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Z Chromosome
The ZW sex-determination system is a chromosomal system that determines the sex of offspring in birds, some fish and crustaceans such as the giant river prawn, some insects (including butterflies and moths), the schistosome family of flatworms, and some reptiles, e.g. majority of snakes, lacertid lizards and monitors, including Komodo dragons. It is also present in some plants, where it has evolved independently on many occasions, characterizing at least 22% of plants with documented sex chromosomes. The letters Z and W are used to distinguish this system from the XY sex-determination system. In the ZW system, females have a pair of dissimilar ZW chromosomes, and males have two similar ZZ chromosomes. In contrast to the XY sex-determination system and the X0 sex-determination system, where the sperm determines the sex, in the ZW system, the ovum determines the sex of the offspring. Males are the homogametic sex (ZZ), while females are the heterogametic sex (ZW). The Z chromoso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Avian Sex Determination
Avian may refer to: *Anything related to birds (animals of the class ''Aves'') Aviation *Avro Avian, a series of light aircraft made by Avro in the 1920s and 1930s *Avian Limited, a hang glider manufacturer founded in 1989 Places *Avian, Iran, a village in Razavi Khorasan Province, Iran *, Friulian name of Aviano, a town and ''comune'' in northern Italy *Avian Island, Antarctica *Avian Tower, a high-rise building in Surabaya, Indonesia People *Avian (band), an American heavy metal band *Avian (given name), Russian male first name *Bob Avian (1937–2021), American choreographer and theater director See also * *Avian influenza, a virus adapted to birds *Evian, a brand of mineral water *Évian-les-Bains Évian-les-Bains (), or simply Évian (, , or ), is a Communes of France, commune in Eastern France, by the border with Switzerland. It is located in the northern part of the Haute-Savoie department in the Auvergne-Rhône-Alpes region. A high-m ..., a commune in eastern Fr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Autosomal
An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosomes is collectively known as atDNA or auDNA. For example, humans have a diploid genome that usually contains 22 pairs of autosomes and one allosome pair (46 chromosomes total). The autosome pairs are labeled with numbers (1–22 in humans) roughly in order of their sizes in base pairs, while allosomes are labelled with their letters. By contrast, the allosome pair consists of two X chromosomes in females or one X and one Y chromosome in males. Unusual combinations XYY, XXY, XXX, XXXX, XXXXX or XXYY, among other irregular combinations, are known to occur and usually cause developmental abnormalities. Autosomes still contain sexual determination genes even though they are not sex chromosomes. For example, the SRY gene on the Y chrom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pythonoidea
The Pythonoidea, also known as pythonoid snakes, are a superfamily of snakes that contains pythons (family Pythonidae) and other closely related python-like snakes (but not boas, which are in a separate superfamily called Booidea). As of 2022, Pythonoidea contains 39 species, including the eponymous genus '' Python'' and 10 other genera of pythons ('' Antaresia'', '' Apodora'', '' Aspidites'', '' Bothrochilus'', '' Leiopython'', '' Liasis'', '' Malayopython'', '' Morelia'', '' Nyctophilopthon'' and '' Simalia''), all in the family Pythonidae, as well as two lesser-known families, Loxocemidae (one species, the Mexican burrowing python, in the genus '' Loxocemus'') and Xenopeltidae (three species of sunbeam snakes in the genus '' Xenopeltis''). The taxonomy of pythons, boas, and other henophidian snakes has long been debated, and ultimately the decision whether to assign a particular clade to a particular Linnaean rank (such as a superfamily, family, or subfamily In biologi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Booidea
The Booidea, also known as booid snakes, are a superfamily of snakes that contains boas (family Boidae) and other closely related boa-like snakes (but not pythons, which are in a separate superfamily called Pythonoidea). As of 2017, Booidea contains 61 species, including the eponymous neotropical ''Boa constrictor'', anacondas (genus '' Eunectes''), and smaller tree and rainbow boas ('' Corallus'', '' Epicrates'', and '' Chilabothrus'') as well as several genera of booid snakes from various locations around the world: bevel-nosed boas or keel-scaled boas ('' Candoia'') from New Guinea and Melanesia, Old World sand boas ('' Eryx'') from Northeast Africa, the Middle East, and Southwest Asia, rubber boas (''Charina'') and rosy boas ('' Lichanura'') from North America, neotropical dwarf boas ('' Ungaliophis'') and the Oaxacan dwarf boa ('' Exiliboa'') from Central America, Madagascan boas or Malagasy boas ('' Acrantophis'' and '' Sanzinia'') from Madagascar, and the Calabar python (' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sex-link
