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X-linked Hypophosphatemia
X-linked hypophosphatemia (XLH) is an X-linked dominant form of rickets (or osteomalacia) that differs from most cases of dietary deficiency rickets in that vitamin D supplementation does not cure it. It can cause bone deformity including short stature and genu varum (bow-leggedness). It is associated with a mutation in the '' PHEX'' gene sequence (Xp.22) and subsequent inactivity of the PHEX protein. ''PHEX'' mutations lead to an elevated circulating (systemic) level of the hormone FGF23 which results in renal phosphate wasting, and locally in the extracellular matrix of bones and teeth an elevated level of the mineralization/calcification-inhibiting protein osteopontin. An inactivating mutation in the PHEX gene results in an increase in systemic circulating FGF23, and a decrease in the enzymatic activity of the PHEX enzyme which normally removes (degrades) mineralization-inhibiting osteopontin protein; in XLH, the decreased PHEX enzyme activity leads to an accumulation of inhibi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-linked Dominant
X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome. As an inheritance pattern, it is less common than the X-linked recessive type. In medicine, X-linked dominant inheritance indicates that a gene responsible for a genetic disorder is located on the X chromosome, and only one copy of the allele is sufficient to cause the disorder when inherited from a parent who has the disorder. In this case, someone who expresses an X-linked dominant allele will exhibit the disorder and be considered affected. X-linked dominant traits do not necessarily affect males more than females (unlike X-linked recessive traits). The exact pattern of inheritance varies, depending on whether the father or the mother has the trait of interest. All fathers that are affected by an X-linked dominant disorder will have affected daughters but not affected sons. However, if the mother is also affec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Delayed Growth
Child development involves the biological, psychological and emotional changes that occur in human beings between birth and the conclusion of adolescence. Childhood is divided into 3 stages of life which include early childhood, middle childhood, and late childhood (preadolescence). Early childhood typically ranges from infancy to the age of 6 years old. During this period, development is significant, as many of life's milestones happen during this time period such as first words, learning to crawl, and learning to walk. There is speculation that middle childhood/preadolescence or ages 6–12 are the most crucial years of a child's life. Adolescence is the stage of life that typically starts around the major onset of puberty, with markers such as menarche and spermarche, typically occurring at 12–13 years of age. It has been defined as ages 10 to 19 by the World Health Organization. In the course of development, the individual human progresses from dependency to increasing a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Male
Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilization. A male organism cannot reproduce sexually without access to at least one ovum from a female, but some organisms can reproduce both sexually and asexually. Most male mammals, including male humans, have a Y chromosome, which codes for the production of larger amounts of testosterone to develop male reproductive organs. Not all species share a common sex-determination system. In most animals, including humans, sex is determined genetically; however, species such as ''Cymothoa exigua'' change sex depending on the number of females present in the vicinity. In humans, the word ''male'' can also be used to refer to gender in the social sense of gender role or gender identity. Overview The existence of separate sexes has evolved independently at different times and in different lineages, an example ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Female
Female ( symbol: ♀) is the sex of an organism that produces the large non-motile ova (egg cells), the type of gamete (sex cell) that fuses with the male gamete during sexual reproduction. A female has larger gametes than a male. Females and males are results of the anisogamous reproduction system, wherein gametes are of different sizes, unlike isogamy where they are the same size. The exact mechanism of female gamete evolution remains unknown. In species that have males and females, sex-determination may be based on either sex chromosomes, or environmental conditions. Most female mammals, including female humans, have two X chromosomes. Female characteristics vary between different species with some species having pronounced secondary female sex characteristics, such as the presence of pronounced mammary glands in mammals. In humans, the word ''female'' can also be used to refer to gender in the social sense of gender role or gender identity. Etymology and usage ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Y Chromosome
The Y chromosome is one of two sex chromosomes (allosomes) in therian 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 determines the male or female sex of offspring produced in sexual reproduction. In mammals, the Y chromosome contains the gene SRY, which triggers male development. The DNA in the human Y chromosome is composed of about 59 million base pairs, making it similar in size to chromosome 19. 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. The human Y chromosome carries an estimated 100–200 genes, with between 45 and 73 of these being protein-coding. All single-copy Y-linked genes are hemizygous (present on only one chromosome) except in cases of aneuploidy such as XYY syndrome or XXYY syndrome. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sex Chromosome
