humans, females (XX) silence the transcription of one X chromosome of each pair, and transcribe all information from the other, expressed X chromosome. Thus, human females have the same number of expressed X-linked genes as do human males (XY), both sexes having essentially one X chromosome per cell, from which to transcribe and express genes.

Genetics, a discipline of biology, is the science of heredity and variation in living organisms.

X hyperactivation

X hyperactivation refers to the process in Drosophila by which genes on the X chromosome in male flies become twice as active as genes on the X chromosome in female flies.

The X:A ratio is the ratio between the number of X chromosomes and the number of sets of autosomes in an organism. This ratio is used primarily for determining the sex of some species, such as drosophila flies and the C. elegans nematode. The first use of this ratio for sex determination is ascribed to Victor M. Nigon.

Haplodiploidy biological system in which sex is determined by the number of sets of chromosomes

Haplodiploidy is a sex-determination system in which males develop from unfertilized eggs and are haploid, and females develop from fertilized eggs and are diploid. Haplodiploidy is sometimes called arrhenotoky.

Heterogametic sex sex of a species in which the sex chromosomes are not the same; e.g. human males (with XY chromosomes); bird females (with ZW chromosomes)

Heterogametic sex refers to the sex of a species in which the sex chromosomes are not the same. For example, in humans, males, with an X and a Y sex chromosome, would be referred to as the heterogametic sex, and females having two X sex chromosomes would be referred to as the homogametic sex.

A metamale is a low viability Drosophila fruit fly with a male phenotype in which the ratio of X chromosomes to sets of autosomes (A) is less than 0.5. For example: a fly with one X chromosome and two sets of autosomes is a normal male, a fly with one X chromosome and three sets of autosomes is a metamale.

Sex chromosome A chromosome involved in sex determination.

An allosome is a chromosome that differs from an ordinary autosome in form, size, and behavior. The human sex chromosomes, a typical pair of mammal allosomes, determine the sex of an individual created in sexual reproduction. Autosomes differ from allosomes because autosomes appear in pairs whose members have the same form but differ from other pairs in a diploid cell, whereas members of an allosome pair may differ from one another and thereby determine sex.

Sexual differentiation in humans the process of development of sex differences in humans

Sexual differentiation in humans is the process of development of sex differences in humans. It is defined as the development of phenotypic structures consequent to the action of hormones produced following gonadal determination. Sexual differentiation includes development of different genitalia and the internal genital tracts, breasts, body hair, and plays a role in gender identification.

The concept of a biological species as a group of organisms capable of interbreeding to produce viable offspring dates back to at least the 18th century, although it is often associated today with Ernst Mayr. Species of the fruit-fly Drosophila are one of the most commonly used organisms in evolutionary research, and have been used to test many theories related to the evolution of species. The genus Drosophila comprises numerous species that have varying degrees of premating and postmating isolation between them. These species are useful for testing hypotheses of the reproductive mechanisms underlying speciation.

References

  1. ↑ King, Robert C.; Mulligan, Pamela Khipple; Stansfield, William D. (2013). A dictionary of genetics (8th ed.). Oxford: Oxford University Press. pp. 189, 288, 458. ISBN   978-0-19-976643-7.
    genic balance: a mechanism of sex determination, originally discovered in Drosophila, that depends on the ratio of X chromosomes to sets of autosomes (A). Males develop when the X/A ratio is 0.5 or less, females develop when the X/A ratio is 1.0 or greater, an intersex develops when the ratio is between 0.5 and 1.0. See Appendix C, 1925, Bridges; metafemales, metamales, sex determination.
    metafemale: in Drosophila, a female phenotype of relatively low viability in which the ratio of X chromosomes to sets of autosomes exceeds 1.0, previously called a superfemale. See intersex, metamale.
    metamale: in Drosophila, a poorly viabile male characterized by cells containing one X and three sets of autosomes, previously called a supermale. See intersex, metafemale.
    superfemale: metafemale (q.v.).
    supermale: metamale (q.v.).
  2. ↑ Bridges, Calvin B. (September 16, 1921). "Triploid intersexes in Drosophila melanogaster" (PDF). Science . 54 (1394): 252–254. doi:10.1126/science.54.1394.252. JSTOR   1646022. PMID   17769897.
  3. ↑ Stern, Curt (December 12, 1959). "Use of the term 'superfemale'". Lancet . 274 (7111): 1088. doi:10.1016/S0140-6736(59)91557-0.
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