Sex-links are crossbred chickens whose color at hatching is differentiated by sex, thus making chick sexing an easier process. Sex-links come in several varieties. As hybrids of laying or dual-purpose breeds infused with extra vigor via heterosis, sex-links can be extremely good egg-layers which often produce 300 eggs a year or more depending on the quality of care and feed. The color of their eggs vary according to the mix of breeds, and blue-green eggs are possible. Chicks of a single breed that are similarly sex-linked are called autosex chickens, a term developed to differentiate between sex linkage in purebred chickens versus sex linkage in crossbreeds. Sex-link types Many common varieties are known as the black sex-link (also called black stars) and the red sex-link (also called red stars). More specific variety names are common as well. * Black sex-link like "Black rocks" are a cross between unique specially bred hybrid strains of Rhode Island Red rooster (but any no ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DMRT1
Doublesex and mab-3 related transcription factor 1, also known as DMRT1, is a protein which in humans is encoded by the ''DMRT1'' gene. Function DMRT1 is a dose sensitive transcription factor protein that regulates Sertoli cells and germ cells. The DMRT1 gene is located at the end of the 9th chromosome. This gene is found in a cluster with two other members of the gene family, having in common a zinc finger-like DNA-binding motif (DM domain). The DM domain is an ancient, conserved component of the vertebrate sex-determining pathway that is also a key regulator of male development in flies and nematodes, and is found to be the key sex-determining factor in chickens. The majority of DMRT1 protein is located in the testicular cord and Sertoli cells, with a small amount in the germ cells. Defective testicular development and XY feminization occur when this gene is hemizygous Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Embryo
An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm cell. The resulting fusion of these two cells produces a single-celled zygote that undergoes many cell divisions that produce cells known as blastomeres. The blastomeres (4-cell stage) are arranged as a solid ball that when reaching a certain size, called a morula, (16-cell stage) takes in fluid to create a cavity called a blastocoel. The structure is then termed a blastula, or a blastocyst in mammals. The mammalian blastocyst hatches before implantating into the endometrial lining of the womb. Once implanted the embryo will continue its development through the next stages of gastrulation, neurulation, and organogenesis. Gastrulation is the formation of the three germ layers that will form all of the different parts of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dosage Compensation
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, female (XX) cells randomly silence the transcription of one X chromosome, and transcribe all information from the other, expressed X chromosome. Thus, human females have the same number of expressed X-linked genes per cell as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Therian Mammals
Theria ( or ; ) is a scientific classification, subclass of mammals amongst the Theriiformes. Theria includes the eutherians (including the Placentalia, placental mammals) and the metatherians (including the marsupials) but excludes the egg-laying monotremes and various extinct mammals evolving prior to the common ancestor of placentals and marsupials. Characteristics Therians give birth to live young without a shelled egg (biology), egg. This is possible thanks to key proteins called Syncytin-1, syncytins which allow exchanges between the mother and its offspring through a placenta, even Marsupial#Reproductive system, rudimental ones such as in marsupials. Genetic studies have suggested a viral origin of syncytins through the Endogenous retrovirus, endogenization process. The marsupials and the placentals evolved from a common therian ancestor that gave live birth by suppressing the mother's immune system. While the marsupials continued to give birth to an underdeveloped fe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meiosis
Meiosis () is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, the sperm or egg cells. It involves two rounds of division that ultimately result in four cells, each with only one copy of each chromosome (haploid). Additionally, prior to the division, genetic material from the paternal and maternal copies of each chromosome is crossed over, creating new combinations of code on each chromosome. Later on, during fertilisation, the haploid cells produced by meiosis from a male and a female will fuse to create a zygote, a cell with two copies of each chromosome. Errors in meiosis resulting in aneuploidy (an abnormal number of chromosomes) are the leading known cause of miscarriage and the most frequent genetic cause of developmental disabilities. In meiosis, DNA replication is followed by two rounds of cell division to produce four daughter cells, each with half the number of chromosomes as the original parent cell. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