A sex chromosome (also referred to as an allosome, heterotypical chromosome, gonosome, heterochromosome, or idiochromosome) 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. Nettie Stevens and Edmund Beecher Wilson both independently discovered sex chromosomes in 1905. However, Stevens is credited for discovering them earlier than Wilson. Differentiation In humans, each cell nucleus contains 23 pairs of chromosomes, a total of 46 chromosomes. The first 22 pairs are called autosomes. Autosomes are homologous chromosomes i.e. chromosomes which contain the same genes (regions of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Expressivity (genetics)
In genetics, expressivity is the degree to which a phenotype is expressed by individuals having a particular genotype. (Alternately, it may refer to the expression of particular gene by individuals having a certain phenotype.) Expressivity is related to the ''intensity'' of a given phenotype; it differs from penetrance, which refers to the ''proportion'' of individuals with a particular genotype that actually express the phenotype. Variable expressivity Variable expressivity refers to the degree in which a genotype is phenotypically expressed. For example, multiple people with the same disease can have the same genotype but one may express more severe symptoms, while another carrier may appear normal. This variation in expression can be affected by modifier genes, epigenetic factors or the environment. Modifier genes can alter the expression of other genes in either an additive or multiplicative way. Meaning the phenotype that is observed can be a result of two different alleles ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zygosity
Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism. Most eukaryotes have two matching sets of chromosomes; that is, they are diploid. Diploid organisms have the same loci on each of their two sets of homologous chromosomes except that the sequences at these loci may differ between the two chromosomes in a matching pair and that a few chromosomes may be mismatched as part of a chromosomal sex-determination system. If both alleles of a diploid organism are the same, the organism is homozygous at that locus. If they are different, the organism is heterozygous at that locus. If one allele is missing, it is hemizygous, and, if both alleles are missing, it is nullizygous. The DNA sequence of a gene often varies from one individual to another. These gene variants are called alleles. While some ge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypophosphatemia
Hypophosphatemia is an electrolyte disorder in which there is a low level of phosphate in the blood. Symptoms may include weakness, trouble breathing, and loss of appetite. Complications may include seizures, coma, rhabdomyolysis, or softening of the bones. Causes include alcohol use disorder, refeeding in those with malnutrition, recovery from diabetic ketoacidosis, burns, hyperventilation, and certain medications. It may also occur in the setting of hyperparathyroidism, hypothyroidism, and Cushing syndrome. It is diagnosed based on a blood phosphate concentration of less than 0.81 mmol/L (2.5 mg/dL). When levels are below 0.32 mmol/L (1.0 mg/dL) it is deemed to be severe. Treatment depends on the underlying cause. Phosphate may be given by mouth or by injection into a vein. Hypophosphatemia occurs in about 2% of people within hospital and 70% of people in the intensive care unit (ICU). Signs and symptoms * Muscle dysfunction and weakness – This occurs in major muscles, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fibroblast Growth Factor 23
Fibroblast growth factor 23 (FGF23) is a protein and member of the fibroblast growth factor (FGF) family which participates in the regulation of phosphate in plasma and vitamin D metabolism. In humans it is encoded by the gene. FGF23 decreases reabsorption of phosphate in the kidney. Mutations in ''FGF23'' can lead to its increased activity, resulting in autosomal dominant hypophosphatemic rickets. Description Fibroblast growth factor 23 (FGF23) is a protein which in humans is encoded by the gene. FGF23 is a member of the fibroblast growth factor (FGF) family which participates in phosphate and vitamin D metabolism and regulation. Function FGF23´s main function is to regulate the phosphate concentration in plasma. It does this by decreasing reabsorption of phosphate in the kidney, which means phosphate is excreted in urine. FGF23 is secreted by osteocytes in response to increased calcitriol. FGF23 acts on the kidneys by decreasing the expression of NPT2, a sodium/phosphate cot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X Chromosome
The X chromosome is one of the two sex-determining chromosomes (allosomes) in many organisms, including mammals (the other is the Y chromosome), and is found in both males and females. It is a part of the XY sex-determination system and XO sex-determination system. The X chromosome was named for its unique properties by early researchers, which resulted in the naming of its counterpart Y chromosome, for the next letter in the alphabet, following its subsequent discovery. Discovery It was first noted that the X chromosome was special in 1890 by Hermann Henking in Leipzig. Henking was studying the testicles of ''Pyrrhocoris'' and noticed that one chromosome did not take part in meiosis. Chromosomes are so named because of their ability to take up staining (''chroma'' in Greek means ''color''). Although the X chromosome could be stained just as well as the others, Henking was unsure whether it was a different class of object and consequently named it ''X element'', which later ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
